Histology and embryology Flashcards
What are the functions of the kidney and the urinary tract?
- maintain water and electrolyte homeostasis, body fluid osmolarity and acid base balance
- excrete toxic metabolic waste products (mainly urea and creatinine)
- act as an endocrine gland, producing renin and erythropoietin
What is the hilum of the kidney?
- site of entry of renal artery
- exit of renal vein and ureter
What is considered a lobe of the kidney?
Each medullary pyramid and its associated cortical tissue
Name the two layers of the capsule
- outer fibrous layer
- inner cellular layer
The glomeruli is only present within what?
The cortex
What is the basic functional unit of the kidney?
The nephron
The nephron is composed of what?
The renal corpuscle and renal tubules
What is the principle role of the renal corpuscle?
The production and collection of glomerular filtrate
What is the principle role of the proximal convulated tubule?
Reabsorption of water, proteins, amino acids, carbohydrates and glucose
What is the principle role of the loop of henle?
The creation of hyperosmotic environment in medulla
What is the principle role of the distal convulated tubule?
Acid-base and water balance (absorption of water, Na and bicarbonate, excretion of K and H ions)
The renal corpuscle is formed from what?
Formed from a tuft of capillaries called the glomerulus and the cup of simple squamous epithelium at the blind end of the nephron which the capillaries invaginate into (called the bowmans capsule)
Describe the two cell layers which separate the blood from the glomerular filtrate
- the capillary endothelium and a specialised epithelium which lies on top of the glomerular capillaries
- these epithelial cells are called podocytes
- the endothelium is fenestrated with pores 70-90nm in diameter, and the podocytes have interdigitating cell processes forming filtration slits about 25nm wide
- between these two layers is a thicker than usual (0.3 micrometres rather than 0.05) basal lamina
Scattered mesangial cells produce what?
- produce a connective tissue core called the mesangium
- these cells have several functions, including support and removal of debris
Name the three components of the glomerular filter
- the fenestrated endothelium of the capillary wall
- the thick basement membrane (shared by endothelium and podocyte)
- the filtration slits between pedicles
Describe the histology of a proximal convulated tubule cell
- simple cuboidal cells
- very florid apical brush border which increases surface area
- interdigitations of basal membranes which increases surface area
The medulla is made up of what?
- parallel tubules
- the loops of henle
- the collecting ducts
- as well as a looping vascular network
Describe the portions of the loop of henle
- initial portion is a thick descending limb
- thin descending limb (hair pin turn)
- thin ascending limb
- then ascending limb (straight portion of the distal tubule which then becomes the distal convulated tubule)
The thick limbs are lined by what?
Simple cuboidal epithelium
The thin limbs are lined by what?
Simple squamous epithelium
Reabsorption of Na+ in the distal convulated tubule is controlled by what?
Aldosterone
What is the role of the collecting tubules and collecting ducts?
Reabsorption of water under the control of ADH
What increases the permeability of the collecting duct to water?
ADH (vasopressin)
Describe the flow of urine
- the urine produced at the renal papilla is collected into the minor calyx
- flows into major calyx
- then ureter
- and then into the bladder - during voiding it flows into the urethra and exits the body
