Human Physiology: Cells, Tissues and Organ Systems
Human Physiology: Cells, Tissues and Organ Systems asks you to connect structure to function, from organelles to organ systems. The exam tests definitions, tissue identification, organ-system matching and simple homeostatic reasoning rather than advanced biochemistry.
Cells
The human cell has a cell membrane, cytoplasm and nucleus. Mitochondria release energy by aerobic respiration; ribosomes make proteins; rough endoplasmic reticulum transports proteins; smooth ER makes lipids; Golgi packages secretions; lysosomes digest waste. Human cells lack a cell wall and chloroplasts. Chromosomes in the nucleus carry genes.
Tissues
- Epithelial tissue covers and lines; squamous is flat (alveoli), ciliated columnar lines the trachea, and glandular epithelium secretes.
- Connective tissue binds and supports: bone, cartilage, blood, tendon and adipose.
- Muscle tissue contracts: skeletal (voluntary, striated), smooth (involuntary, organs) and cardiac (involuntary, heart).
- Nervous tissue conducts impulses; neurons and neuroglia.
Organ systems and homeostasis
Organs cooperate in systems: digestive, respiratory, circulatory, excretory, nervous, endocrine, skeletal, muscular and reproductive. Homeostasis keeps internal conditions stable - for example, sweating cools the body and insulin lowers blood glucose.
Worked example
Question: Which tissue lines the trachea and why is it suited? Reasoning: the trachea must trap dust and move mucus upward; ciliated columnar epithelium has cilia and mucus-secreting cells, so it is the answer. Simple squamous epithelium would suit gas exchange in alveoli, not dust clearance.
Traps
Do not say human cells have a cell wall; blood is connective tissue, not epithelial; cilia move mucus while villi increase absorption; skeletal muscle is striated and voluntary.