Human Physiology: Blood, Heart, and Excretory Systems
Topic 4: The Internal Environment
Interstitial Plasma: A liquid that originates from blood that has been filtered through the capillaries.
Blood: The medium for the transport of substances that runs inside blood vessels.
Lymph: A liquid that is formed from interstitial liquid and circulates through the vessels and nodes.
Blood Vessels
- Arteries: Carry blood from the heart to the organs.
- Veins: Carry blood from the organs to the heart.
- Capillaries: The union between veins and arteries.
Blood Functions and Composition
Primary Functions
- Nutrition: Carries nutrients.
- Breathing: Participates in the exchange of gases.
- Excretion: Drives the excretory system regulation.
- Defense: Protects the body.
- Thermal: Plays a role in stabilizing the body temperature.
Blood Composition
Blood is composed of Plasma and Blood Cells:
- Erythrocytes: Contain hemoglobin. They transport oxygen from the lungs to the cells.
- Leukocytes: Defensive functions.
- Thrombocytes: Involved in the processes of blood coagulation.
The Cardiac Cycle and Heart Operation
- Diastole: Blood enters the right atrium through the vena cava and the left atrium through the pulmonary veins.
- Atrial Systole: The atria contract and the valves open; blood passes into the ventricles.
- Ventricular Diastole: The ventricles swell to receive blood from the atria.
- Ventricular Systole: The ventricles contract and the semilunar valves open. Blood is propelled from the left ventricle into the aorta and from the right ventricle to the pulmonary artery.
The Lymphatic System Structure
- Lymphatic Capillaries: These are small, thin, blind-ended vessels found in all tissues.
- Lymphatic Vessels: Vessels similar to veins that flow into the circulatory apparatus.
- Lymph Nodes: Small swellings of the lymph vessels.
The Urinary and Excretory Systems
The Urinary System
- Kidneys: Two organs located in the posterior abdominal region. They filter the blood to remove waste substances, producing urine.
- Urinary Tract: Conduits that carry urine from the kidneys to the exterior, including the ureters, bladder, and urethra.
Other Excretory Organs
- Lungs: Remove CO2.
- Liver: Expels waste from digestion.
- Sweat Glands: Exocrine glands located in the skin.
Nephron Function and Urine Formation
The Nephron:
- Glomerulus: A crowding of capillaries.
- Bowman's Capsule: A bag surrounding the glomerulus.
- Renal Tubule: A hairpin-shaped tube that reabsorbs water.
- Collecting Duct: A tube common to several nephrons.
Urine Formation:
- Filtration: The passage of substances from blood plasma through the capillaries of the glomerulus.
- Reabsorption: The passage of filtered substances back into the blood.
Unit 1: Levels of Biological Organization
The levels of organization are: subatomic, atomic, molecular, cell, tissue, organ, system, apparatus (machine), and body.