Kidneys, Blood, Skin, Digestion, and Hormones
Unit 2: Anatomy, Physiology, and Medical Terminology. Lesson 8 of 53 in BMET Academy.
Four more systems, each with equipment attached. None of them need depth; they need the one idea per system that explains the devices.
Kidneys and the urinary system
Two kidneys filter the entire blood supply over and over, pulling out urea and the rest of the body's waste along with extra water and sending it on as urine through the ureters to the bladder. Each kidney does that with about a million microscopic filters called nephrons, which is why kidney disease usually shows up as a gradual loss of filtering rather than an on-or-off failure. They also hold the body's water, salt, and acid balance steady. When kidneys fail, a dialysis machine does the filtering instead: blood out of the patient, through a filter, and back. That machine is a water treatment plant, a pump, a heater, and a set of alarms, and it is one of the most heavily maintained devices in a hospital. A bladder scanner uses ultrasound to measure how much urine is left behind without a catheter.
Blood
An adult carries roughly five liters of blood. Lose enough of it and pressure falls no matter how well the heart works. Blood comes in types, A, B, AB, and O, each either positive or negative, and the type must match before a transfusion. Type O negative is the one most often given when there is no time to check. For you, blood matters two ways: the devices that warm it, pump it, and spin it in the laboratory, and the fact that every patient's blood is treated as infectious.
Skin
Three layers: the epidermis on the outside, the dermis underneath with the blood vessels and nerves, and the subcutaneous fat below that. Skin is a barrier against infection, a thermostat whose sweat glands and flushing shed heat as part of the body's thermoregulation, a sense organ, and the place the body makes vitamin D in sunlight.
Skin is also an electrical component. Dry, intact skin is a good insulator, roughly 100,000 ohm between two points on the body. Wet it with sweat, water, or electrode gel and that can fall toward 1,000 ohm. The same 120 V is a hundred times more dangerous against wet skin, which is the single most useful safety fact in this course. It also explains your devices: an electrode deliberately lowers skin resistance with gel so a tiny signal can get out, an electrosurgical return pad or a warming blanket can burn skin if the heat or current concentrates, and a cuff, a probe, or a mattress left in one place too long causes a pressure injury.
Digestion
A long tube: mouth, esophagus, stomach, small intestine, large intestine, with the liver adding bile to break up fat and the pancreas adding digestive enzymes. Food is broken down and absorbed, and what is left is waste. The devices are feeding pumps that deliver formula into the stomach or intestine, suction to remove fluid, and endoscopes, flexible cameras that let a clinician look inside the tube and work through it.
Hormones
The endocrine system is a set of glands (pancreas, thyroid, adrenals, pituitary) that release hormones into the blood as chemical messages. Slower than nerves, but they reach everywhere. The one you will meet constantly is insulin from the pancreas, which lets cells take up glucose from the blood. Too little insulin and blood sugar climbs. Hence glucometers, the handheld meters that read a drop of blood, and insulin pumps, which deliver tiny continuous doses.
The thyroid sets the body's metabolic speed, which includes body temperature. Normal core temperature is 37 C, which is 98.6 F.
Kidneys, Blood, Skin, Digestion, and Hormones, explained slowly
Kidneys: the filter
Blood enters each kidney, passes through about a million microscopic filters, and leaves cleaner. What is pulled out, waste and surplus water, becomes urine and drains to the bladder. Beyond cleaning, the kidneys hold the body's water, salt, and acid balance steady and help regulate blood pressure, which is why kidney failure affects the heart almost immediately.
Dialysis replaces that filtering mechanically: blood is pumped out of the patient, across a membrane with cleaning fluid on the other side, and returned. For a technician a dialysis machine is a pump, a heater, a water treatment system, a set of pressure and conductivity sensors, and a long list of alarms, each of which protects the patient from a specific failure. A bladder scanner is the opposite end of the complexity scale: a handheld ultrasound that measures retained urine volume so a nurse can avoid an unnecessary catheter.
Blood
About five liters in an adult. Enough loss and pressure falls no matter how strong the heart is, which is what the fluid warmers, rapid infusers, and transfusion devices in a trauma bay exist to address.
Blood type Notes A, B, AB, O each is positive or negative for the Rh factor O negative given when there is no time to type and cross-match AB can receive the most types Volume about 5 liters in an adult
Skin, the component
Three layers: epidermis outside, dermis with vessels and nerves beneath it, subcutaneous fat below. Skin is a barrier against infection, a temperature control system that sweats and flushes, and a sense organ.
For your purposes, it is also a resistor whose value changes with the weather.
Condition Approximate resistance Current from 120 V dry, intact skin about 100,000 ohm about 1 mA, a tingle wet, sweaty, or broken about 1,000 ohm about 120 mA, likely fatal
Three device families follow from that. Electrodes deliberately lower skin resistance with gel and abrasion so microvolt signals can escape. Electrosurgery units pass current through tissue on purpose and return it through a large pad, so a pad partly lifted concentrates the current in a small area and burns; warming devices burn the same way when heat concentrates. And any cuff, probe, or mattress left pressing one spot too long causes a pressure injury, which is why bed and mattress maintenance is patient safety work and not janitorial work.
Digestion
A tube from mouth to the far end, with the liver and pancreas adding chemicals along the way. Food is broken down, absorbed through the intestinal wall, and the remainder leaves. The devices are feeding pumps, whose connectors are deliberately incompatible with intravenous sets so formula can never be sent into a vein, suction for removing fluid, and endoscopes, flexible cameras threaded into the tube for both looking and working. Endoscopes are also the single most demanding item in the hospital for cleaning and disinfection, with their own documented reprocessing cycle.
Hormones
The endocrine glands (pancreas, thyroid, adrenals, pituitary) release hormones into the blood as slow chemical messages that reach the whole body. Insulin from the pancreas lets cells take up glucose; without enough of it, blood sugar climbs. That gives you glucometers, handheld meters read from a drop of blood and subject to quality-control checks like any laboratory instrument, and insulin pumps, which deliver microliter doses continuously and therefore demand the same flow accuracy discipline as any other pump. The thyroid sets metabolic rate, which includes heat production, and normal core temperature is 37 C, or 98.6 F.