Kidney Flashcards
What is the average size of the kidney?
6cm in diameter
3cm thick
11cm high
What is the structure of the kidney?
large bean shaped organs
Lateral-One side is concave
Medial-One side is convex- inside convex there is vertical cleft- which is renal hilum
What is the structure of the kidney?
large bean shaped organs
Lateral-One side is concave
Medial-One side is convex- inside convex there is vertical cleft- which is renal hilum
Adrenal gland sits on top- and it has its own blood supply
What is a renal hilum?
All blood vessels go into kidney and ureter comes out
-Ureter and renal blood join the kidney here (at hilium)
What are the function of the kidney?
Homeostasis
1- osmoregulation- control of total body water volume
2-electrolyte balance- balance osmolality- concentration of different solutes (urea,salt ) in blood - regulate the electrolyte balance in body
3-Acid-base- regulate pH of blood- balance- acidic or basic- urea
4- Toxic wastes- exit point- filter blood plasma (-200L/day) supplied by renal artery- processes detoxified blood
no alternative means of excreting metabolic waste; urea, uric acid or creatine
-drugs
-other toxins
5-Produces erthropoiten and renin- regulate blood cell production and blood pressure- hormones secreted by kidney
6- Convert VitD to active form- use around body
7- Starvation- metabolism and gluconeogenesis- kidney help
What do the first 4 functions relate to?
the urinary system
What does the urinary system do?
Kidney- filter blood and take out urine
Urine goes into ureter
urine stored in bladder
expelled through urthera
What is the main exit from the kidney?
urine
By:
-regulating blood volume and salt conc and waste disposl- by excreting urine
What is urine?
filtrate from blood plasma
What is normal urine?
differs from filtered blood plasma
What is the urine made from?
-91-96% water and rest dissolved solutes- higher concentration than plasma including:
-Salt (na and cl), other electrolytes (K, H+, HCO3-)
-Slightly acidic- pH 5.5-6
-No cells nutrients or plasma proteins
-Urea and uric acid (nitrogenous waste from a.a and nucleic acid metabolism)
-creatinine- (muscle waste from ATP metabolism)
-
How much urine do average person produce in a day?
average 0.6L- 2.6L
-6-8 urinations per day - 350ml- capacity of bladder
What are the 3 key regions in the kidney?describe.
1- Cortex- outer region- light colour
2- Medulla- dark reddish brown triangle- RENAL pyramids - separated with renal columns-made of cortex- is the gap in between medulla
Stripped- high density of blood vessels/bundles of capillaries and nephrons with collecting tubes- add to striped appearance
3- Pelvis- funnel shaped tube- with continuous ureter
-fed by calyces- filter in a larger tube of pelvis
-ultimately fed down to ureter
-blood vessels coming in- renal hilus
What is a the functional unit where filtation occurs?
Nephron- regulation of urine and blood consitiunents
What are the different regions of the nephron?
- Bowmans capsule- primary point of filtration- sits in the cortex of the kidney- blood filtered plasma (runs through all tubes)
- Proximal convoluted tubule- PCT- dives down into medulla forming Loop of Henle
- Loop OF Henle- has ascending and descending limb- in medulla
- This tube comes back to cortex- DCT- goes into medulla
- Forming collecting duct- goes all the way through medulla- it has an opening straight into minor calycx.
What is the nephron- blood relations?
1- blood comes through Renal artery and crosses pelvis/calyces
2- Turns into interlobar arteries which ascend renal columns
3-Turns into afferent arterioles- smaller blood vessels- they turn into glomerular capillaries
4-Glomerular capillaries- the filtration point- network of capillaries that sit inside a cup of the bowman capsule of the nephron
5- Exits efferent arteriole- drain glomeruli
6-Peritubular capillaries- stay in cortex- wrap around PCT and DCT reclaim reabsorbed substances- drain
7-Vasa Recta- blood vessels which around loop of henle and collecing tube for water/ion exchange
What can each collecting do?
can be fed by more than one nephron
What are the 3 main functions of kidney:
1- Filtration- between the glomerulus/bowmans capsule- renal corpuscle- fluid coming from the blood plasma to the bowmans capsule
2-Reabsorption- by the PCT and loop of henle- of water and nutrients or excretion of more water in urine
3-Secretion- by the DCT
How is plasma filtered?
1- Blood enters glomerulus under pressure- due to afferent arterioles( feed into glomerulus) has a larger diameter than efferent arteriole- this means all of the blood under these capillaries are under higher pressure- essential which forces the plasma out
2-Glomerular endothelial wall is fenesrated- have little pores- plasma forced through the pores
3-Bowmans capsule- podocytes wrap around glomerular capillaries- between podocytes are gaps
4- Plasma passes through ‘filtration’ slits (gaps between podocytes) between adjoining podocytes- to enter lumen bowmans capsule and then the PCT.
What does it mean when filtration is in discriminant?
It results in 2 problems:
1) blood plasma all small molecules (less than 8nm= plasma membrane/ proteins) enter bowman capsule, including nutrients like amino acids, peptides, glucose, vitamins etc are on the route from getting excreted from the body (which is not what you want)
2) 100 times more plasma is filtered each day than the volume of urine that the body needs to produce.
What is the solution to the filtration being in discriminant?
: the rest of the nephron is mainly involved in reclaiming- 98% of the initial filtrate are absorbed back from bowman’s capsule back in the body (nutrients and water) - which done by the PCT, Loop of henle, DCT and collecting duct.
What is the PCT?
the most active reabsorbers of the filtrate
What do the PCT do?
Have specialised epithelial cells that start the process- which also go down Loop of Henle- They have:
- numerous microvilli- on the lumenal surface -high s.a for absorption
- Associated Mitochondria-do lots of active transport- high conc of mitochondria
- Active absorption of nutrients and ions
- WATER flows passively
- mitochondria also basal region for active transport to peritubular capillaries
What is the Loop of henle?
concentration of solutes in the blood is about 300- which is coming out the PCT
- Water is getting reabsorbed in by the descending loop cells (which are impermeable to ions) concentrating the filtrate
- Salt is reabsorbed by ascending loop cells (which are impermeable to water) diluting the filtrate.- active transport of salts
What is osmolality?
The number of solute particles in 1L of water- measure of concentration
What is the osmolality?
blood plasma and the PCT filtrate are the same - average is 300milliOsmols (mOsm)
What is normal urine?
- But normal urine is hyperosmotic- 500-700mOsm
- want more urine to be concentrated due to higher waste- want less water and more wastes such as urea.
How does normal urine happen?
The counter current exchange
What is the counter current exchange?
- difference in osmolarity gradients in the 2 loops of henle
- This drives (driving force) a NaCl pumps on the ascending limp- actively transferring salts across but not water
- left with solution
- reclaim water via collecting duct
- The filtrate leaving Henle’s Loop & entering the DCT is normally ‘hypo-osmotic’ (100 mOsm), but is concentrated later in the Collecting Ducts via counter-current exchange with hyper-osmotic interstitial fluid in the surrounding medulla
Where do these salts and water go back to?
-Salts and water re-enter the blood supply through the vasa recta
What is the balancing act?
The functional significance -Balancing act in kidney - Water ingestion/ 3L/ day Fluid intake- 1.5 In food-- 1.3 From food metabolism- 0.2- condensation reactions
-Water excretion 3L/Day urine- 2.0 evaporation from lungs, skin- 0.8 with faeces- 0.2 sweat-0.1
What are the variables for water ingestion?
High/low intakes
High salt- causes the body to retain the water in order to counter balance as you dont want salt levels to accumulate in body
What are the variables for water excretion?
Heat, exercise
Illness, diarrohea
What are the extremes of urine?
- They are either extremely dilute or concentrated
- This is how we regulate- depends on how much water or salt you need to get rid of
What happens when you have dilute urine?
- Excess water intake
- Urine osmolarity needs to be low= 100mOsm
- Maintain low - so no re- absorption of water from collecting duct
- Urine volume needs to be high = 20 L/day
- no change to filtrate after Henle’s Loop
- hence secrete more water
What happens when you have concentrated urine?
- effect of excess salt intake
- Urine osmolarity needs to be high= 1200mOsm
- Urine volume needs to be low = 0.5L
- Mechanism- more water must be reabsorbed from the filtrate in the collecting ducts after henles loop
- secrete salts if excess conc
How is the urine regulated?
DCT cells and Urine conc
-In the DCT- which wraps around glomerular- makes contact with bowmans capsule
.- have sensory cells which monitor conc of NaCL in the blood - Macula Densa cells
-Juxtaglomerular cells- smooth muscle cells in afferent and efferent arterioles - which monitor pressue - water volume of blood, or salt conc- can stimulate hormonal response
Results: decrease in pressure or decrease in [NaCl] leads to Renin secretion from Juxtaglomerular cells. This regulates glomerular filtration rate.
What is the effect of renin when released by juxta-glomerular cells?
Renin released- FROM KIDNEY
- Renin is an enzyme changes anginostenin which changes it into a active form of antiogenstenin 1
- ACE- changes into angiotensisn 2- can also be secreted from lungs too
- Angiotensisin 2 - can be picked by adrenal, pituitary gland- act as a hormone
- This can change neural activity and direct effect of arterioles in the body e.g. effect on pituitary gland is to increase ADH secretion and that affects water absorption in renal collecting duct.
How can kidney failure occur?
infection, trauma, poisons (lead, solvents)
Symptoms: (severe)
oedema (water & salt retention)
cardiac arhythmia (excess K+)
azotemia (acidic blood pH)
convulsions, coma & death (brain cells swell)
Treatment: (unpleasant)
haemodialysis (artificial kidney)
organ transplant (UK waiting list 7000; 2.5-3yrs)
What is haemo- dialysis?
Blood plasma cleansed via permeable tubes
Heparin given to prevent clotting
Session lasts 4-8 hours
Need 3-4 per week
Problems = haemorrhage, infection, thrombosis
