Respiratory / Excretory / Digestive — Key Terminology

1.Trachea is supported by C-shaped cartilage rings. Bronchus splits into left and right. Bronchioles have smooth muscle that can constrict — that is asthma. Alveolus is the gas exchange site, where surfactant reduces surface tension. Diaphragm contracts and descends during inhalation.

2.Oxyhemoglobin is oxygen bound to hemoglobin. Carbonic anhydrase catalyzes CO2 plus water to carbonic acid to bicarbonate plus proton — critical for CO2 transport.

3.Bohr effect: when pH drops, CO2 rises, or temperature rises, the oxygen dissociation curve shifts right — releasing more oxygen to active tissues like exercising muscle.

4.Nephron is the functional unit of the kidney. Glomerulus performs filtration — small molecules filtered from plasma. Bowmans capsule collects the filtrate.

5.Proximal convoluted tubule PCT: highest reabsorption — glucose, amino acids, sodium, bicarbonate, water. Loop of Henle establishes the medullary osmotic gradient via countercurrent multiplier.

6.Distal convoluted tubule DCT: regulated by aldosterone for sodium reabsorption and PTH for calcium reabsorption. Collecting duct: regulated by ADH for water reabsorption — concentrates urine.

7.Renin is secreted by the kidney and starts the RAAS system: Renin, Angiotensin, Aldosterone System.

8.Year one fourteen exam point: glomerular filtration only filters small molecules — water, electrolytes, glucose, amino acids, urea. Proteins and blood cells are NOT filtered. Protein in urine, called proteinuria, indicates glomerular damage.

9.Salivary amylase works at neutral pH and breaks down starch. Pepsin works at acidic pH around two and is activated from pepsinogen — digests protein in the stomach.

10.Pancreatic juice contains trypsin, lipase, amylase, and nuclease. Bile is produced by the liver, stored in the gallbladder, and emulsifies fat — note that bile contains NO enzymes.

11.Villi increase small-intestine absorption surface area. Microvilli, the brush border, further increase surface area. Lacteal is the lymphatic vessel that absorbs fat as chylomicrons.