Renal Histology Flashcards
What are the functions of the kidney and renal tract?
Maintain water and electrolyte homeostasis, body fluid osmolarity and acid-base balance
Excrete toxic metabolic waste products
Act as an endocrine gland to produce renin and erythropoietin
What covers the kidney?
Fibrous capsule which is continuous with the connective tissue that lines the renal sinus
What is the nephron made up of?
Renal corpuscle (glomerulus and bowman’s capsule) and renal tubules (proximal convoluted tubule, loop of henle and distal convoluted tubule)
What is the function of the renal corpuscle?
Production and collection of glomerular filtrate
What type of epithelium is bowman’s capsule?
Simple squamous epithelium
What cell layers separate the blood from the glomerular filtrate?
Capillary endothelium and a specialised epithelium which lies on top of the glomerular capillaries - podocytes
What type of capillary is present at the glomerulus?
Fenestrated endothelium
What do mesangial cells produce?
Connective tissue core called the mesangium
What is at the apical and basal poles of a renal corpuscle?
Vascular pole
Urinary pole - into the proximal convoluted tubule
What must filtrate from the blood pass through to reach the medullary apex?
Endothelium fenestration Basal lamina (made up of GAGs) Filtration slits of podocytes
What is the function of the proximal convoluted tubule?
Reabsorption of water (70% of sodium and water reabsorbed) proteins, amino acids, carbohydrates and glucose
What is special about the apical and basal membrane of the cells in the proximal convoluted tubule?
Cuboidal cells with a brush border to allow for a large SA - maximal amount of absorption
What is the function of the loop of henle?
Creation of hyperosmotic environment in medulla
What makes up the loop of henle?
Thick descending limb (simple cuboidal epithelium)
Thin descending limb (simple squamous epithelium)
Thin ascending limb
Thick ascending limb
How is the medulla supplied with blood?
Thin walled blood vessels that dip down into the medulla from above and then climb back up to the cortex
Loops of blood vessels are called the vasa recta
What is the function of the distal convoluted tubule?
Acid-base and water balance (absorption of water, sodium and bicarb, excretion of potassium and hydrogein ions)
Describe the cells in the distal convoluted tubule?
Small villi at the apical membrane
Large villi at the basal membrane
What controls the reabsorption of sodium in the distal convoluted tubule?
Aldosterone, secreted by the adrenal cortex and results in greater sodium and water retention and therefore it increased BP
What is the function of the collecting ducts?
Reabsorption of water under the control of ADH
Where does the collecting duct end?
Medullary papilla at the apex of the medullary pyramid - duct of bellini
How does ADH control the collecting ducts?
ADH increases the permeability of the collecting duct to water
In the presence of high ADH (hot day with low water intake), permeability of the duct is high during passage through the medulla and because of the high salt content in the surrounding tissue, water passes out of the lumen and a concentrated urine results
How does the urine go from the renal pyramids to exiting the body?
Renal papilla Minor calyx Major calyx Bladder via ureteric orifices Urethra via internal urethral orifice
What type of epithelium lines the conducting areas of the urinary tract?
Transitional epithelium - stratified made up of 3-6 layers
What are the cells at the luminal surface of the urinary tract called?
Umbrella cells because they are domed
What smooth muscle lines the bladder?
Detrusor muscle which is responsible for micturition, and the internal urethral sphincter
What nerves control the micturition reflex?
Parasympathetic ganglia by neurones in the sacral spinal cord in the muscle and adventitia
What lines the urethra in females?
Initially transitional then stratified squamous near its termination
What lines the urethra in males?
Prostatic: transitional
Membranous: stratified columnar
Penile: stratified columnar becomes stratified squamous
