Comprehensive Review of Human Anatomy and Physiology

Anatomy vs. Physiology

• Anatomy focuses on physical elements and their spatial relationships within the body.

• Physiology explores the mechanisms and processes that sustain life.

Gastrointestinal System

• Digestion: The process of breaking down nutrients into small, soluble molecules that can be absorbed into the blood.
    - Mechanical Digestion: Breaking food into smaller pieces.
    - Chemical Digestion: Breaking nutrients into small molecules.
      - The process by which chemical digestion occurs is called hydrolysis: splitting molecules by adding water.
      - Chemical digestion is sped up by the action of digestive enzymes (hydrolases).

• Humans have a complex digestive system structured as a tube called the alimentary canal which extends from the mouth to the anus.
    - Organized into specialized regions for specific phases: mechanical digestion, chemical digestion, and absorption.
    - Accessory organs include the liver, gallbladder, and pancreas.

Digestion Process

1. Mouth: Food enters and is chewed (mechanical digestion), increasing surface area for easier swallowing and digestion.
      - Salivary glands release saliva containing the enzyme amylase, which breaks down starches into smaller carbohydrate molecules (monosaccharides, disaccharides).

2. Pharynx: As food is swallowed, it is pushed by the tongue into the pharynx, which leads to the windpipe and esophagus.
      - The epiglottis covers the windpipe to prevent food from entering the respiratory system.

3. Esophagus: Food is passed to the stomach via muscular contractions known as peristalsis.

4. Stomach: The lining releases gastric juice (hydrochloric acid and proteases).
      - pH of the stomach is approximately 2, optimal for gastric enzyme activity.
      - Mucus secreted by stomach lining protects the wall from acidic gastric juice.
      - Smooth muscles mix the food, producing chyme, which is released into the small intestine through the pyloric sphincter.

5. Small Intestine: The primary site for digestion (up to 6 meters long) and absorption of nutrients.
      - Lined with villi to increase surface area for absorption.
      - Digestive enzymes are secreted by intestinal glands.
      - Liver produces bile stored in the gallbladder for fat breakdown.
      - Pancreas supplies various enzymes for digestion.

6. Large Intestine: Undigested food moves here, responsible for reabsorbing water.
      - Waste (feces) is stored in the rectum until defecation.
      - Diarrhea results from rapid peristalsis (inadequate water reabsorption).
      - Constipation results from slow peristalsis (excessive water reabsorption).

Circulatory and Lymphatic Systems

• Circulation: Internal transport of blood and lymph throughout the body, facilitating gas exchange, nutrient absorption, and waste disposal.

Cardiovascular System

1. Composed of the heart, blood vessels, and blood.

2. Heart Structure: Four chambers: two atria (receive blood) and two ventricles.
      - Blood enters right atrium from superior/inferior vena cavae.
      - Travels through tricuspid valve into right ventricle.
      - Pumps through semilunar valve into pulmonary arteries to lungs.
      - Newly oxygenated blood returns via pulmonary veins to left atrium.
      - Left ventricle pumps blood through the aorta to the body.

3. Blood Pressure: Generated by the heart; increases during contraction (systole) and decreases at relaxation (diastole).

Blood Composition

• Blood is a connective tissue: 45% cells (red blood cells, white blood cells, platelets), 55% plasma.

• Red Blood Cells (Erythrocytes): Transport oxygen.
    - Contain hemoglobin (iron-rich protein, approx 250 million molecules per cell).

• White Blood Cells (Leukocytes): Involved in immune defense; elevated levels indicate infection.

• Platelets: Key for blood clotting.

Blood Vessels

• Arteries: Carry blood away from the heart; muscular due to high pressure.

• Veins: Carry blood to the heart, with valves to prevent backflow.

• Capillaries: Connect arteries and veins; facilitate nutrient and waste exchange through thin walls.

Respiratory System

• Air enters through the nasal cavities to the pharynx, larynx, and trachea (windpipe) before branching into bronchi leading to the lungs.

• Alveoli: Functional units of the lung; gas exchange occurs here.

Gas Exchange

• Deoxygenated blood arrives via pulmonary arteries.

• Gas exchange occurs via diffusion across alveolar membrane: blood picks up oxygen and releases carbon dioxide.

Breathing Process

• Involves diaphragm and rib cage movements, changing chest cavity pressure to facilitate inhalation and exhalation.

• Exhaled air has higher CO2 concentration, can be demonstrated with lime water or bromothymol blue.

Cellular Respiration

• Formula: $C_6H_{12}O_6 + 6O_2 <br>ightarrow 6CO_2 + 6H_2O + ext{ATP}$ (aerobic respiration).

• Begins in cytoplasm, ends in mitochondria; aerobic respiration is efficient in energy production.

• Anaerobic Respiration: Occurs without oxygen; less efficient, produces lactic acid (sore muscles) or ethanol (in yeast fermentation).

Nervous System

• Regulates body functions and responds to stimuli.

• Neuron: Functional unit; generates impulses which travel from dendrites to axon terminals.
    - Types of Neurons:
      1. Sensory neurons: Transmit impulses from receptors.
      2. Motor neurons: Carry impulses to muscles and glands.

• Central Nervous System (CNS): Consists of the brain and spinal cord.

• Peripheral Nervous System (PNS): Transmits information to/from CNS; divided into somatic (external environment) and autonomic (internal environment like digestion).

• Reflex Arc: Simple, quick responses to stimuli, often bypassing the brain.

Brain Structure

1. Cerebrum: Largest part, responsible for high-level functions (thinking, speech, memory).

2. Cerebellum: Coordinates muscular activity and balance.

3. Brain Stem (Medulla): Controls homeostatic functions (temperature, blood pressure, breathing).

Endocrine System

• Maintains homeostasis through hormone secretions from ductless glands.
    - Hormones: Chemical messengers that influence growth, metabolism, and more.

Hormonal Mechanism

• Example: Insulin's release is triggered by increased glucose levels post-meal, facilitating glucose uptake by cells (negative-feedback mechanism).

Musculoskeletal System

• Comprises bones, connective tissue, and muscles; provides support, protection, and movement.

• Bone Structure: Made of osteocytes; more than 200 bones in the human skeleton.
    - Axial Skeleton: Skull, vertebrae, ribs, sternum.
    - Appendicular Skeleton: Bones of arms and legs.

Joints and Diseases

• Types of joints: Immovable (e.g., sutures in skull) and movable joints (e.g., ball-and-socket, hinge).

• Diseases:
    - Osteoarthritis (degenerative joint disease).
    - Rheumatoid arthritis (autoimmune condition).
    - Osteoporosis (calcium loss).

Muscles

• Types of muscle tissue:
    1. Cardiac Muscle: Involuntary, only in the heart.
    2. Smooth Muscle: Involuntary, in digestive tract and blood vessels.
    3. Skeletal Muscle: Voluntary, attached to bones; functions in movement.

• Muscles usually work in opposing pairs (flexor vs extensor).

Urinary System

• Kidneys: Principal excretory organs; consist of renal cortex (outer) and renal medulla (inner).

• Nephron: Functional unit; includes glomerulus, Bowman\'s capsule, tubules for filtration and reabsorption.

• Ureters transport urine to urinary bladder for storage; excreted through the urethra.

Reproductive System

• Involves the fusion of gametes (sperm and egg) to form a zygote; gametes are haploid, zygote is diploid.

Male Reproductive Organs

• External: Penis and scrotum.

• Internal: Testes (where sperm and testosterone are produced); sperm travels through the epididymis and vas deferens during ejaculation.

Female Reproductive Organs

• Ovaries produce eggs and hormones (progesterone, estrogen); egg maturation leads to ovulation.

• Following fertilization, the embryo implants into the uterine lining (endometrium) and develops.

Integumentary System

• Composed of skin, nails, hair, nerves, and glands; first line of defense against injury and infection.

• Skin structure: Three layers (epidermis, dermis, hypodermis).
    - The epidermis provides barriers; dermis contains connective tissue, blood vessels, and glands.
    - The hypodermis contains fat for temperature regulation and protection.

Senses

1. Sight: Involves cornea, iris, lens, and retina; rods (light sensitivity) and cones (color sensitivity).

2. Hearing: Ear anatomy consists of outer, middle (ossicles), and inner ear (cochlea); responsible for sound and balance.

3. Taste and Smell: Chemical receptors; taste buds detect basic tastes, olfaction (smell) is less developed in humans.

4. Touch: Detected through skin, varies in sensitivity and pressure detection.