What are the components of the urinary tract?
2 kidneys 2 ureters the bladder a urethra the urogenital system (penis/vulva)
What is a ureter?
Long tubes composed of 3 layers: the mucous lining, the muscular middle layer and the fibrous outer layer. They remove urine from kidneys down the the bladder.
What is the urinary bladder?
Predominately smooth muscle arranged in criss crossing bundles. Has a GAG lining that helps protect the epithelial cells from acidity. These cells allow contraction and extension. There is 1 exit and two entrances
What are the functions of the urinary bladder?
- acts as a reservoir for urine
- expels urine when it becomes full
What is the urethra?
A small tube that exits the bladder
What is the process of voiding urine?
Involves voluntary relaxation of the external sphincter, parasympathetic contractions of the muscular regions and the internal sphincter. Urine is then forced out through the urethra
Define the KIDNEY
The kidneys are each a pair of organs in the abdominal cavity that excrete urine
Define NEPHRON
A nephron is the functional unit in the kidney, consisting of the glomerulus and its associated tubule, through which the glomerular filtrate passes before emerging as urine. The loop of henle is in it.
Define the GLOMERULUS
The glomerulus is tufts of capillaries surrounded by Bowman’s capsules. It is a a major site for the filtration of blood. It filters 100 times as much liquid as urine is excrted.
What is the filtration rate?
The amount of filtrate that forms in all renal corpuscles every minute. For humans it is about 180l per day.
Define HOMESTASIS
Homeostasis is the process of maintaining a constant internal environment. Uses negative feedback:
- if pressure is too high, substances go through too fast and not enough is absorbed
- if pressure is too low, high levels of waste build up in the body
Define ANGIOTENSIN
Angiotensin is a protein whose presence in the blood tends to raise blood pressure. It constricts blood vessels and encourages the reabsorption of sodium and water, stimulating thirst.
Define the LOOP OF HENLE
The loop of henle is the part of the kidney tubule which forms a long loop in the medulla from which water and salt are reabsorbed into the blood.
Define OSMOSIS
Osmosis is the process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solutions to a more concentrated one
Define TUBULAR SECRETION
Tubular secretion is the process by which materials are removed from the blood such as excess potassium and hydrogen and foreign chemicals
Define VASOPRESSIN
Vasopressin is the hormone secreted from the posterior pituitary which controls permeability of the collecting duct. If it is absent, more dilute urine is formed as more water is secreted.
If it is present/increased, more concentrated urine is formed as more water is reabsorbed back into tissues.
What is a Bowman’s capsule?
A cup-like sack at the beginning of the tubular component of a nephron in the kidney that performs the first step in the filtration of blood to form urine.
Define the URINARY SYSTEM
The urinary system is a system whose main function is to remove waste products from the blood in the form of urine
