Urinary System Flashcards
What are the three basic functions of the kidney and urinary tract?
1) Maintain water and electrolyte homeostasis, body fluid osmolarity and acid-base balance
2) Excrete toxic metabolic waste products (mainly urea and creatinine) 1 and 2 achieved by production, storage and voiding of urine
3) Act as an endocrine gland, producing renin and erythropoietin
Basic Kidney Structure
- Capsule
- Thin but strong. Dense collagen fibres.
Calyces
- Pelvis
- Pelvis expands from ureter to form calyces
What is this?
Nephron
Renal Papilla
Nephron
What is it?
What is it composed of?
The basic functional unit of the kidney.
Composed of the renal corpuscle and renal tubes
Renal Corpuscle
Formed from
A tuft of capillaries (glomerulus) and the cup of simple squamous epithelium at the blind end of the nephron, which the capillaries invaginate into (bowmans capsule)
Renal Corpuscle
Vascular supply
Supplied by an afferent arteriole and drained by an efferent arteriole
Renal Corpuscle
Podocytes
Specialised epithelium lying on top of glomelular capillaries. Have interdigitating cell processes which form filtration slits, and form one of the two cell layers separating the blood from the glomelular filtrate. The other layer is capillary endothelium
Renal Corpuscle
Basal lamina
Between the two layers separating glomelular filtrate and blood. Thicker than usual and made up of a feltwork of GAG’s
Renal Corpuscle
Mesangial cells
Sit within space between endothelial cells and the basal lamina which surrounds the entire complex, and eats the stuff which gets stuck in the pores. Also control filatration rate.
Proximal Convoluted Tubule (PCT)
Role
Microvili
Reabsorbtion of water, proteins, amino acids, carbohydrates and glucose. Most stuff is put out of the body but the good stuff brought back in from glomelular filtrate.
Are the hallmark of proximal convoluted tubules
Loop of Henle
Function
Creates a hypertonic environment in the medulla by changing the extratubular environment
Loop of Henle - Vasa Recta
- Why have it?
Blood vessels moving normally to the medulla would flush away all the salts, destroying the osmotic gradient. This has been solved by loops of blood vessels (vasa recta) dipping into the medulla and returning to the cortex.
This means that the salt will go back into the area around the loop of henle on the way back up
What happens in the medulla?
Permeabilities change in the loop of henle as it dives down and comes back up.Thin limb goes down and thick goes up. Thick is not permeable to water but thin is permeable to almost everything.This means there is a very high osmotic pressure created in the medulla.
Structures in the medulla
Thick limb has lots of mitochondria
Distal Convoluted Tubule
Function
Acid-base and water balance (absorption of water, Na, and bicarbonate, excretion of K and H ions. Fine tunes the acid-base and water balance in the system.
Collecting duct
Urine dripped off from the end of it and into the calyx. Controlled reabsorption of water under the control of ADH.ADH can cause the duct to vary the permeability to water, meaning that you can regulate the amount of water being put out.
Juxtaglomerular Apparatus
Macula densa
On the side of the DCT nearest the afferent arteriole, the cells of the DCT are taller. Function believed to be in sensing sodium content in the DCT.
Juxtaglomerular Apparatus
Juxtaglomerular cells
Modified smooth mucscle cells in wall of the afferent arteriole. These cells contain/excrete renin, initiating the renin-angiotensis system
Juxtaglomerular Apparatus
Extraglomerular mesangial cells/lacis cells
Modified mesangial cells which extend outside the renal corpuscle. They contact the macula densa and are continuous with the mesangial cells inside the renal corpuscle. They are thought to function in signalling that alters glomerular filtration, but the exact function is unknown.
Urothelium (transitional epithelium)
Lining of the conducting parts of the urinary tract. Stratified and found in 3-6 cell layers. Umbrella domed cells at the surface. This gives a very highly impermeable and inflexible membrane. Layers of smooth muscle below the epithelium.
What is this?
Urinary bladder
What is this?
Renal papilla
