BIO 105: General Biology - Digestive, Urinary, Cardiovascular, and Respiratory Systems

Digestive System

Functions

• Digestion: Breaks down food into usable forms.
• Absorption: Transfers nutrients to blood circulation.
• Excretion: Eliminates waste.
• Ingestion: Allows food consumption.

Organs and Structures

• Digestive Tract: Muscular tube from mouth to anus.

• Accessory Organs: Support the digestive tract; include salivary glands, gallbladder, liver, pancreas.

• Mouth (Oral Cavity):

  • Teeth reduce food size, increasing surface area.
  • Saliva enzymes break down carbohydrates.

• Pharynx: Connects oral cavity to esophagus; the epiglottis blocks the windpipe.

• Esophagus: Transports food to the stomach via peristalsis.

• Stomach:

  • Acidic gastric juices break down food.
  • Pepsin breaks down proteins.
  • Mucus protects stomach lining.
  • The pyloric sphincter regulates food movement to the small intestine.

• Small Intestine:

  • Most digestion of carbohydrates, proteins, and fats occurs here.
  • Nutrients are absorbed into the bloodstream.
  • Regions: Duodenum, Jejunum, Ileum.
    • Duodenum: Receives chyme and secretions from the pancreas and liver.
    • Jejunum: Primary region for digestion and nutrient absorption.
    • Ileum: Absorption continues.

• Large Intestine:

  • Water is reabsorbed.
  • Compacts undigested material into feces.
  • Absorbs vitamins produced by resident bacteria (gut microbiome).

• Rectum: Waste storage.

• Anus: Waste excretion.

Accessory Digestive Organs

• Liver:
  • Produces bile, which aids in fat absorption.
  • Helps metabolize toxins.
  • Controls nutrient storage and circulation.
• Gallbladder: Stores and concentrates bile which then empties into the small intestine.
• Pancreas:
  • Produces digestive enzymes to break down fats, proteins, and carbohydrates.
  • Secretes buffers to neutralize acidic chyme.

Processes

• Peristalsis: Rhythmic contractions of smooth muscles that push food along.
• Sphincters: Valves that regulate movement between compartments.
• Chyme: Mixture of food and digestive juices leaving the stomach.

Absorption

• Small Intestine: Primary site of nutrient absorption (90%).
• Intestinal Folds, Villi, and Microvilli: Increase absorption surface area.
• Capillaries: Absorb carbohydrates and proteins.
• Lymphatic Vessels: Absorb fats.

Transit Times (Vary Widely)

• Mouth: Less than a minute.
• Stomach: Approximately 1-2 hours.
• Small Intestine: Approximately 7-8 hours.
• Large Intestine: Approximately 12-14 hours.

Urinary System

Functions

• Filters bodily fluids.
• Removes waste.
• Conserves water and materials.
• Regulates blood volume

Major Organs

• Kidneys: Produce urine; contain approximately 1 million nephrons each.
• Ureters: Transport urine to the urinary bladder.
• Urinary Bladder: Temporarily stores urine.
• Urethra: Transports urine out of the body.

The Nephron

• Functional unit of the kidney.

Processes

• Filters waste materials from the blood.
• Conserves useful materials, such as water, nutrients, and ions.

Cardiovascular System

Components

• Heart
• Blood vessels (arteries, veins, capillaries)
• Blood
• Bone marrow (where blood cells are formed)

Functions

• Transports substances (oxygen, carbon dioxide, nutrients, hormones, waste products, immune system cells) to and from body cells.

Blood Composition

• Formed Elements (45%):
  • Red blood cells (99.9%): Carry oxygen and carbon dioxide.
  • White blood cells (0.1%): Central to the immune system.
  • Platelets: Important in blood-clotting.
• Blood Plasma (55%):
  • Water (92%)
  • Plasma proteins (7%): Albumins, Fibrinogen, Globulins
  • Other solutes (1%)

Plasma Proteins

• Albumins: Transport hormones and fatty acids, maintain osmotic pressure.
• Fibrinogen: Aids in blood clotting.
• Globulins: Aid the immune system, serve as transport proteins.

Blood Vessels

• Arteries: Carry blood away from the heart.
• Veins: Return blood to the heart; contain valves to prevent backflow.
• Capillaries: Connect arteries with veins; composed of a single layer of cells for material exchange.

Circulation Loops

• Pulmonary Circulation: Blood circulates between the heart and lungs (oxygenation).
• Systemic Circulation: Blood circulates between the heart and the rest of the body (transport of materials).

Heart Chambers

• Right Atrium and Right Ventricle: Pulmonary circulation.
• Left Atrium and Left Ventricle: Systemic circulation.
• Valves ensure one-way blood flow.

Heart Rate Control

• Sinoatrial node generates electrical signals to prompt muscle contraction.

Heart Attacks

• Caused by blockage of coronary arteries due to plaque buildup and blood clot formation.

Respiratory System

Functions

• Captures oxygen and disposes of carbon dioxide.
• Aids in controlling pH balance in the bloodstream.
• Produces sounds for speaking.

Components

• Nose, nasal cavity, and sinuses
• Pharynx (upper throat)
• Larynx (voice box)
• Trachea (windpipe)
• Conducting passageways (bronchi and bronchioles)
• Lungs (composed of alveoli)

Processes

• Ventilation (Breathing): Physical movement of air into and out of the lungs.
• Gas Exchange: Exchange of oxygen and carbon dioxide.

Gas Exchange Details

• Oxygen diffuses from alveoli to capillaries and binds with hemoglobin in red blood cells.
• Carbon dioxide moves from body cells into capillaries to be carried to the lungs.

Organ System Interconnections

• Respiratory System: Moves O2 into, and CO2 out of, the body.
• Cardiovascular System: Transports materials to and from all other systems.
• Digestive System: Transforms food into a transportable form.
• Urinary System: Filters fluids and removes waste.