Cells are the basic units of an organism. Cells form tissues, tissues form organs and organs form organ systems. All systems work together in coordination to keep the body in a homeostatic condition. This chapter covers the human digestive, excretory and reproductive systems.
1. Organ Systems
Organ and organ systems appeared first in the Phylum Platyhelminthes and continue till mammals. Two or more organs form an organ system with a common function. Division of labour is found among the organ systems.
| Organ System | Organs | Function |
|---|---|---|
| Integumentary | Skin and skin glands | Protection, excretion |
| Skeletal | Skull, vertebral column, sternum, girdles, limbs | Support, shape and form |
| Nervous | Brain, spinal cord, nerves | Conduction of nerve impulse |
| Circulatory | Heart, blood, blood vessels | Transport of gases, nutrients, wastes |
| Excretory | Kidneys, ureters, urinary bladder, urethra | Elimination of nitrogenous wastes |
| Reproductive | Testes and ovary | Gamete formation, secondary sexual characters |
| Endocrine | Pituitary, thyroid, adrenals, pancreas, etc. | Co-ordinates all organ systems |