Histology Flashcards
What are the functions of the kidneys and urinary tract
Maintain water and electrolyte homeostasis, body fluid osmolarity and acid-base balance
Excrete toxic metabolic waste products - urea, creatinine etc
Act as an endocrine gland - renin and erythropoietin
What hormones does the kidney release
Renin - enzyme involved in BP control
Erythropoietin - related to maintenance and production of RBC
What covers the kidney
Strong capsule of dense collagen fibres
How is the medulla divided
Into 8-18 medullary pyramids
Apices point toward the hilum - end in papillae which drain into the minor calyx
What is a nephron
Basic functional unit of the kidney
Composed of renal corpuscle and the tubules
What is the function of the renal corpuscle
Production and collection of the glomerular filtrate
What forms the renal corpuscle
Collection of capillaries called the glomerulus
Part of the nephron lined by squamous epithelium - forms a cup called Bowman’s capsule
The capillaries invaginate into the capsule
What are podocytes
Specialised epithelial cells that lie on top of the glomerular capillaries
They have interdigitating, ‘feet-like’ processes that form slits for the filtrate to get through
Describe the endothelium of the glomerular capillaries
It is fenestrated (has pores) to allow for easy fluid movement
List the layers that filtrate from the glomerular capillaries must pass through to reach the nephron
Endothelium of the capillary
Thicker basal lamina
Podocyte processes
What is the mesangium
Connective tissue core to the corpuscle formed by scattered mesangial cells
Involved in support and the removal of debris
Glomerular filtrate is similar in volume to the amount of urine left at the end of the process
FALSE
Much greater as lots is reabsorbed in the rest of the system
What is the function of the proximal convoluted tubule
Reabsorption of water, proteins, amino acids, carbohydrates and glucose.
The proximal convoluted tubule has lots of microvilli - true or false
True
They increase the surface area for reabsorption
How doe a proximal convoluted tubule appear on histology
Cross section has a fizzy inner border due to all the microvilli
What type of cell lines the proximal convoluted tubule
Cuboidal epithelial cells
Describe the structure and lining of the loop of Henle
Starts off wide and lined by cuboidal but becomes a very thin tube lined by squamous – becomes thick again when you reach the top of ascending limb
It starts in the cortex, dives down into the medulla and then up again
What is the function of the loop of Henle
Creation of hyperosmotic environment in medulla
Very salty
What are the vasa recta
Specialised blood vessels that follow the same path as the loop of Henle - dive down into medulla they head back up
They are designed not to disrupt the osmotic gradient in the loop
What is the function of the distal convoluted tubule
acid-base and water balance (absorption of water, Na and bicarbonate, excretion of K and H ions).
What controls reabsorption in the distal convoluted tubule
Aldosterone which is released by the adrenal cortex
Where is the collecting duct found
It connects to the distal tubule of the nephron and then dives back down to through the medulla to the tip of the pyramid
Here, urine drips off into the minor calyx
What hormone acts in the collecting ducts
ADH
It increases permeability of the duct to cause more reabsorption of water
What type of epithelium lines the urinary tract
Transitional epithelium
AKA urothelium
highly specialised to form an impenetrable barrier – stops any components of urine getting back into the body
Have the capacity to move over each other and thicken the lining
Who has the longer urethra - men or women
Men
Male urethrea is 20cm
Female is 3-5cm
What lines the female urethra
Transitional epithelium that becomes stratified squamous near the termination
What lines the male urethra
In prostatic it is transitional
In membranous it changes to stratified columnar
In penile it is stratified columnar and becomes stratified squamous near the tip
