Circulatory & Excretory Systems: Functions & Diseases
Circulatory System
Lymphatic System
The lymphatic system maintains body fluid balance and defends against infections.
- Lymph capillaries: Collect excess interstitial fluid.
- Lymphatic vessels: Return excess lymph to the circulatory system.
- Lymph nodes: Contain defense cells for fighting infection.
- Lymph: Acts as an intermediary in nutritional exchanges between blood and tissues.
Blood Circulatory System
The blood circulatory system defends against infections, facilitates gas exchange, and transports nutrients.
Blood Plasma
Blood plasma consists of water, nutrients, waste products, proteins, and hormones.
Blood Cells
- Red blood cells: Contain hemoglobin and transport oxygen.
- White blood cells: Help the body fight infections and diseases. Types include granulocytes (neutrophils, eosinophils, and basophils), monocytes, and lymphocytes (T cells and B cells).
- Platelets: Help blood coagulate.
Blood Circulation
- Arteries: Carry blood away from the heart to the organs.
- Veins: Carry blood back to the heart from the tissues.
- Capillaries: Connect veins and arteries.
Diseases of the Circulatory System
- Aneurysm: Dilation of a blood vessel, which can be fatal.
- Leukemia: Cancer that produces an excess of white blood cells.
- Anemia: Inability of the body to produce enough hemoglobin for red blood cells.
Excretory System
The excretory system facilitates the elimination of waste products generated by cell metabolism.
Excretion
Excretion is the process of eliminating waste products from cell metabolism from the blood.
- Kidneys: Produce urea and uric acid.
- Lungs: Produce carbon dioxide.
- Sweat glands: Produce sweat.
- Liver: Destroys toxins.
Urinary System
The urinary system eliminates waste products through urine. It consists of:
- Kidneys: Two bean-shaped organs located behind the abdomen, with a renal cortex, renal medulla, and renal pelvis.
- Urinary tract:
- Ureters: Two tubes connecting the kidneys to the bladder.
- Bladder: An elastic bag where urine accumulates.
- Urethra: Connects the bladder to the outside of the body.
Nephrons
Nephrons are the basic functional units of the kidneys, responsible for urine formation. Each kidney contains about one million nephrons.
- Glomerulus: A mass of tiny capillaries through which blood and waste products pass.
- Bowman’s capsule: A sac surrounding the glomerulus where water and salts are filtered.
- Proximal tubule: Reabsorbs glucose, amino acids, ions, vitamins, and filtered water.
- Loop of Henle: Reabsorbs ions and some water.
- Distal tubule: Reabsorbs ions.
- Collecting duct: Collects urine and transports it to the renal pelvis and then the ureter.
Urine Formation
Urine formation involves two main processes:
- Glomerular filtration: Water, glucose, vitamins, urea, and uric acid in blood plasma are filtered through Bowman’s capsule.
- Tubular reabsorption: The nephron removes water and solutes from the tubular fluid and returns them to the circulating blood.