Histology Of Urinary System 2 Flashcards
How do renal tubules modify Glomerular ultrafiltrate ?
- Reabsorption
- Secretion
- Reduces urine volume
- Creates a hyperosmotic fluid
Describe the structure of proximal straight henle
Also called thick descending portion of loop of Henle
- Found in the medullary ray of the cortex. Also found in outer medulla
- Shorter cells with poorly developed brush border and less complex basolateral and lateral interdigitations than the PCT’s
- Fewer and smaller mitochondria scattered throughout the cytoplasm
Where are thin segment of loop of henle located?
Longer in juxtamedullary nephrons and are found in the medulla
Describe the structure of thin segment of loop of henle
-Four distinct segment based on shape of cells, their contents of organelles, the depth of their tight junctions, and their water permeability
Epithelium varies from:
-thin simple squamous in both ascending and descending limbs in short nephrons
Squamous cells are modified in…
Certain parts of the loop of henle
Describe the vasa rectus and countercurrent exchange system of the nephron
Arteriole and venule rectae form loops parallel to the loop of Henlé (fenestrated capillaries)
Help maintain osmotic gradient in the interstitium
Hypertonic interstitium
- causes loss of water from the arterioles as they descend into medulla
- Movement of water into the venules as they ascend
Where is the distal straight tubule found?
Found in the medullary ray of the cortex. Also found in outer medulla
Describe distal straight tubule
Shorter cells with blunted brush border and less complex basolateral and lateral interdigitations
Smaller cells with less mitochondria scattered throughout the cytoplasm
What are the distal straight tubule of loop of henlé?
Also called thick ascending limb
- Cortical part found in the medullary rays
- Transports ions from the lumen of the tubule to the interstitium via mainly active transport
- Reabsorption of other ions: Ca2+ and Mg2+
Describe the distal convuluted tubule
Very short-starts at the macula densa and ends at connecting tubule
- Less numerous profile in sections as it is 1/3 the length of PCT
- Simple cuboidal epithelium
- Smaller cuboidal epithelium
- Less acidophilic cytoplasm
- Fewer and shorter microvilli however extensive basal folds
- Apically placed nucleus
What are the functions of the distal convuluted tubule?
- Reabsorption
- Na+ and secretion of K+
- bicarbonate and secretion of H+
- Secretion of ammonium
- Parathyroid regulated Ca2+ reabsorption
- Relatively impermeable to water
- Highest Na+/K+ ATPase activity
What are macula densa?
-Modified cells of the distal straight tubule
Located at the vascular pole -forms part of the juxtaglomerular apparatus which regulates blood pressure
- Narrower and taller cells
- Senses chambers in Na+ concentration within the lumen of the distal tubule and sends signals to the juxtaglomerular cells (Modified smooth muscle cells) located in the afferent arteriole
What features help identify DCT?
Ratio off PCT to DCT (6:1)
- Epithelial cells are smaller
- Smaller inter- nuclear distance (smaller profiles)
- Clearer lumen
- Relaatively basophilic cytoplasm (lesser mitochondria)
How does the kidney help regulate blood pressure?
Juxtaglomerular apparatus components
- Macula densa(osmoreceptors)
- Extra Glomerular mesangial cells (Lacis/ Polkissen cells)
- Juxtaglomerular cells(JG cells)
I. Modified smooth muscle cells of afferent arteriole
II. Produce renin—> cleaves angiotensinogen to angiotensin I
Where are angiotensin I converted to angiotensin II?
Angiotensin I converted to angiotensin II (pulmonary endothelial cells)
- potent vasoconstrictor
- stimulates aldosterone secretion from adrenal cortex
- aldosterone stimulates reabsorption of Na+ and secretion of K+ by connecting tubules and collecting ducts
