Anatomy

The human body consists of innumerable cells. These cells are the basic units of the body. Cells of a common origin and the same function, make up tissues, particular types of tissue perform specific functions for life. The understanding of cellular structure and function is very fundamental for the study of Anatomy.

The cell is the smallest structural and functional unit of the human body. A cell has two parts, the cell membrane and the protoplasm. The protoplasm is surrounded by the cell membrane. The protoplasm is again divided into two parts. The more dense central part is called the nucleus. The outer part is called cytoplasm. The nucleus is the most important part of the cell.

Is an elastic membrane that limits the protoplasmic contents of cells? It also separates one cell from another. Its chemical composition is lipid protein and a small amount of carbohydrate.

Function of Cell Membrane

i. 	To maintain the shape of a cell ii. To control the passage of substance into or out of the cell.

Protoplasm: It is the living material inside the cell. It is semi fluid in consistency. In the centre of the protoplasm, there is the nucleus and surrounding that is the cytoplasm.

Cytoplasm: Cytoplasm consists of water (75%), organic substances and inorganic substances. Inside the cytoplasm, there are highly specialized living bodies, called organelles. The organelles may be membranous and non-membranous.

Membranous organelles	Non-membranous Organelles i.	Mitochondria ii. Endoplasmic reticulum iii. Golgi complex iv. Lysosomes	i. Ribosomes ii. Centrosomes iii. Microtubules iv. Microfilaments

Mitochondria

An external and internal membrane bound mitochondria; the internal membrane is folded inside. This inside folding is called christae. The space inside the mitochondria contains chemical substance known as matrix.

Function: This is the chief source of energy of the cell. It is also called the powerhouse of cell.

Endoplasmic Reticulum: It is a system of inters communicating channels in the form of vesicle and tubules. It is of two type -

i. 	Smooth endoplasmic reticulum ii. Rough endoplasmic reticulum.

Rough endoplasmic reticulum has ribosomes on its external surface and smooth one has none.

Function

i. 	Protein synthesis ii. Transmission of exportable protein.

Golgi complex: A membranous structure near the nucleus of almost all cells. It contains curved parallel series of flattenred saccules. It has got three parts cisternae, small vesicles and large vaculoes.

Functions

i.	The "packaging house" of the cell. ii. Synthesis of lysosome.

Lysosomes: They are membrane-bound small round structures. They contain enzymes necessary for digestion of ingested microorganisms.

Function: Digestion of foreign materials and unwanted organelles.

Ribosomes: They are roughly spherical structures. They may be free in the cytoplasm or attached to the rough endoplasmic reticulum. They consist of RNA and protein.

Function: Protein synthesis.

Centrosomes: These are a special zone of the cytoplasm, which contain two sharply staining granules called centrioles.

Function: Help in the process of mitotic cell division.

Microtubules: They are hollow cylindrical unbranched structure.

Function

i.	They help in maintaining the shape of the cell. ii. They form the structural basis for other cytoplasmic organelles like centrioles, flagella and cilia.

Microfilaments: These are thin threads like structure. They are present throughout the cytoplasm of all cells.

Function i.	They provide a cytoskeleton structural framework of the cell. ii. They participate in muscular contraction.