User:Eggiehi/Temp/Overview124.doc

Overview

= What is A & P? =

Anatomy: How the body is put together — its organization.
One characteristic shared by all living things, though, is hierarchical organization. We’ll find it useful to look at the body using this hierarchy as a guide.

Chemical
the level of atoms and molecules; at this level, principles of chemistry and physics are most important. This seems like it’s outside the scope of this course, but it’s very important - all of physiology eventually depends on chemical reactions. You need to know at least a little of this to understand the rest of what’s going on.

Cellular
the level of cells, which are structures made of highly organized groups of molecules. As a general rule, you can say that the cell is the fundamental unit of living things - all living things are cells or made up of cells. Single celled organisms have to have one cell do everything - a ‘jack of all trades’ cell. Larger organisms have the ability/necessity of allowing cells to specialize for certain funtions.

Tissue
Groups of cells, organized to perform a specific function, are called tissues; for example, muscle tissue, nervous tissue, connective tissue. Tissues are the building blocks used to put together large, multicellular organisms like people.

Organ
Groups of tissues, organized to perform a specific function, are called organs. The tissues in an organ each perform the roles typical for that tissue; but the result is that the organ can perform complex roles that would be impossible for the tissues by themselves, for example the stomach. But the stomach by itself is not very useful - it has to be connected to a set of other organs to work.

System
Groups of organs, organized to perform a specific function - the digestive system as an example. As a whole, the system is responsible for getting energy into the body; this means it has individual parts (organs) that are responsible for ingesting food, breaking it down (mechanically and chemically), absorbing nutrients, detoxifying (some) bad chemicals, and getting rid of what’s not usable by the body.

Organism
Groups of organ systems, organized to perform a specific function - to be a complete, functioning organism (in this case, a human being). Just as an organ by itself is not very useful without the other organs that support it, an organ system is not independent of the other organ systems of the body. For us, what that really means is that what happens in one system is almost never just restricted to that one system - the effects ripple outward to many other systems as well.

Physiology: how the structures of the body function (at all levels of organization).
Physiology is the study of the principal processes of life:

Metabolism
a general term that covers all the chemical changes and reactions that occur within the body; the chemistry that controls the day-to-day business of living. this covers digestion, respiration, synthesis, excretion, etc.

Irritability / Responsiveness
the ability to detect and respond to changes in the (internal or external) environment. This happens at many structural levels - cells detect & respond to changes in extracellular fluid, organs can respond to changes outside the body (or to instructions from the nervous or endocrine systems), the organism as a whole can respond to internal or external events.

Growth
generally, we mean an increase in size because of an increase in cell number or cell-produced materials.

Differentiation
the changes that cells and tissues undergo as they divide and mature. in general, cells (or cell lineages) and tissues start out unspecialized, then become increasingly specialized as time goes on.

Reproduction
in this case, reproduction occurs at 2 distinct levels: most of our cells reproduce repeatedly throughout our lifetimes (producing cell lineages) and in addition, the organism as a whole is capable of reproduction, though in this case additional help is required.

What is it?
You, as an organism, can operate at a wide range of conditions.

Your cells, however, cannot.

Maintenance of internal environment...
Environments:

External — outside the body

Extracellular — fluids outside the individual cells

Intracellular — internal cell environment

...at the optimal range of conditions. — the body can tolerate successively less environmental variation in each of the above environments.
What sort of conditions must be controlled?pH — 6.8 - 7.3% H2Oion concentrations (0.9 % saline)oxygennutrientstemperaturewastes

Homeostasis is maintained by feedback systems ( = system where effect changes control of effect)
nervous & endocrine systs. main actors here.

negative feedback: — thermoregulation, blood sugar

positive feedback: — labor - stretching uterus causes release of oxytocin, causes contraction, causes more stretching...

Terminology
body regionsFig. 1.5directional termsExhibit 1.3

planes Figure 1.7, 1.8cavitiesFigure 1.9

quadrantChemical Background

= Energy - “the ability to do work” = as the saying goes, it can not be created or destroyed — but it can be converted from one form to another. We can categorize energy by what it’s doing:

Potential vs. kinetic energy
Potential energy is stored energy.Kinetic energy is the energy spent doing work.

Forms of energy:
Radiant — energy of the electromagnetic spectrum; kineticElectrical — energy from the flow of charged particles; potential & kineticHeat — energy from the vibration of atoms and molecules; potential & kineticChemical — energy contained within chemical bonds; potentialMechanical — energy from the movement of objects; potential & kinetic

= Elements (exhibit 2.1) =

= Atomic Structure and Valence =

Electron shells - pairs of electrons - valence
= Chemical Bonds: =

Ionic
Transfer of electrons — results in ions which dissociate in H2O (easily dissolved), polar

cation - +-charge; anion - --charge

Covalent
Sharing of electrons — not ionic; does not dissociate; may or may not be polarsingle, double, triple bonds

Hydrogen — weak bonds between covalently-bonded H and another covalently-bonded atom
= Chemical Reactions (review starting on pg. 32) =

Decomposition (catabolic)
= Compounds = compounds are combinations of 2 or more different elements. They can be divided into 2 categories, inorganic and organic.

Inorganic compounds
Compounds that do not contain C and H. Many inorganic substances dissolve into ions. In general, most inorganic molecules that we are concerned with will fall into one of the following 4 categories.

Acids
an acid is a substance which, when it dissolves, increases the amount of H+ ions in solution. it may do this directly, by adding more H+ to the solution (HCl  H+ + Cl- ) or indirectly, by reducing the amounts of OH- in solution (proteins & amino acids may do this*). *Note: organic compounds can be acids (and bases) too!!!

Bases
a base is a substance which, when it dissolves, decreases the amount of H+ ions in solution. Most often, it will do this by adding OH- ions to the solution, which will combine with the H+ ions to form water (NaOH  Na+ + OH- ; OH - + H+  H2O ). Other negatively-charged ions will work as well (H+ + NaHCO3  Na+ + H2CO3  H2O + CO2).

H+ and OH- ions are very, very reactive- they tend to interfere with other molecules. That’s why solutions that have lots of one or the other (HCl, NaOH) are dangerous. H+ and OH- combine with each other to form water, so if you have lots of both, nothing much will happen. In fact, pure water is a combination of H2O, H+, and OH-. The scale that measures the imbalance of H+ and OH- is the pH scale. Strictly speaking, pH is the

Salts
a salt is a substance that dissolves into + and - particles (ions), neither of which is H+or OH-. Many of these ions are vitally important to physiological processes in the body (NaCl  Na+ + Cl- ; NaHCO 3  Na+ + HCO3- ; other important ions - Ca++, K+)

H2O
 70% of body weight; some important chemical properties —

solvent for other chemicals.
water is a very good solvent; a wide range of materials will dissolve, at least slightly, in water. solutions can be ionic (like NaCl in solution) or molecular (like glucose in solution).

Water’s secret is its polarity. This means that each water molecule acts like a little battery, with a - pole and a + pole. These are not ‘complete’ + and - charges, so they are indicated with a  symbol in front: +, -. These differently-charged ‘poles’ of the molecules are attracted to and can surround (and therefore dissolve) other substances whose molecules have + and - regions (and are themselves ‘polar’).

Even when water can’t dissolve something, it often is very good at suspending it; that is, it can keep materials floating around without letting them clump together - for a while, at least.

Most important chemical reactions in the body take place in an aqueous environment.

vital component of some important reactions
two important examples — dehydration synthesis, hydrolysis

high heat capacity
it takes a lot of energy to raise the temperature of water; it is an excellent buffer for heat. that enables it to help the body maintain temperature homeostasis.

a related property is water’s:

high heat of vaporization
this means the amount of energy required to evaporate liquid water. (it’s a lot of energy). this is why evaporating sweat can be an effective cooling mechanism

lubricant
water is the major component of mucus, serous fluid, digestive fluids, saliva, etc.

Tissues / Types

= Tissue Types and their origins =

There are four principal types of tissue:
= Extracellular Materials =

Matrix - primarily important in connective tissues, it consists of a ground substance plus protein fibers. The ground substance is composed of complex molecules; can be a fluid, gel, or solid.
= Cell Junctions - points of contact between adjacent cells. The different kinds of junctions have distinct functional differences: = == Tight junctions (zonula occludens) - fluid-tight seals. Common in epithelial tissues, girdling the whole cell near the free surface. “stitches” adjacent cells together. Common anywhere a tight seal is needed,  often found in places were the control of passage of substances through membranes is important - molecules can’t leak around the cells, they must go right through them. Ex: digestive, bladder. ==

Communicating junctions
= Epithelial Tissues =

Covering & lining epithelium
==== the two criteria: how many layers (1 layer = simple; > 1 layer = stratified) and shape (squamous, cuboidal, columnar) of cells. for the stratified types, usually only the outer layers look like squamous or columnar cells; the underlying layers all look cuboidal. ====

=
pseudostratified ciliated columnar--appears multilayered, but all cells are in contact with basement membrane. Cells reaching free surface have cilia; functions similar to simple ciliated columnar tissue. lines most of respiratory tract =====

Exocrine glands secrete their products into ducts; their classification is based on how they secrete... is the product released by itself, or is part or all of the gland’s cells released also?

 * Holocrine glandsentire cell releasedsebaceous glands
 * Apocrine glandsapex of cell releasedmammary glands
 * Merocrine glandssubstance onlysalivary, digestive

Endocrine glands secrete their products (hormones) into the bloodstream through the extracellular fluid (pituitary, thyroid, etc.) We will deal with them in detail later.
= Connective Tissues =

Ground substance
Contains molecules that determine the ‘consistency’ (fluid, gel, solid) of the matrix. The most important are:


 * Hyaluronic acid - thick, slippery substance - lubricant, glue-like
 * Chondroitin sulfate - jellylike, provides support
 * Adhesion proteins - help to anchor cells

Fibers
Provide support, strength. Embedded in the ground substance between the cells of the connective tissue. 3 kinds:


 * Collagen fibers - very strong, resistant to stretching, but flexible; long single fibers made of collagen
 * Elastic fibers - smaller than collagen fibers, can be stretched without breaking, less strong than collagen fibers, flexible; single or branching, made with elastin & fibrillin
 * Reticular fibers - short, branching fibers, less strong than collagen, inelastic; used as support; made of collagen

Cells
Cells in connective tissue are most often named for the matrix they secrete. Cell names can end in -blast (cells actively secreting matrix), -cyte (cells metabolically maintaining matrix, but not forming new matrix), and sometimes -clast (cells breaking down matrix). Not all of these three kinds of cells will be found in a specific tissue.

Cell names start with the kind of matrix being made:

Fibro-cells making or maintaining fibrous CT (fibroblast, but no “fibrocytes”)

Chondro-cells making or maintaining cartilage (chondroblast, chondrocyte)

Osteo-cells making or maintaining or breaking down bone (osteoblast, osteocyte, osteoclast)

Blood tissue
= Muscle Tissue =

General features
Contains cells that respond to an electrical stimulus by contracting

Often interspersed with connective tissues, especially dense regular connective tissue

Smooth--Small, spindle-shaped, 1 nucleus, not striated, many gap junctions, involuntary
= Nervous Tissue =

General features
Contains cells that respond to an electrical stimulus by generating & conducting another electrical stimulus (neurons)

Also contains cells that act as physical & metabolic support for neurons

= Membranes = Epithelial layer + underlying CT makes an epithelial membrane. Mucous & serous membranes are the most common kinds within the body; cutaneous membrane (skin) lines the outside. In addition, synovial membranes have connective tissue but no epithelium.

Mucous
Line body cavities & surfaces that open to the exterior; lots of goblet cells, generally cuboidal or columnar cells over irregular CT; produces mucus (& many other secretions besides)

Serous
Line cavities that do not open to the exterior; generally simple squamous epithelium over areolar CT; produces serous fluid (watery, lubricating fluid)

Synovial
line joint cavities, tendon sheaths; areolar CT with additional elastic fibers and adipocytes; produce synovial fluid, slippery lubricating & nutrient fluid.

Integumentary System

= Skin =

Anatomy
Two layers, epidermis (stratified squamous epi.; ectoderm) and dermis (dense irregular CT; mesoderm) underlain by 3rd layer, hypodermis (loose CT); also called the subcutaneous fascia; area of fat storage. One of the larger organs of the body.

Epidermis
A strat. squam. epi. (keratinized); acts as hydrophobic protective barrieravascular30-50 cells thick; most layers are dead cellspalms, soles have 5 distinct layers — “thick” skin; found in hihg-friction areasother areas have 4 distinct layers — “thin” skin

Cell types:

keratinocytesmelanocytesothers

Epidermal layers: follow the course of an individual cell from start to finish

Stratum basale (str. germinativum)
a single layer of keratinocytes, which secrete the BM of epidermis and divide on a 17-20 day cycle. also found here are cell bodies of melanocytes. One keratinocyte daughter cell remains in S.B., while the other is pushed up into the:

Stratum spinosum
about 10 cells thick; keratinocytes start to flatten out, amount of keratin increases. some of these cells can still undergo mitosis. processes of melanocytes extend among the keratinocytes, k’s. pick up melanin from these. Next:

Stratum granulosum
2-5 cells thick, keratinocytes continue to flatten, granules of keratohyalin form; lipids released into gaps between cells; envelope of keratin proteins begins to form under cell membrane; organelles and nucleus begin to die & disintegrate

Str. lucidum (present in thick skin only)
2-3 cells thick

keratinocytes dead, no internal structure visible (except keratin fibers); appears transparent, hence name

Str. corneum
20+ layers thick; dead cells, heavily keratinized, held together by desmosomes. cells flat, scale-like; surrounded by lipids; as desmosomes break, cells are shed (desquamate) these cells are cornified = dead & full of keratin

total trip time = 2-4 weeks? 50 days?

Recapping thick vs. thin skin —

Thick:5 layers, many layers of S.C. palms fingertips, soles of feet, toespapillary layer of dermis forms curving, parallel ridges

Dermis
generally thicker than epidermis; many blood vessels, nerve fibers, glands, hair follicles present.

mainly dense irregular CT with elastic fibers also; adipocytes and immune components (mast cells and macrophages) present also.Dermal layers (deep  shallow)

Reticular layer
very fiber-rich; collagen fibers irregular, elastic fibers more regular;  skin stretches better in some directions than others - must be taken into account when making surgical incisions.

over-stretching causes striae “stretch marks”

this layer contains lymph vessels, adipocytes, bases of hair follicles

Papillary layer
contains projections (papillae) extending up towards epidermis - few fibers, more cells - many blood vessels which supply epidermis

bedsores (decubitus ulcers) demonstrate importance of good blood flow through dermis

Protection
physical barrier to microorganisms, physical traumasecretions retard pathogen growth (pH 4 - 6.8)retards UV penetration

=== Thermoregulationheat lost by dilating blood vessels, sweating,direct conduction of heatheat saved by constricting blood vessels, insulation of subcutaneous fat, shivering(brown fat in infants)(arrector pili muscles) ===

Absorption/Excretion
absorption limited to fat-soluble, hydrophobic compounds, small amounts of O2 & CO2 urea (ammonia excretion) in sweat, also excess salt

Synthesis
3 main ‘products’ of the skin:melanin, keratin, vitamin D (regulates metabolism, absorption of Ca+ and Phosphorus)

7-dehydroxycholesterol (in skin cells) + UV  vit. D3; (carried to liver)  25-hydroxycholecalciferol; (carried to kidneys)  calcitriol = most active form. so the skin is actually an endocrine gland.

Sensory reception
receptors detect heat, cold, pain, light touch, pressure;

hair follicles have receptors that detect hair movement

Fluid regulation
prevention of water loss across skin (dehydration in burn patients)

Blood reservoir
Dermal layers contain up to 10% of blood volume

Skin color
Skin color is determined by 3 pigments — melanin, carotene, hemoglobin (locations)

melanin production highly variable. UV exposure increases rate of synthesisalbinism = genetic inability to produce melanin - total lack of pigmentvitiligo = patchy melanin distribution - cause unknown, may be autoimmune against melanocytes

Other unusual colorations: jaundice, cyanosis, erythema (redness)

= Epidermal Derivatives =

Hair
functions? (UV and thermoregulation, sensation, protection of orifices, pheromonal?)Very high mitotic activity cellsHairs grow from follicles, epidermal evaginations into the dermis (why?)

Hair develops from dividing cells in matrix of bulbcolored by melanin, sometimes with iron and sulfur added. tyrosinase decreases with age,  loss of pigment.

hormonal effects - androgens

Nails
= Homeostasis =

Wound healing
Depending on depth- epidermal vs. deep

Epidermal wound healing
(abrasion, 1st or 2nd degree burn)

keratinocytes of the St. B. migrate inwards from the edges of the wound until they meet; contact inhibition prevents excess growth; keratinocytes then proliferate and reform layers.

Deep wound healing
involves CT, so is harder to heal, takes longer, more complex.inflammatory phase: blood pours into wound from broken vessels; clot forms, and seals the wound from the outside. blood vessels in the area dilate, become more permeable  redness, swelling, warmth; brings WBC’s and antibodies to area for immune function. mesenchyme (fibroblast) cells migrate in also.

migratory phase: clot  scab; epithelial cells migrate beneath scab to bridge wound; fibroblasts produce collagen fibers & matrix (granulation tissue); blood vessels begin to regrow.

proliferative phase: like migratory phase, but more of it.

maturation phase: as epidermis is restored to normal thickness, scab is lost as epithelial cells dequamate. repaired CT is often richer in fibers than normal tissue, often low in blood vessels. Overlying epi. often without hair, melanocytes.

Burns
anything that denatures proteins is a burn- heat, chemical, radiation, electricity. because they disrupt the StSE, they demonstrate how important it is.

1st-degree
epidermis only; redness, no blistering; skin functions remain

2nd-degree
full thickness of epidermis, and some (or most) dermis; redness, blistering, fluid accumulation; epidermal derivatives deep in the dermis usually not affected; healing takes place from edges and from intact epi. derivatives; several weeks to heal if protected from infection; because of dermal damage, may scar if enough dermis is involved.

3rd-degree
full thickness of skin, destroying epidermis, all derivatives, dermis and contents; color varies; edema, loss of sensation; healing can only occur from edges of burn; infection risk high, fluid loss great

= Aging = Effects are predictable: fibroblasts slow fiber production, so # of fibers and strength (& elasticity) reduced. Keratinocyte mitosis slows, hairs grow more slowly, glands produce less, melanin production tends to be reduced, healing ability lessened.

= Disorders =

Skin cancerBasal cell — St. basale - low chance of metastasis - most frequentSquamous cell — St. spinosum - greater chance of met., less frequentMelanoma — in melanocytes - high chance of met., rare
Skeletal System

= Functions of the skeletal system: =

Support of soft tissues:
attachment of muscles, tendons, and (indirectly) organs

Protection of organs:
most obvious examples - the brain surrounded by the cranium and base of skull, lungs, heart & major blood vessels surrounded by ribcage, vertebral canal

Motion
Provide something for muscles to work against

Homeostasis of Ca and P
Primary reservoirs of these elements, whose most important role is in nerve and muscle tissue function (not skeletal support)

Hemopoeisis
Bone marrow is the site of blood tissue formation, which means O2 and CO2 transport, and immune system components

Energy storage
Bone marrow is an important site of adipose tissue formation.

= Gross anatomy of bone = Major parts: (of a typical ‘long’ bone, like a femur or humerus)

Diaphysis
The main shaft of the bone

Epiphysis
The proximal and distal ends of the bone, generally flared out & flattened for articulation with other bones

Epiphyseal plate (or line)
The junction of the epiphyses with the diaphysis. During active growth, this region is not bone tissue at all - it is hyaline cartilage

Articular cartilage
A thin layer of hyaline cartilage that covers the epiphyses where they articulate with other bones.

Periosteum
A two-layered membrane that covers the bone (except at the articular cartilages). The outer layer is dense irregular CT; the inner layer is elastic CT with many bone cells.

Medullary / marrow cavity
The cavity that is found within the diaphysis of long bones, where some of the marrow is found - this is not present in many bones.

Endosteum
a thin membrane composed mainly of bone-producing and bone-removing cells.

= Microscopic anatomy of bone = Bone is a connective tissue, so it has matrix surrounding cells. Matrix is 25% H2O, 25% collagen fibers, 50% mineral salts.

A. Cells are of four types:

Osteoprogenitor cells
unspecialized, can divide repeatedly; found mostly in the periosteum and endosteum

Osteoblasts
form from osteoprogenitor cells; actively form bone, no longer can divide

Osteocytes
mature osteoblasts; no secretion of matrix, but still metabolically active

Osteoclasts
derived from immune cells; secrete acids & enzymes that help break down bone

Matrix:
calcium phosphate + calcium carbonate, mostly; crystallization of these salts along matrix fibers = calcification.

fibers - tensile strength, flexibilityCaPO - compressive strength, hardness

= Bone formation and growth =

Hyaline cartilage forms model of bone; surrounded by perichondrium
==== Cartilage model grows interstitially and appositionally; chondrocytes in mid-region hypertrophy, burst, release acids, trigger calcification - chondrocytes die from lack of nutrient diffusion. (calcified cartilage)Nutrient artery penetrates mid region, carrying osteoprogenitor cells with it - starts formation of 1 ossification centerBone collar forms under perichondrium of midregion. ====

At 1 o. c., osteoblasts lay matrix over calcified cartilage, forming spongy bone. Close behind, the osteoclasts break down the matrix, leaving a cavity, which fills with red marrow.
==== Epiphyseal arteries enter the ends of the bone, and induce the development of 2 o.c.’s there. No medullary cavities form, and cartilage replacement is never quite complete (it remains on articular surfaces). ====

Growth
Bones grow either by appositional growth, which can add to their girth, or by cartilage replacement at epiphyseal plates. The plate has 4 regions:

(epiphysis)

zone of calcified cartilage
(diaphysis)

Eventually, osteoblast growth overtakes chondrocyte growth, and lengthening stops.

= Bone homeostasis =

Remodelling:
Despite appearances, bone is continually remodelling itself; osteoblasts and osteoclasts continually make and break bone.Several factors alter the rate at which o.b.’s and o.c.’s work:

Mechanical stress (compression  more matrix; tension  more fibers)
Effects of weight-bearing activities- lack of same (1% loss/week)

fracture hematoma--blood clot, within periosteum; swelling, inflammation. forms framework for repair
=== procallus--capillaries invade, fibroblasts start forming granulation tissue. mass called procallus. fibroblasts lay down collagen fibers, osteoprogenitor cells turn into chondroblasts and form fibrocartilage at the procallus (soft callus) ===

Aging
2 main effects: loss of calcium, largely due to reduced sex hormone production; and reduced protein synthesis, leading to increased brittleness.

One of the most common conditions caused by aging is osteoporosis — extremely thin and brittle bones caused by reduced osteoblast function. It is most common in women- bones are usually smaller to begin with, so loss is more damaging; menopause greatly reduces the production of estrogens, so osteoblast activity slows. Very low body fat content can also cause osteoporosis (men & women) because the presence of adipose tissue stimulates sex hormone production - very low-fat diets, or inadequate total calories in the diet can also cause it.

Osteoarthritis is the result of breakdown of the articular cartilages. Once bone tissue is exposed, the bone attempts to “fix” itself by reacting as though a fracture has occurred, and the joint can become fused.

Calcium regulation:
ca++ required for: muscle contraction, nerve conduction, enzymes, blood clotting

= Components of the skeleton- =

Long
The ‘typical’ bone - has a diaphysis of compact bone, epiphyses of spongy bone, and a medullary cavity; forms endochondrally

Flat
Bones without medullary cavities - spongy bone all the way through. Can form endochondrally or intramembranously

Unusual
Bones that may or may not be present. The two most common types are:

wormian bones - flat bones that form from additional centers of ossification in the skull. most common in the lambdoidal suture.
==== sesamoid bones - ‘seed-shaped’ bones that form as reinforcements within tendons. The two sesamoids that everyone has are the patellae (kneecaps). Others form as a result of long-term stress on a tendon where it passes over an articulation, especially in the metacarpals and phalanges of the hands and feet. ====

Skull
Housing for brain, special sensory organs; entryway for respiratory and digestive systems. To help reduce the weight of this large mass of bone, the bones of the facial region contain air-filled sinuses-

Paranasal
sinuses in the maxillary, frontal, ethmoid, and sphenoid bones; also act as ‘resonating chambers’ for vocal cords. Lined with mucous membrane, draining into nasal cavity.

Mastoid
located in mastoid process of temporal bone - weight reduction

Vertebral column
Divisions -

Curves-

4 in adults:

cervicalposteriorsecondarythoracicanteriorprimarylumbarposteriorsecondarysacralanteriorprimary

1 in fetus, anterior

abnormal curves-

scoliosis - lateral bendkyphosis - exaggerated thoracic curve

vertebrae separated by disks-

annulus fibrosus - fibrocartilage, very strong & flexiblenucleus pulposus - elastic connective tissue, very elastic

Appendicular Skeleton - selected comments
The limb girdles demonstrate a compromise between strength and flexibility (in other words, the more flexible a joint, the weaker it is).

— pectoral girdle weakly attached to body, glenoid oriented laterally, designed for tensile forces, arboreality

— pelvic girdle strongly attached, less mobility, greater weight concerns -supporting viscera, and weight of the body on legs

differences resulting from sex hormone influences:bipedalism & childbirth

angle of leg bones - keeping weight centered

Articulations

= Introduction = articulation (joint) = point of contact between two or more bones, between cartilage and bone, or between teeth and bone.

The anatomy of a joint determines its function; the range of motion it can produce, the amount of support it provides.

= Classification =

Functional classification — degree of motion-
= Types of joints (by functional classification) =

All diarthroses are synovial joints, and are bounded by articular cartilage and articular capsule.
The capsule surrounds the cavity and unites the articulated bones. There is an outer fibrous capsule which unites with external ligaments and a synovial membrane.

There are often other accessory structures - ligaments, bursae, articular discs (menisci); ‘torn cartilages’ are damaged articular discs

How strong/mobile is a joint?
Determined by: shape of bones, strength of ligaments, muscle tension, hormonal influences

Types of movement:
Flexion/extension (hyperextension)

Rotation/ circumduction

adduction/abduction

Types of diarthroses:
gliding/arthrodial {side-to-side}[carpals, tarsals]

hinge/ ginglymus {flexion/extension}[elbow]

pivot/trochoid {rotation}[atlas-axis]

ellipsoidal/condyloid {fl.-ex.; ad.-ab.}[carpals-radius]

saddle/sellaris [trapezium-1st metacarpal]

ball-and-socket/spheroid

Special movements:
elevation/depression

protraction/retraction

inversion/ eversion

dorsiflexion/plantar flexion

supination/pronation

= Disorders: =

Shoulders & Knees
dislocations of shoulder - rotator cuff injury

the shoulder joint consists of:

articular capsuleglenoid labrumcoracohumeral ligament, glenohumeral ligamentstendons of infraspinatus, supraspinatus, teres minor, subscapularis muscles

the knee consists of:

articular capsuleextracapsular ligaments:patellar, medial & lateral patellar retinacula, medial & lateral collaterals, poplitealsinfracapsular ligaments:anterior & posterior cruciate articular discs (menisci) {attached by transverse & coronary ligaments}

Arthritis & gout
Muscles

= Types of Muscle Tissue =

Smooth muscle
= Functions of Muscle Tissue =

Thermogenesis
= Characteristics of M. T. =

elasticity
= Anatomy / Innervation of MT =

Nerve and blood supply
why are nerves and blood so important to muscles?(irritability/nutrients/O2/wastes)

fibers are full of myofibrils (striated): these are the contractile elements
==== myofilaments:myofibrils contain tiny threadlike structures, myofilaments.these are characterized as thick or thin. The filaments overlap.in a relaxed muscle, little overlap; in a contracted muscle, much overlap. ====

=
the thin filaments of actin, troponin, tropomyosin; main chain is twisted strand of actin molecules, with myosin-binding sites pointed outwards. troponin-tropomyosin cover the outside of the thin filament, and control whether myosin and actin can contract.this is why we say that actin and myosin are contractile; troponin and tropomyosin are regulatory. =====

a 3rd kind of filament, elastic filaments, seems to help stabilize thick filaments.
==== sarcomeres:myofibrils are made up of a series of repeating units, sarcomeres. each contains a series of light and dark regions. at each end is a Z-line (or disk). the light & dark effect (& therefore the striated bit) is the result of greater or lesser overlap of myofilaments. ==== === The sarcoplasmic reticulum:The endoplasmic reticulum of other cells becomes the sarcoplasmic reticulum in muscle cells. The SR is more organized and regular than ER. SR encircles each myofibril. SR forms sacs called terminal cisterns which encircle a myofibril. SR is normally full of a Ca++ solution. Between each terminal cistern is a transverse tubule, a tube that wraps around the myofibrils and also communicates with the outside of the cell; its full of extracellular fluid. === = Muscle movement: microscopic = Muscles don’t accordion-pleat, they slide.

Contraction: The sliding filament model
The thin filaments in the sarcomere are pulled toward each other, along the thick filaments. The filaments do not change in length. What causes the pull?

Calcium’s role
In a relaxed muscle, Ca++concentration is low; pumps actively transport Ca++ out of sarcoplasm into the SR. When a muscle cell gets the message from a neuron, special channels open, flooding Ca++ into the sarcoplasm around the filaments. Ca++ binds to troponin, changing that molecule’s shape-- this bends troponin-tropomyosin away from the myosin-binding sites on actin.

ATP’s role
In relaxed muscle, myosin is in an energized state. ATP attaches to myosin heads - myosin splits ATP to ADP + P, & uses the energy to “cock” itself, in preparation for muscle contraction. This activated myosin spontaneously binds to actin if the binding sites are available. Otherwise, it just sits, waiting. Once binding sites become available on actin, several steps happen in rapid succession:

the ATP is split, the myosin head recocks, and the myosin head rebinds to actin (if available).
As long as Ca++ and ATP levels are high, this cycle repeats.

Relaxation
Once the signal to contract ceases, the Ca++ gates close, and Ca++ pumps rapidly remove Ca++ from the sarcoplasm; so thin filament binding sites covered.

Motor Units:
Muscle cells/fibers are innervated by motor neurons. A single motor neuron will innervate multiple muscle cells. The number of muscle cells / neuron is an indication of how fine the muscular control over a structure is; the fewer fibers/neuron, the greater the control. Range:2 - 2000 fibers/neuron, mean 150 (fingers, lips vs. rectus fem.)

Neuromuscular Junctions
=== Synapsesa tiny gap between two irritable cells, across which a signal can jump under the right circumstances. usually you think of these between neurons, but muscle fibers get stimulated the same way. ===

Parts:
==== axon terminals(quick review: a nerve cell is a neuron; each neuron has a long, cable-like axon extending from it) at the end of each motor neuron axon, the axon branches into axon terminals. at the tip of each terminal is a synaptic end bulb. within the bulb are synaptic vesicles (phospholipid membrane-lined packages) packed with neurotransmitters ====

motor end platesthe sarcolemma below the axon terminal is specialized as the motor end plate. it is studded with neurotransmitter receptors, 30 - 40 million of them
==== neurotransmitters (acetylcholine, in this case)transmit the (basically) electrical nervous impulse across the synapse as a chemical signal. the neurotransmitter permits the nervous signal to excite the motor unit. ====

How it works:
As a nervous impulse (much, much more on that later) reaches the axon terminals, it causes the symaptic vesicles to release their neurotransmitters into the synaptic cleft. The acetylcholine is picked up by the receptors on the end plate, and this triggers opening of Na+ channels in the sarcolemma at the motor end plate. The flood of Na+ into the muscle cell causes a change in electric voltage across the sarcolemma (because this is a big flow of + ions). This voltage change is “contagious”; it spreads along the muscle cell from the point of stimulation. (Most neuromuscular junctions are located near the midpoint of a muscle cell’s length).The voltage change travels down into the transverse tubules (T-tubules; remember them?). This voltage change in the T-tubules induces Ca++ channels in the adjacent terminal cisterns of the sarcoplasmic reticulum (SR) to open. Ca++ floods into the sarcoplasm, and the muscle contracts.

What if it doesn’t work?
If no nervous signal crosses the neuromuscular junction, then obviously no contraction can take place; myasthenia gravis is an example - autoimmune disease, antibodies block ACh receptors on motor end plate, progressively reducing ability of ACh to stimulate muscle cell. MG tends to affect muscles of face & neck; may progress to limbs, respiratory muscles (usually not). How to treat? — increase levels of ACh by reducing AChE (acetylcholinesterase inhibitors), reduce antibody levels with steroids. (other treatments exist).

If Na+ channels don’t close, then the electrical signal never stops, Ca++ continually floods into the cell, muscles continue contraction as long as ATP present (tetany); can be caused by; repeated nervous stimulation, outside electrical stimulation, bacterial toxins (tetanus), neurotoxins (nerve gas - AChE inhibitor).

Muscle Tone
Random, asynchronous firing of motor units; if lacking, hypotonia; if increased, then hypertonia (spasticity or rigidity)

Phosphagen system — creatine phosphate (found only in muscle cells) gives up phosphate group to synthesize ATP (CP + ADP  C + ATP) 15 sec. worth in cellanaerobic
=== Glycogen-lactic acid — 30 -40 sec. worth in cell. breakdown of glycogen in muscle cells to form glucose; breakdown of glucose (also from bloodstream) to form pyruvic acid (then to lactic acid). 2 ATP / glucose. lactic acid mostly diffused to blood; some cells (cardiac) can oxidize LA to make more ATP.anaerobic === === Aerobic — after 40 sec. slower than glycolysis, but efficient;  36 ATP / glucose. glucose comes from usual sources (glycogen, bloodstream) and O2 comes from blood and myoglobin. As long as the bloodstream supplies sufficient O2 and glucose, ATP is generated.aerobic === = Muscle tension =

Twitch:
A single contraction of a motor unit in response to a single neuron action potential. (remember, it’s all-or-none)

latent period -(Ca++ release - 2 msec)contraction - 10 -100 msecrelaxation -(Ca++ back to SR - 10 - 100 milliseconds) after stimulation, a refractory period (5 - 300 msec; skeletal - cardiac) occurs.

The refractory period is caused by the inability of a new AP to initiate.

Multiple motor unit summation / recruitment
increase in # of MU’s firing; helps to control force of muscle contractions

Tetany
20-30 stim/sec — incomplete (partial relaxation)80 + — complete (no relaxation at all)

Treppe - staircase effect
stims too far apart for summation will cause increasing contractions, to threshold. same explanation as others? (buildup of Ca++ )

Types of muscle contraction
(Most movements are a combination of all of these)

Isotonic — constant load:
concentric - muscle shorteningeccentric - muscle lengthening (more likely to cause soreness?)

Isometric — constant length
= Fiber types = Most muscles in the body contain a mix of fibers; all fibers of a motor unit are identical. Different individuals may vary in their fiber makeup - leg muscles of sprinters tend to have lots of fast-twitch fibers (60%) while marathoners tend to have less (20%).

Slow twitch / slow oxidative / slow red
lots of myoglobin & mitochondria; ATP from aerobic; slow, steady ATP production; slow fatigue rate; little glycogen

fast glycolytic / fast white -- little myoglobin & mitochondria; ATP from glycolysis; quick fatigue; lots of glycogen
= Cardiac muscle =

Anatomy
cells are shorter, wider, and branched (compared to skeletal muscle); more mitochondria; usually only one nucleus. similar arrangement of sarcomeres; less SR. connected at ends to each other by intercalated disks- desmosomes & gap junctions. these allow muscle contractions to be spread from one cell to the next. also - some cardiac cells are autorythmic.

Physiology
almost exclusively aerobic; twitch is much longer than in skeletal muscle because channels that allow Ca+ to enter stay open longer. Na+gates prolong refractory period to about .3 seconds - this helps prevent summation and tetany.

= Smooth muscle = visceral smooth muscle - VSM - lots of gap junctions, contracts as unit; forms sheets of contracting tissuemultiunit smooth muscle - MSM - few gap junctions, few cells per neuron; rare, in eye, arrector pili, bronchioles

Anatomy
small, spindle-shaped; single nucleus; thick & thin filaments present, but not in sarcomeres; no T tubules, little SR

Physiology
Heart

= Heart Anatomy = located in mediastinum; 4 chambers; 2 atria, 2 ventricles; cone-shaped, with apex pointing down & left, base at top.

pericardium:
fibrous pericardium — dense irreg.; anchors heart to diaphragm (does not stretch -- tamponade = compression of heart by accumulated fluid)

serous pericardium — makes space around heart. outer parietal, inner visceral (aka epicardium) layers. fluid between them pericardial fluid.

myocardium:
bulk of heart muscle — made up of cardiac muscle cells. formed into spiral shape, more or less aligned along axis of heart; atrial & ventricular components independent.

endocardium:
endothelial lining of atria & ventricles. continuous with lining of blood vessels.

Chambers:
atria: thin walled upper chambers — flappy parts called auricles; ventricles: larger, thick-walled chambers separated by interventricular septum. connective tissues separate atria & ventricles. atria separated by interatrial septum, with fossa ovalis. surfaces of chambers ridged. thicknesses correlate with distance blood must be pumped.

Valves:
rt AV = tricuspid;l AV = mitral/bicuspid; flaps cusps; chordae tendineae connect to cusps and papillary muscles of ventricles. (prevent regurgitation)semilunar valves — 3 cusps; to arterial trunks

= Blood flow through the heart =

heart is really 2 pumps in one- r side deoxy, l oxy
3 circuits are involved; pulmonary, systemic, cardiac

= Conduction system = == About 1% of cardiac muscle cells are autorythmic - these are concentrated in the sinoatrial (SA) and atrioventricular (AV) nodes. They also form the cells of the conduction system. These cardiac muscle cells are specialized to behave more like neurons, transmitting action potentials from one place to another. == Besides the nodes, the conduction system is made of:

the AV bundle (bundle of His)the left & right bundle branchesthe purkinje fibers (conduction myofibers)

SA node cells have an autorythmic rate of about 90 beats/minute. This is faster than other autorythmic cardiac cells, so the SA node ‘sets the pace’ for the rest of the heart - that is, it is the natural pacemaker. The AV node cells contract autorythmically at about 50 beats/min., but the faster beats coming from the SA node ‘override’ that slower pace. The rest of the conducting fibers beat at about 30 beats/min.

The speed of the SA node can be varied by signals from the nervous and endocrine systems.

ventricles contract (from apex upwards to valves)
= Contraction physiology = == A big functional difference between cardiac muscle cells and skeletal muscle cells has to do with how long they remain depolarized following stimulation. Skeletal muscle cells repolarize fast; cardiac cells stay depolarized for a long time (.25 sec). A flow of Ca+ into the cells keeps them depolarized.A muscle cell can only contract while Ca+ is present - eventually Ca+ gets pumped out, and the cardiac cell relaxes.The cardiac refractory period is longer than the period of contraction (in skeletal muscle it is much shorter). == = Cardiac cycle = Everything that happens in the heart, from the end of one heartbeat to the end of the next, is referred to as one cardiac cycle. The basic idea is that both atria relax & contract together, and both ventricles relax & contract together, but the atria and ventricles are slightly out of phase.

Relaxation
all chambers relaxed. ventricular cells repolarize, ventricular pressure drops. pressure of blood in arterial system forces semilunar valves closed. when pressure drops enough (below blood pressure in atria [controlled by venous blood flowing into them]), the AV valves open and blood starts to fill the ventricles.

Ventricular filling
chambers still relaxed. blood flows into the ventricles from the atria; the SA node beats, depolarizing the atrial cells (P wave). atria contract, forcing additional blood into ventricles (about 130ml total EDV)

Ventricular contraction
atria contracted, ventricles relaxed; impulse from SA passes into AV node, then takes .1 seconds to travel to the AV bundle. Then ventricles start to contract, pushing up pressure in ventricles; AV valves close; isovolumetric contraction - pressure rises rapidly. when ventricular pressure exceeds aortic pressure (80mmHg) and pulmonary trunk pressure (20mmHg) semilunar valves open, forcing blood into aorta and pulmonary trunk. during all this, the atria relax. then, the ventricular cells begin repolarization (T) and relaxation, leaving some blood in the ventricles (about 60ml total ESV)

The whole cycle takes about 0.8 seconds, about half relaxation (diastole) and half contraction (systole). When the heart rate speeds up, systole remains constant - diastole gets shorter.

= Cardiac output = == Stroke volume(EDV-ESV; 70ml) x heart rate(75bpm) = cardiac output( 5.25 l/min). This is approximately the total volume of blood in the body. == Regulation of stroke volume:

Preload:
stretch on heart before contraction; the more cardiac muscle is stretched, the more it contracts — Frank-Starling law — duration of diastole and venous pressure determine preload- as rate increases, diastole is shorter, less preload; increase in venous pressure increases preloadF-S law helps to equalize output of both ventricles; a strong contraction in one ventricle will result in an increase of blood filling the other ventricle, which then contracts more strongly - out put of both sides stays equal

Contractility:
Strength of contraction for a given preload; can be increased by + inotropic agents (digitalis,epinephrine), decreased by - i. a. (acidosis, anoxia)

Afterload:
pressure that must be exceeded to expel blood from ventricle (20 mmHg pulmonary, 80 mmHg aortic [same as diastolic blood pressure]);

Congestive heart failure:

pumping becomes less effective, more blood remains in heart at end of systole - eventually, heart muscle becomes overstretched, contracts less forcefully; + feedback; left side = pulmonary edema; right side = peripheral edema

Feedback to brain:
proprioceptors, chemoreceptors, baroreceptors monitor peripheral activity & report to brain; also, input from other parts of the brain (sensory and limbic stimulus);

Output to heart:
cardiovascular center in medulla sends signals via cardiac accelerator & vagus nerves:

Cardiac accelerator nerves: sympathetic division of nervous system - nerve endings release norepinephrine onto heart muscle; increase heart rate, strength of contraction

Vagus nerves: - parasympathetic division of NS - nerve endings release acetylcholine; decrease heart rate (but don’t affect strength of contraction much)

Hormonal control
Epinephrine & norepinephrine from the adrenal glands have the same effect as the cardiac accelerator nerves; thyroid hormones also elevate heart rate and strength of contraction.

= Developmental details = During early development, the atria and ventricles are not divided in two. Septa develop and separate the chambers about the 8th week. A small opening - the foramen ovale - remains, connecting the atria. This normally closes at birth, leaving a depression, the fossa ovalis.

Hemodynamics

= Anatomy of Blood Vessels =

Arteries - carry blood away from the heart to tissues
Parts-tunica interna (endothelium, basement membrane, elastic lamina)

tunica media (elastic fibers, sm. muscle) (contractility, elasticity)

tunica externa (elastic & collagen fibers)

Anastomoses
Arteries may branch together, or with veins directly = alternate routes of flow

Arteries that don’t - end arteries; occlusion = necrosis

Arterioles
Tiny — tunics become thinner & thinner - smooth muscle (t.m.) helps to regulate flow to capillaries

Capillaries
Excxhange = endothelium + basement membrane; no t. m. or t. e.

flow regulated by precapillary sphincters

Continuous — the usual (brain = held together by tight junctions)

Fenestrated — pores in endothelium - where diffusion of small particles/ions important

Sinusoids — incomplete, wide, gappy

Venules
tunica interna + tunica externa

Veins
three layers again - little muscle, mostly elastic CT; often contain valves to ensure proper flow

Sinuses — wide veins without muscle to control diameter (eg; sinuses in brain, coronary sinus)

Veins act as reservoirs of blood; 60% of total; important for diversion to other organs, or in case of hemorrhage

= Physiology of Circulation =

Velocity of flow — total trip time: approx. 1 min.
rate of flow inverse of cross-sectional area (4cm2 / 40cm/sec : 5000cm2 / 0.1cm/sec : 14cm2 / 15cm/sec)

Volume of flow
5.25 l/min: Cardiac output = stroke vol. X heart rate. but in addition,

pressure diffs. and resistance affect flow. CO = MABP/R.

Blood Pressure=generated by ventrcular contraction, volume of blood

Resistance increases as blood travels through smaller & smaller vessels - greatest in arterioles. Resistance depends on 3 things;

viscosity (cells [or proteins]/ volume)

blood vessel length

blood vessel diameter — 1/r4

SVR Systemic Vascular Resistance = all resistance offered by systemic vessels — since most resistance is in arterioles, major function is to control SVR

Capillary exchange
5% of blood, but all of exchange, in capillaries. 3 methods:

Bulk Flow — movement of fluids because of pressure diffs.
At arterial end of caps.: net flow out of blood (filtration)10 mmHg

at venous end: net flow back in (reabsorption)9mmHg

1 mmHg lost, retrieved by lymphatic system

Edema — increase in IF — caused by:

Venous return
pressure in rt. atrium about 0mmHg, allowing easy flow from veins; if rt AV valve is blocked, then things back up

skeletal muscle pump

repiratory pump

= Control of flow and pressure = The body has three mechanisms by which it can regulate blood pressure:

Cardiovascular center — regulates heart rate, contraction, vessel diameter - rate of flow and patterns of flow
input from cortex, limbic system, hypothalamus (non-feedback)

input from baroreceptors in carotid sinus, aorta via CN IX (feedback)

input from proprioceptors, chemoreceptors (feedback)

out put is via autonomic NS; ennervation to SA, AV, and myocardium

output to vagus = decrease heart rate & forceoutput to cardiac accelerator = increase heart rate & forceoutput to blood vessels = dilate/constrict vessels

Neural Regulation of Blood Pressure
carotid sinus reflex-(pressure to brain) baroreceptors stim. by stretch  decreased rate, dilation

aortic reflex - (systemic pressure) baroreceptors stim. by stretch  decreased rate, dilation

atrial reflex - (venous pressure) baroreceptors in rt. atrium: stretch  increased rate, force

chemoreceptors monitor CO2, O2, H+ ; if too little ox. or too much others, sympathetic response

Renin- Angiotensin- Aldosterone:
if volume or flow , kidneys release renin {converts angiotensinogen to} angiotensin {converted in lungs to angiotensin II, which} 1)vasoconstricts, 2)stimulates aldosterone secretion (increases Na+ and H2O retention)

Epinephrine - Norepinephrine
if volume or flow , these increase rate & force, vasoconstrict viscera, dilate cardiac & skeletal musc.

Antidiuretic hormone (ADH)
Strong vasoconstrictor - response to hemorrhage

Atrial natriuretic peptide (ANP)
if venous pressure high, vasodilation

Parathyroid hormone (PTH) & calcitriol
PTH - vasodilator; calcitriol - vasoconstrictor

Autoregulation
vasodilation or vasoconstriction, depending - most often triggered by O2 levels in tissues

= Shock & Homeostasis = inadequate cardiac output, such that O2 delivery is affected.

Causes:
hypovolemia — loss of plasma (burns, dehydration, diarrhea, kidney disease) or whole blood (hemorrhage)

loss of vasomotor tone — brain damage to medulla, ‘fainting’ (syncope)

Stage I/Compensated/non-progressive shock
negative feedbacks attempt to reverse drop in cardiac output - effective if blood loss not more than 15% of total.

Stage II/Decompensated/Progessive shock
above 15% volume loss, feedback mechanisms inadequate. Harmful positive feedbacks now start to appear. Stage II is reversible if caught in time.

Stage III/irreversible shock
if stage II conditions are not reversed, damage to heart, CNS, liver, kidneys, & the rest becomes fatal.

= Circulatory routes = Systemic; cardiac; pumonary; hepatic portal; fetal

Blood

= Blood Functions - = Transport — of gases, nutrients, waste products

Regulation of body systems — by hormone transport, pH regulationProtection — immune components

Blood trivia -

volume: 5 - 6 liters (male) 4 - 5 liters (female)about 7.5% of total body weightpH range of 7.35 - 7.45temperature about 38 C (100.4 F)

= Components of blood: =

= Hemopoiesis (hematopoiesis) = Blood cell formation takes place in red bone marrow.

Some cells in marrow are hemopoietic stem cells, or hemocytoblasts

these give rise to all blood cells.

These cells then divide and produce 5 other kinds of cells:

= Red blood cells = anucleate, lack cellular machinery, produce what little ATP they need anaerobically; oxygen-carrying, stuffed w/ hemoglobin (33% of weight); 5.4 mill/mm3 (males), 4.8 million/mm3 (females) turnover of 2 million per second.

hemoglobin ‘carries’ oxygen, releasing it in tissues where concentrations are low. O2 -carrying part called the heme group ; rest is globin protein. hemoglobin also helps transport CO2 - about 1/4 of CO2 is picked up by the globin portion.

Production
a.k.a. erythropoiesis — controlled by kidney cells- response to low O2 (erythropoietin)

erythropoietin stimulates reticulocyte production; reticulocytes mature into erythrocytes in 1 - 2 days. complete procedure takes  4 days.

Destruction
lacking repair mechanisms, RBC’s wear out in about 110 - 120 days. Macrophages in the liver, spleen, lymph nodes, & red marrow phagocytize the RBC, splitting & releasing heme + globin. heme is split: Fe3+ is transported back to bone marrow, non- Fe3+ portion metabolized: biliverdin  bilirubin  yellow, brown pigments released in urine & feces. globin broken down to amino acids, reused.

hematocrit — % RBC’s in blood -fem 38 - 46%; mal 40 - 54% anemia, polycythemia
= White blood cells =

function - attack pathogens, dead cells, foreign cells, sick cells
granulocytes + monocytes — non-specific cellular response; neutrophils 1st, macrophages 2nd, eosinophils 3rd

Types:
Granulocytes — ‘granular’ under microscope. all are mobile, usually leave blood vessels after transport to inflamed area

myeloblasts form promyelocytes, then differentiate into either:

basophils — promote inflammation, slow clotting
Agranulocytes — less distinct in staining; a mixed bag.

Monocytes — monoblast  monocyte  {leave blood}  macrophage
some fixed, some wandering; phagocytotic

Lymphocytes — lymphoblast  lymphocyte (T or B cells, NK cells)
B cells make antibodies; T cells kill other cells -or- coordinate lymphocyte response (more on that later)

Platelets — cell fragments, not whole cells.
megakaryoblast  megakaryocyte  metamegakaryocyte  breaks into fragments

WBC counts- useful in determining what is going on:
= Hemostasis = stopping blood loss. must be quick, local to region of damage. 3 mechanisms:

Spasm
immediate, strong contraction of smooth muscle in vessel walls near damage - reduces blood flow through damaged vessel

Platelets
adhesion (platelets stick to tissues underlying ruptured endothelium; platelets become activated, then) release (of the chemicals within platelets; these cause further activation, local vasoconstriction, and make the platelets sticky) aggregation (platelets stick together, blocking rupture)

Coagulation
blood is a very reactive liquid - if disturbed, it tends to solidify & form clots.

complex cascade reaction; once blood comes into contact with certain (most) substances, coag. is initiated — results in deposition of insoluble protein fibers

prothrombinase {converts} prothrombin {into} thrombin {converts} fibrinogen {into} fibrin {inhibits thrombin}

lack of certain factors results in hemophilia

after clot formation, it retracts, pulling edges of vessel together  eventually, clot is dissoved (fibrinolysis) by enzymes incorporated into the clot

= Blood typing = surfaces of RBC’s contain a variety of molecules that act as antigens: something that the immune system can make antibodies against. ABO system best known, other kinds of antigens exist as well.

Rh factor:

RBC with the antigen are Rh+, those without are Rh- plasma does not contain anti-Rh antibodies unless there is sensitization

hemolytic disease newborn (HDN) - Rh- mother carries Rh+ fetus - fetal blood leaks to maternal, mother makes antibodies. if further fetuses are Rh+, maternal antibodies can attack fetal blood cells

= Disorders: = anemia - iron deficiency, pernicious, hemorrhagic, hemolytic, sickle-cell, thalassemia

polycythemia, leukemia

Lymphatic System

= Lymphatic system = An ‘accessory’ circulatory system, consisting of closed-ended tubules, carrying lymph (basically just interstitial fluid) from the body tissues to the cardiovascular system. Functions:


 * Draining excess interstitial fluid
 * Transport of dietary lipids
 * Protection against pathogens

Formation and flow of lymph
blood plasma seeps/gets squeezed out of capillary walls, becomes interstitial fluid. bulk flow pushes this into the lymphatics. the walls of lymphatics are effectively 1-way valves, keeping lymph from backflowing into tissues.

lymph movement similar to venous flow - dependent on actions of skeletal muscles, helped by valves. lymph pushed from abdomen to thorax.

Lymph capillaries (lymphatics)
lymphatics are found just about everywhere, except - CNS, bone marrow, avascular tissues. anchoring filaments help hold lymphatics in place among tissue cells.

Special types:each villus of the intestines has a single lymphatic (lacteal) running down its axis. These pick up lipids from digested food and carry it to the bloodstream (milky  ‘lacteal’)

lymph capillaries converge to become vessels, which enter groups of lymph nodes. leaving the nodes, the vessels converge to become lymphatic trunks; these converge into 2-

Lymph ducts
thoracic duct - starts at cisterna chyli, runs superiorly and eventually drains into the left subclavian vein. drains most of body

right lymphatic duct - much smaller, collects lymph from rt. side of body superior to diaphragm

Lymph nodes
1mm to 1 in. in diameter - scattered throughout the body, but concentrated in the groin, axillae, viscera, neck. act as ‘filtering’ sites for lymph - screen out pathogens/foreign cells.

Anatomy
outer capsule (DICT) extends supporting trabeculae into center; lots of reticular tissue internally. internal cells organized as cortex (containing follicles, regions of packed lymphocytes [T-cells, B-cells] & macrophages) and medulla (lymphocytes & macrophages arranged as cords); sinuses allow flow of lymph through the node.

Function
lymph flows through in 1 direction only. as it does, the reticular fibers act to filter out objects present in lymph. if foreigh / pathogenic, lymphocytes & macropahges take care of them. also, the presence of these objects in the node can cause T & B cells to set off immune responses throughout the body (antibodies, ex.)

Lymph nodules
not surrounded by capsule, generally small, scattered through mucous membranes (mucosa-associated lymphoid tissue - MALT) occasionally these form aggregations - tonsils, peyer’s patches

Thymus gland
site of most T-cell production (hence name) - mainly important as a childhood organ, atrophies after puberty.  much T-cell maturation takes place early in life

Spleen
aside from its role breaking down RBC’s, spleen also is a site of B-cell proliferation- some macrophages (& phagocytosis) occur there also