Comprehensive Human Anatomy and Physiology: Digestive, Respiratory, Circulatory, and Musculoskeletal Systems

What are the three main functions of the digestive system?

Ingestion and breakdown of food, absorption of nutrients, and elimination of waste.

What type of digestion occurs in the mouth?

Mechanical digestion (chewing) and chemical digestion (salivary amylase breaking down carbohydrates).

What is the primary function of the stomach?

Protein digestion using acid (HCl) and enzymes; mechanical churning.

What protects the stomach from its own acid?

A thick layer of mucus lining the stomach wall.

What is the major function of the small intestine?

Final digestion and most nutrient absorption.

Why are villi and microvilli important?

They increase surface area dramatically, improving nutrient absorption efficiency.

What does the liver contribute to digestion?

Produces bile, which emulsifies fats into smaller droplets for easier enzyme action.

What does the gallbladder do?

Stores and concentrates bile, releasing it into the small intestine.

What does the pancreas release into the small intestine?

Digestive enzymes (lipase, proteases, amylase) and bicarbonate to neutralize stomach acid.

What happens in the large intestine?

Water absorption, vitamin production by gut bacteria, and formation of feces.

What are essential nutrients?

Nutrients the body cannot synthesize and must obtain from food (essential amino acids, essential fatty acids, vitamins, minerals).

What is peristalsis?

Wave-like muscular contractions that move food through the digestive tract.

What is the main function of the respiratory system?

Gas exchange — bringing in oxygen and removing carbon dioxide.

What is the correct path of air into the lungs?

Nasal cavity → pharynx → larynx → trachea → bronchi → bronchioles → alveoli.

Why are alveoli essential for respiration?

They provide a large surface area and thin walls for efficient gas exchange with capillaries.

What is the role of hemoglobin?

A protein in red blood cells that binds and transports oxygen.

What does the right side of the heart do?

Pumps oxygen-poor blood to the lungs (pulmonary circulation).

What does the left side of the heart do?

Pumps oxygen-rich blood to the body (systemic circulation).

What are arteries, veins, and capillaries?

Arteries carry blood away from the heart; veins carry blood toward the heart; capillaries allow exchange of gases and nutrients.

Why is the circulatory system necessary?

It transports oxygen, nutrients, hormones, and removes waste products.

What is the purpose of the diaphragm?

A muscle that contracts to pull air into the lungs and relaxes to push air out.

What is the endocrine system's main function?

Regulating body processes using hormones released into the bloodstream.

What is a hormone?

A chemical messenger produced by endocrine glands that affects distant target cells.

What is a target cell?

A cell with specific receptors that bind a particular hormone.

What is negative feedback?

A regulatory mechanism where rising hormone levels signal the body to reduce production.

Give an example of negative feedback in the endocrine system.

Blood glucose regulation — one hormone lowers glucose, another raises it to maintain balance.

How do endocrine signals differ from nervous system signals?

Endocrine signals are slower but longer-lasting; nervous signals are fast and short-term.

What is the role of the pituitary gland?

Often called the 'master gland,' it releases hormones that control other endocrine glands.

What are the main functions of the skeletal system?

Support, protection of organs, movement, blood cell production, and mineral storage.

What is bone marrow?

Soft tissue inside bones that produces blood cells (red marrow) or stores fat (yellow marrow).

What connects muscle to bone?

Tendons.

What connects bone to bone?

Ligaments.

How do muscles create movement?

They contract, pulling on bones to produce motion.

What is the difference between smooth, cardiac, and skeletal muscle?

Smooth: involuntary, in organs; Cardiac: involuntary, in the heart; Skeletal: voluntary, attached to bones.

Why is calcium important for bones?

It provides structural strength and is stored/released to maintain blood calcium levels.

What is a joint?

A location where two bones meet, allowing movement.

What is osteoporosis?

A condition where bones lose density and become fragile.

What is chemical digestion?

The breakdown of food using enzymes and acids into molecules small enough to be absorbed.

What is mechanical digestion?

Physical breakdown of food into smaller pieces (chewing, stomach churning).

What is chyme?

The semi‑liquid mixture of partially digested food and stomach secretions.

What is the role of bicarbonate in digestion?

Neutralizes acidic chyme entering the small intestine from the stomach.

What is the function of the epiglottis?

Prevents food from entering the trachea during swallowing.

What is the function of the esophagus?

Moves food from the mouth to the stomach via peristalsis.

What is the function of the appendix?

A vestigial organ; may play a role in immune function and gut bacteria storage.

What is the role of gut bacteria in the large intestine?

Produce vitamins (like vitamin K), help break down undigested material.

What is emulsification?

The process of breaking fat into small droplets so enzymes can digest it more easily.

What is pulmonary circulation?

Blood flow from the heart to the lungs and back to the heart.

What is systemic circulation?

Blood flow from the heart to the rest of the body and back.

Why is the left ventricle thicker than the right?

It must pump blood to the entire body, requiring more force.

What is the function of platelets?

Help blood clot to prevent bleeding.

What is the function of white blood cells?

Fight infections and provide immune defense.

What is the purpose of the trachea's cartilage rings?

Keep the airway open and prevent collapse.

What is the role of the nasal cavity in respiration?

Warms, moistens, and filters incoming air.

What is tidal volume?

The amount of air inhaled or exhaled during normal breathing.

What is the role of carbon dioxide in breathing regulation?

Rising CO₂ levels trigger increased breathing rate.

How do hormones travel through the body?

Through the bloodstream to reach target cells.

What is the difference between endocrine and exocrine glands?

Endocrine glands release hormones into the bloodstream; exocrine glands release substances through ducts.

What is the role of the thyroid gland?

Regulates metabolism, growth, and energy use.

What is the role of the adrenal glands?

Produce stress hormones like adrenaline and cortisol.

What is the role of the pancreas in the endocrine system?

Regulates blood glucose by releasing hormones.

What is homeostasis?

The maintenance of stable internal conditions through feedback mechanisms.

Why do hormones only affect certain cells?

Only target cells have receptors that match the hormone.

What is positive feedback?

A process where a hormone increases its own production (rare; example: childbirth contractions).

What is the axial skeleton?

The bones of the skull, spine, and rib cage.

What is the appendicular skeleton?

The bones of the limbs, shoulders, and pelvis.

What is cartilage?

Flexible connective tissue that cushions joints and supports structures like the nose and ears.

What is a tendon?

A tough connective tissue that attaches muscle to bone.

What is a ligament?

A connective tissue that attaches bone to bone.

What is a sarcomere?

The basic contractile unit of muscle fibers.

What proteins are responsible for muscle contraction?

Actin and myosin.

What is the role of ATP in muscle contraction?

Provides energy for myosin to pull actin filaments.

What is the function of smooth muscle?

Controls involuntary movements in organs like the stomach and intestines.

What is the function of cardiac muscle?

Pumps blood through the heart; involuntary and highly resistant to fatigue.

What is the function of skeletal muscle?

Voluntary movement, posture, and heat production.