Glomerular Filtration

• The human body has two kidneys.
• Kidneys produce urine and regulate blood volume and composition.
• The human body has two ureters.
• Ureters drain urine from the kidneys.
• The urinary bladder collects and releases urine.
• The urethra drains the urinary bladder.
• Urine production involves glomerular filtration, tubular respiration, and tubular secretion.
• The glomerulus is a porous capillary bed acting as a strainer.
• Glomerulus filtration is the process of filtering blood at the glomerulus.
• Red blood cells (RBCs), white blood cells (WBCs), platelets, and proteins do not get filtered through the glomerulus because they are too large.

Glomerular Filtration

• Renal blood flow/perfusion drives the filtration process.
• Kidneys receive 1/4 of the heart's output.
• No blood flow to the kidneys results in no urine production.
• Blood volume influences blood flow.
• More blood flow leads to more filtration.
• Glomerular Filtration Rate (GFR) refers to the volume of filtrate produced by both kidneys per minute.
• Low blood volume (BV) or cardiac output (CO) decreases GFR.
• Low GFR decreases urine output (UO).
• High BV increases GFR, which in turn decreases BV.

Tubular Respiration

• Tubular respiration is the process where filtrate moves from the renal tube to the blood (peritubular capillaries), signifying substances to keep.
• The renal tube consists of Bowman's Capsule, proximal tubule, Loop of Henle, and distal tubule.
• The normal blood sodium (Na+) range is 135-145 mEq/L.
• A Na+ level of 140 results in normal filtration and reabsorption.
• A Na+ level of 150 results in filtration and less than normal reabsorption.
• A Na+ level of 120 results in filtration and more than normal reabsorption, along with aldosterone release.

Tubular Secretion

• Tubular secretion is the process where substances move from the blood (peritubular capillaries) to the filtrate (renal tube), signifying substances to lose.

Total Body Water

• Total Body Water (TBW) consists of 2/3 intracellular fluid (ICF) and 1/3 extracellular fluid (ECF).
• Extracellular fluid (ECF) consists of 80% interstitial fluid (between cells) and 20% plasma (bloodstream).
• Osmosis is the transfusion of water.
• The normal ECF & ICF concentration range is 280-300.
• Sodium (Na+) is the most abundant ECF solute.
• Water moving into a cell causes the cell to expand.
• Solvent is H2O.
• Solute is particles.
• High concentration occurs with normal solute and low solvent, or normal solvent and high solute.
• Low concentration occurs with normal solute and high solvent, or normal solvent and low solute.
• A concentration level of 300 is called hypertonic/hyperosmolar, indicating a concentrated state (low H20, high solute).
• Concentration levels refer to sodium (Na+) levels.
• Drinking lots of water dilutes the ECF, making it hypotonic.
• Eating salty food raises ECF concentration, making it hypertonic.
• In a traumatic brain injury (TBI), water moves out of the ECF and into brain cells (ICF) due to brain swelling, causing the ECF to become hypertonic/concentrated.
• Too much ADH release causes a hypotonic state, fluid shift from ECF to ICF, and cell expansion.
• Mild to moderate blood loss results in an isotonic state with no fluid shift, only a decrease in blood volume.

Digestive System

• The digestive system enables the body to take, breakdown, and absorb nutrients into the bloodstream.
• Mechanical digestion occurs in the mouth, where teeth cut, grind, and tear food.
• Chemical digestion occurs in the mouth, stomach, and small intestine.
• Food travels directly through the GI tract.
• The 5 main parts of the GI tract are the esophagus, stomach, small intestine, large intestine, and anus.
• The esophagus is a muscular tube that transfers food from the pharynx to the stomach; no digestion happens here.
• The stomach "liquifies" food into chyme for amino acid absorption, with chemical digestion occurring via secreted chemicals.
• Gastric refers to the stomach.
• The stomach secretes hydrochloric acid and mucus.
• Hydrochloric acid aids in chemical digestion to break down proteins, lipids, carbs, etc.
• Mucus coats the stomach lining to protect it from hydrochloric acid.
• Stomach ulcers result from insufficient mucus protection against hydrochloric acid.
• The small intestine is 18-20 feet long, where liquids travel through for amino acid absorption.
• The 3 parts of the small intestine are the duodenum, jejunum, and ileum.
• The duodenum is the first part of the small intestine where the stomach empties into; minimal chemical digestion happens here.
• The ileum is the last part of the small intestine that empties "formed" material into the large intestine.
• The large intestine absorbs water from waste as it travels through
• The large intestine consists of the cecum, ascending colon, right colic flexure/hepatic flexure, transverse colon, left colic flexure/splenic flexure, descending colon, sigmoid colon, and rectum.
• Accessory organs (liver, gallbladder, pancreas) contribute to digestion, but food does not pass through them directly.
• The liver produces bile, blood clotting factors, plasma proteins, and detoxifies NH3.
• Liver bile helps digest and absorb lipids; without bile, no lipids are absorbed.
• Hepatic refers to the liver.
• Albumin is the main plasma protein relevant to the digestive system, aiding in water retention.
• NH3 is ammonia.
• The gallbladder stores, collects, and releases bile into the duodenum.
• The pancreas has acinar cells that produce digestive enzymes for chemical digestion in the duodenum.