Gastrointestinal, Endocrine, Renal, and Blood
Unit 1: Anatomy and Physiology. Lesson 5 of 60 in CBET Academy.
The remaining systems on the outline, each tied to devices you will maintain.
The gastrointestinal system
Food travels from the mouth down the esophagus to the stomach, then through the small intestine (duodenum, jejunum, ileum), where most absorption happens, and the large intestine, where water is absorbed, to the rectum. The liver processes nutrients and drugs and makes clotting factors; the pancreas supplies digestive enzymes and insulin; the gallbladder stores bile.
Devices: enteral feeding pumps deliver formula through nasogastric or gastrostomy tubes; suction clears the stomach or airway; endoscopes view the tract. Enteral connectors are deliberately incompatible with IV connectors so feeding formula cannot be injected into a vein.
The endocrine system
Glands release hormones into the blood. The pancreas releases insulin (lowers blood glucose) and glucagon (raises it); diabetes is too little insulin or resistance to it. The thyroid sets metabolic rate, the adrenals release epinephrine (adrenaline), and the pituitary directs the others. Devices: glucose meters and insulin pumps.
The renal system
The kidneys filter blood through millions of nephrons, removing waste and excess water as urine, which passes through the ureters to the bladder. They also balance electrolytes and blood pressure. When kidneys fail, dialysis takes over: blood passes through a semipermeable membrane against a fluid called dialysate, and waste diffuses out. The dialysis machine's job is to pump blood, mix and warm dialysate, and watch for leaks and air.
Blood
About five liters. Plasma is the liquid; red cells carry oxygen on hemoglobin; white cells fight infection; platelets clot. Laboratory analyzers count cells and measure chemistry; pulse oximetry works because oxygenated and deoxygenated hemoglobin absorb light differently. Blood must be stored at 2 to 8 C and warmed before rapid transfusion.
Immunity and infection
White cells and antibodies defend against pathogens. Hospital-acquired infections spread on hands and equipment, which is why infection control is a biomed's responsibility too.
When it goes wrong
Diabetes, renal failure, GI bleeding, liver failure, and anemia are the common conditions behind the equipment: feeding pumps, glucose meters, dialysis machines, blood warmers, and analyzers.
Gastrointestinal, Endocrine, Renal, and Blood, explained slowly
The systems behind the rest of the inventory
Feeding pumps, glucose meters, dialysis machines, blood warmers, and analyzers all serve the systems in this lesson. The outline wants normal function and the common abnormal function of each.
Gastrointestinal: a conveyor with chemical stations
mouth -> esophagus -> stomach (acid, churning) -> small intestine (duodenum, jejunum, ileum: ABSORPTION)
-> large intestine (water absorbed, stool formed) -> rectum
side stations: liver (processes nutrients and drugs, makes clotting factors, detoxifies)
pancreas (digestive enzymes into the gut; insulin into the blood)
gallbladder (stores bile for fat digestion)Device connections:
- Enteral feeding pumps push formula through a nasogastric tube (nose to stomach) or a gastrostomy tube (through the abdominal wall). They are lower-precision than IV pumps because the gut tolerates variation. Their connectors are deliberately shaped so an enteral syringe cannot connect to an IV line; formula in a vein is fatal.
- Suction clears stomach contents or the airway.
- Endoscopes view the tract; they are semi-critical devices requiring high-level disinfection and a leak test before reprocessing.
Abnormal: GI bleeding, obstruction, ulcers, liver failure (bleeding and confusion because clotting factors and detoxification fail).
Endocrine: chemical messengers
Glands release hormones into the blood, and the whole body listens.
pancreas insulin lowers blood glucose, glucagon raises it diabetes = not enough insulin or resistance to it thyroid sets metabolic rate too much: fast heart, heat; too little: slow, cold adrenals epinephrine (adrenaline), cortisol the fight-or-flight hormone; used in codes pituitary directs the other glands the "master gland"
Device connections: glucose meters (a drop of blood on a strip, an electrochemical reading, needs control solution checks and clean optics), insulin pumps (a small infusion pump with a reservoir and cannula). A normal fasting glucose is roughly 70 to 100 mg/dL; hypoglycemia is dangerous within minutes, hyperglycemia over days.
Renal: the filter
Each kidney contains about a million nephrons. Blood enters under pressure, water and small molecules are filtered out, the useful ones are reabsorbed, and the waste leaves as urine through the ureters to the bladder. The kidneys also balance sodium and potassium, control blood volume and pressure, and stimulate red cell production.
When they fail, waste and fluid build up. Hemodialysis does the filtering outside the body:
patient blood --> blood pump --> [DIALYZER: thousands of hollow fibers, a semipermeable membrane]
blood inside the fibers | dialysate flowing outside, opposite direction
waste and excess water cross the membrane by diffusion and pressure
<-- air detector and venous clamp <-- warmed, clean blood returns
dialysate: treated water (reverse osmosis) mixed with concentrate; conductivity about 13 to 14 mS/cm;
temperature about 35 to 38 C; a blood leak detector watches for a ruptured fiberThe machine's alarms exist because each failure is lethal: air in the return line, wrong conductivity (electrolyte disaster), wrong temperature, a membrane leak.
Blood: the transport system
About 5 liters. Plasma is the liquid carrying proteins and clotting factors. Red cells carry oxygen on hemoglobin; their count and hemoglobin level define anemia. White cells fight infection; their count rises with infection. Platelets start clots. Laboratory analyzers count and size these cells and measure plasma chemistry. Blood for transfusion is stored at 2 to 8 C and must never be warmed above about 42 C; blood warmers have an over-temperature cutoff for that reason. Pulse oximetry works because oxygen-carrying hemoglobin is a different color from hemoglobin without it.
Immunity and infection
White cells and antibodies recognize and destroy invaders. Patients in hospitals are often immunocompromised, which is why a contaminated blood pressure cuff or ventilator circuit can cause a serious infection, and why the biomed's cleaning habits are patient safety.
How the exam asks it
- "Which organ produces insulin?" The pancreas.
- "By what process does waste cross the dialyzer membrane?" Diffusion.
- "Why are enteral connectors different from IV connectors?" To prevent feeding formula from being given intravenously.
- "Storage temperature for blood products?" 2 to 8 C.
What to memorize
- Absorption in the small intestine; liver processes and makes clotting factors; pancreas makes insulin.
- Kidneys filter through nephrons; dialysis diffuses waste across a membrane; conductivity, temperature, air, and blood leak alarms.
- Blood: plasma, red (hemoglobin), white, platelets; store at 2 to 8 C.