Kidney background Flashcards
Which embryological layer are the kidneys derived from?
Intermediate mesoderm
What is the cortex of the kidney?
Outer layer of kidney
What is the medulla of the kidney?
Inner layer of kidney
What is upper urinary tract?
Kidney and ureters
What is a lower respiratory tract?
Urinary bladder and urethra
What are the kidneys supported by?
Connective tissue
Anterior: renal fascia anterior posterior
Posterior: Fibrous capsule
What is the structural unit of the kidney?
Nephron
What are the majority of kidney nephrons?
Cortical nephrons where glomeruli is located in the cortex
What are the juxtamedullary nephrons?
Glomeruli of the nephron is located in cortex but very close to medulla. Loop of Henle penetrates deep into the medulla and has a greater effect at increasing the conc of the medulla.
What is the innervation of the kidney?
Aorticorenal ganglia- derivative of the coeliac ganglia. Sympathetic nervous system regulates kidney blood flow and renin release
What is the Loop of Henle?
What is the interstitium?
Tissue separating the Loop of Henle and the vasa recta
What is the role of the Bowman’s capsule?
Surrounds the capillary loops of the glomerulus to participate in blood filtration. It creates a urinary space for filtrate to pass through the nephron and enter the PCT.
What is the Bowman’s capsule formed of?
Parietal protective layer formed of simple squamous epithelia. Visceral layer formed of podocytes
What is the role of the parietal layer of the Bowman’s capsule?
Formed of simple squamous epithelia where fluid accumulates.
What is the role of the visceral layer of the Bowman’s capsule?
Composed of podocytes to prevent large molecules leaving the Bowman’s capsule. Podocytes contain glycocalyx to prevent this.
What is the PCT?
Portion of nephron responsible for the reabsorption of Na+, Cl-, K+, glucose, amino acids and urea.
What is the PCT composed of?
Cuboidal epithelia lined with microvilli for absorption and secretion. Rich in mitochondria for energy-dependent ion transfer.
What is the role of the collecting duct?
Reabsorption of water, Na+, Cl- and urea
What are the cells of the collecting duct?
Major cell type are the prinicipal cells for water and sodium balance via Na+/K+ ATPase channels controlled by aldosterone. Intercalated cells are a minor type in the collecting duct.
What are the intercalated cells?
Responsible for acid-base homeostasis via the HCO3-/CL- exchanger and H+ pump in the collecting duct
What is the kidney blood supply?
Afferent arterile is a branch of the renal artery.
Efferent arteriole becomes the vasa recta and peritubular arteries.
What are the vasa recta?
Run parallel to the medulla of the kidney, especially the loop of Henle and DCT
What are the glomerular capillaries?
Anastomosis formed from branches of the afferent arteriole. They are the only capillaries not surrounded by interstital tissue and form a barrier for plasma proteins to enter urine.
What are the features of the glomerular capillaries?
High pressure filtration because vessels are short and wide so there is little resistance. Passive diffusion occurs here via hydrostatic pressure
What type of cell makes up the endothelium of the kidneys?
Fenestrated endothelial cells
What are the peritubular capillaries?
Blood vessels which run alongside the cortex of the kidney
Autoregulation
Adjustment of blood flow to organs depending on immediate requirements. In the kidneys, this is to maintain GFR when BP changes from 80-180
What is GFR?
Amount of blood filtered in the glomerulus
How does arterial blood pressure affect autoregulation of the kidney?
Causes changes in the renal arterial constriction and GFR to prevent renal injury to the glomeruli.
Below 80: BP is low so vasodilation occurs
Above 80: BP increase so vasoconstriction gradually increases
What are the mechanisms of autoregulation?
1)Myogenic mechanism
2)Tuberoglomerular mechanism
What is myogenic mechanism?
Response of smooth muscle mainly in the afferent arterioles and minorly the efferent arterioles for
vasoconstriction: decreased glomerulus blood flow and filtration
vasodilation: increased glomerulus blood flow and filtration
What causes decreased renal blood flow?
Hypertension
-> cholesterol, diabetes, smoking
What is the juxtaglomerular apparatus?
Portion of the DCT close to the glomerulus consisting of macula densa cells. These cells have chemoreceptors for Na+ and Cl- to detect GFR filtration rate.
What is the tuberoglomerular mechanism?
Macula densa of JGA detects Na+ and CL- and releases chemicals to induce changes to the smooth muscle in the glomerular arteries to affect GFR.
Tuberoglomerular mechanism- high Na+ and Cl-
Macula densa releases vasoconstrictor chemical ATP or adenosine to reduce filtration in the glomerulus
Tuberoglomerular mechanism- low Na+ and Cl-
Inhibits ATP release and increases renin release.
RAAS system
Drop in BP induces renin release.
Angiotensinogen is produced from liver, cleaved -> angiotensin 1 by renin.
Angiotensin 1 -> Angiotensin 2 by ACE which occurs in the lungs.
Angiotensin 2 binds to adrenal gland for aldosterone release.
Aldosterone acts on collecting ducts for insertion of aquaporin channels.
How do ion levels increase renin release?
Decrease in Na+ due to reduced reabsorption into blood
or
Increase in K+ due to reduced secretion into kidney
This occurs due to low GFR and BP
How is renal function assessed?
Renal clearance (ml/min) which is the volume of plasma when completely stripped of a substance by the kidney, which is determined by GFR