Anatomy and Physiology Flashcards
What is the Renal hilum
Passage of blood vessels, ureter, lymphatics and nerves into the kidney
What is the anatomical marking for the kidneys?
Tip of Left kidney: 11th rib
Tip of right kidney: 12th rib
How much of the resting cardiac output do the kidneys receive?
20-25%
Describe the changes in vasculature throughout the kidneys
Renal artery - segmental arteries - interlobar arteries - arcuate arteries - interlobular arteries - afferent arteriole - glomerular arteries - efferent arteriole - peritubular capillaries - interlobular veins - arcuate veins - interlobar veins - segmental veins - renal vein
What effect does sympathetic innervation have on the kidney?
Causes vasoconstriction
What is the Juxtaglomerular apparatus?
“next to glomerulus”
Made up of Juxtaglomerular cells (secrete renin). Macula Densa (part of DCT) and Extraglomerular
What common molecules are fully filtered in the glomerulus?
Water
Glucose
Urea
What is glomerular filtration dependent on?
glomerular blood hydrostatic pressure
capsular hydrostatic pressure
blood colloid osmotic pressure
where is glucose reabsorbed?
PCT
Where are amino acids reabsorbed?
PCT
Where would you find ENaC and what is its function?
- DCT
- Na/K pump on basolateral side causes a sodium concentration gradient, allowing the passage of Na out of the lumen and into principle cell. This creates a negative charge within the lumen, allowing for the passage of potassium and hydrogen through specific transporters
Describe the location and mechanism for calcium and magnesium reabsorption
- Na/K pump on basolateral side causes a sodium concentration gradient.
- NaK2Cl transporter in thick ascending limb allow for passage of Na and K into the principle cell, with 2Cl following due to electrochemical charge.
- K is recycled into the lumen due to concentration gradient, creating a highly positive charge within the lumen
- Calcium and magnesium then diffuse through cell junctions due to electrochemical gradient
How much NaCl is reabsorbed in the PCT?
70%
Why might a patient have glycosuria?
Hyperglycaemic condition deliver excess glucose through the glomerular filtration barrier, exceeding the capacity of the SGLUT2 cotransporters, meaning that glucose is excreted in urine.
What is secreted into the fluid?
waste
drugs (e.g. penicillin)
excess ions (e.g. K, NH4)
Describe the function and mechanism of the counter current exchange multiplier
It is a mechanism used to vary urine concentration, named due to the counter current of descending and ascending limbs of LoH
- Na and Cl pumped out of the thick ascending limb by NaK2Cl cotransporters, decreasing osmolality in the tubule (200) but increasing it in the medullary interstitial fluid (400)
- Water flows out of descending limb in order to match the osmolality of interstitial fluid (both 400)
- this process continues with the filtrate flowing round the loop, eventually resulting in a vertical concentration gradient down the interstitium and LoH
- This means that dilute urine is passed into the collecting duct which due to aquaporin and the increasing concentration of interstitium as you go down, water flows out, varying urine concentration
What is the maximum concentration of interstitium?
1200mosml/l
Explain the response of the kidney to lowered blood pressure
Decrease in blood pressure is detected by baroreceptors in aortic arch, carotid sinus and afferent arteriole, causign sympathetic constriction of afferent arteriole. This decreases blood flow to the glomerulus, stimulating the macula densa to cause renin production from the granular cells. Renin converts Angiotensinogen to angiotensin I which is converted to angiotensin II by ACE in lungs. Angiotensin II then has three mechanisms to increase blood flow:
- Efferent arteiole contriction - preserve waste excretion
- Increase Na and Cl reabsorption to preserve volume and increase water reabsoprtion
- Stimulates aldosterone production - increases Na and Cl reabsorption to increase water reabsoprtion and increase blood pressure
ADH production acts on collecting ducts by inserting aquaporin for increased water absorption to increase blood pressure
Explain the response of the kidney to raised blood pressure
stretch receptor in atria detect incresed blood pressure, causing release of ANP. This inhibits sodium and water reabsorption in PCT and suppresses ADH and aldosterone, resulting in excess water (diuresis) and sodium (naturesis) loss.
When is aldosterone produced and what does it do to kidney?
Produced due to angiotensin II (low BP) or hyperkalaemia
inserts ENaC into collecting duct and DCT to encourage Na and chloride reabsorption, and encourages Potassium excretion
Describe the mechanism of ADH action
High serum osmolality and hypotension causes the posterior pituitary to secrete ADH (made in hypothalamus). This binds to V2 receptors (vasopressin), inducing cAMP pathway, resulting in aquaporin II insertion on luminal side for water reabsorption which enters blood via aquaporin I on blood side
Describe the mechanism of action of PTH
Low serum calcium levels cause secretion of PTH which stimulates cells in DCT to reabsorb more calcium.
Also inhibits phosphate reabsorption in PCT, increasing excretion
What are the functions of the kidney?
“A WET BED”:
- Acid balance
- Wate Balance
- Electrolyte balance
- Toxin removal
- Blood pressure control
- Erythropoetin production
- D vitamin metabolism
Describe the vasculature of the kidneys
Arterial - Superior and inferior vesical arteries from internal iliac
Describe the different parts of the male urethra and their lengths
Prostatic - 3-4cm
Membranous - 1-2cm
Penile/Spongy - 15cm
What epithelial lines the bladder?
Transitional
How is the mucosa of the bladder arranged when it iss empty?
Ruggae
Describe the epithelial lining of the male urethra
Prostatic - transitional
Membranous - pseudostratified columnar
Penile - pseudostratified columnar into stratified squamous
Describe the make up of the external urethral sphincter
rhabdosphincter and peri-urethral striated muscle
Decsribe the process of micturition
- Stretch receptors in bladder wall send impulses via afferent nerves to ONUFs nucleus in the anterior horn of S2-4.
- This relays signals up spinal cord to Pontine Micturition Centre in the Pons which interacts with cerebrum, cortex, extrapyramidal system and brainstem to determien whether acceptable to urinate.
- If acceptable, no inhibitory signals are sent so the ONUFs nucleus send parasympathetc neurons to bladder for contraction.
- If inappropriate time, PMC has spino-bulbar-spinal reflex, inhibiting the parasympathetic neurones from ONUFs nucleus and also sending neurons to contract external urethral sphincter
Describe the process of bladder contraction
Ach binds to muscarinic receptors - M3 are the functionally important ones but there are more M2
Membrane depolarisation also
Both result in influx of Ca
