kidney structure and function Flashcards by daisy cunningham

name the urinary system components

2 kidneys (left and right) & 2 ureters (left and right),
urinary bladder & urethra

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define Nephrology

scientific study of anatomy, physiology & pathology of kidney

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define urology

branch of medicine dealing with male & female urinary systems & male reproductive system.

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what are the kidney functions

regulation of blood iron composition

maintenance of blood osmolarity

regulation of blood volume

Regulation of blood pressure

regulation of blood PH

release of hormones

regulation of blood glucose levels

secretion of waste and foreign substances

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explain kidneys regulation of blood iron composition

Na+, K+, Ca2+, Cl-, [HPO4]2-

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explain kidneys maintenance of blood osmolarity

by separately regulating loss of water & solutes in urine, maintains 290mOsm/litre

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explain kidneys regulation of blood volume

by conserving or eliminating water

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explain kidneys regulation of blood pressure

Adjusting blood volume:
- Reduced blood volume = reduced blood pressure

Renin secretion:
- activates renin-angiotensin pathway
——–> Increase vasoconstriction & blood volume = increased blood pressure

Adjusts renal resistance:
- encountered by blood flowing through kidneys which in turn affects systemic vascular resistance
——-> Increased renal resistance = increased blood pressure.

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explain the Renin-Angiotensin Pathway

for angiotensin II formation

liver produces angiotensinogen, which goes into blood stream with renin from kidney to produce angiotensin I. it then gets angiotensin converting enzyme from lung capillaries to form angiotensin II. which goes on to:
- vasoconstriction
- increased aldosterone secretion
- increased ADH secretion
- increased thirst

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explain kidneys in regulation of blood pressure

excrete variable amount H+ into urine & conserve bicarbonate which buffers H+

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explain kidneys in release of hormones

calcitriol
- regulate calcium homeostasis by increase absorption from foods in GI

erythropoietin
- stimulates RBC production

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explain kidneys in regulation of blood glucose level

deaminate glutamine, use it for synthesising new glucose

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explain kidneys in secretion of waste and foreign substances

in urine, due to body metabolism:

ammonia & urea
- from deamination of amino acids

bilirubin
- from catabolism of Hb

creatinine
- from breakdown of creatinine phosphate in muscles

uric acid
- from catabolism of nucleic acids

drugs & environmental toxins

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wheres the kidneys found in body

paired just above the waist

At concave side:
all blood & lymphatic vessels, nerves & ureter enter/leave by the renal hilum

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what 3 layers pf tissue are the kidneys surrounded by

renal capsule - transparent

adipose capsule - fat pad

renal fascia - connective tissue, attaches to posterior abdominal wall

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name 2 distinct regions of kidneys internal anatomy

renal cortex
renal medulla

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explain kidneys renal cortex

outer, smooth, reddish

the portions that extend between renal pyramids = renal columns

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explain kidneys renal medulla

inner, reddish-brown

consists of 8-18 cone-shaped renal pyramids; apex (renal papilla) points to centre

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what is the kidneys renal parenchyma

functional portion of kidney

composed of renal cortex + renal pyramids

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explain kidneys nephrons

Functional unit of the kidney

within parenchyma, ~1 million microscopic units.

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explain the travel of urine

urine is formed in nephron

then goes to:

papillary ducts = collecting ducts (several hundred)

then to:

minor (n=8-18) —-> major (2-3) calyces (cups)
(1 minor receives from ducts of 1 papilla)

then to:

renal pelvis (large single cavity)

then to:

ureter

then to:

urinary bladder

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name the 2 parts to the nephron

renal corpuscle

renal tubule

explain the nephrons renal corpuscle

(filters plasma)

Glomerulus:
- mass of capillary loops

Bowman’s Capsule:
- glomerular capsule surrounds glomerulus

explain the nephrons renal tubule

(into which filtered fluid passes)

proximal convoluted:
attached to Bowman’s capsule
Loop of Henle:
descending, hairpin, ascending
distal convoluted tubule

name the 2 positions of nephrons and what % of nephrons are in these types

cortical: 80-85% juxtamedullary: 15-20%

the renal corpuscles lie where in cortical and juxtamedullary positions of nephrons

cortical: Outer portion of renal cortex JUXTAMEDULLARY: Deep in cortex, close to medulla

explain loops of henle in the cortical and juxtamedullary positions of nephron

cortical: Short, mainly in cortex, slightly penetrate medulla juxtamedullary: Long, extend deep into medulla

explain the different blood supply to loops in the cortical and juxtamedullary positions of nephrons

cortical: From peritubular capillaries arising from efferent arterioles juxtamedullary: From peritubular capillaries & vasa recta arising from efferent arterioles

explain the different ascending loop limbs in cortical and juxtamedullary positions of nephrons

cortical: Thick only juxtamedullary: thin, then thick

what do the thick & thin segments of ascending limb loop actually refer to

height of epithelium and not the diameter of the lumen.

do kidneys have blood vessels and why

Abundantly supplied with blood vessels removes waste from blood & regulates its volume & composition

describe kidneys resting cardiac output

Although kidneys <0.5% body mass, receive 20-25% resting cardiac output via L + R renal arteries

what is adult renal blood flow in L/min

1.2 L/min.

summarise the path of blood flow through the kidney

from renal artery to arterioles to glomerular capillaries to efferent arterioles to peritubular capillaries to veins i.e., large to small arteries to small to large veins.

describe the looping pattern of vasa recta

it loops around the efferent arterioles, one side is ascending vasa recta (blue coloured) and one side is descending vasa recta (red coloured)

what are the 2 components of the renal corpuscle

Bowman’s capsule glomerulus

explain the SEM of renal blood vessels

Several glomeruli & other blood vessels in kidney High Power SEM of a single glomerulus (in a renal corpuscle)

what cells forms the entire wall of the glomerular capsule, renal tubule & ducts

a single layer of epithelial cells

Although epithelial cells forms the entire wall of the glomerular capsule, renal tubule & ducts, each part has what?

distinctive histological features that reflects its particular function

explain the Glomerular Capsule outer and inner layers

Outer parietal layer wall of simple squamous epithelium Inner visceral layer of specialised simple squamous epithelial cells = podocytes

what do podocytes do

wrap around the glomerular capillaries

pedicles allow what

filtration

explain Podocytes structure and function

have foot-like projections (pedicels) to cover capillaries Allow filtration slits (gaps) to be formed

capillaries are......

fenestrated

what make up the filtration membrane

Podocytes and fenestrated capillaries the membrane is 0.1mm thick

explain the filtration membrane

Fluid filtered from the capillaries (passed through basement membrane) passes filtration slits to enter the capsular (Bowman’s) space [between the 2 layers of the capsule]

what passes from blood to capsular space?

To space (if molecule <6nm diameter): H2O Glucose Vitamins Amino acids Very small plasma proteins Urea Ammonia Ions

what doesn't pass from blood to capsular space and so stays in blood

Albumen (7.1nm) Plasma proteins Platelets RBC & WB

describe the Renal Tubule & Collecting Duct histology

Prominent brush border of microvilli in proximal convoluted tubule cells, to increase surface area for reabsorption & secretion in a microscopic image: - the proximal convoluted tubule, does not have a clear centre due to presence of microvilli. Whereas distal convoluted tubule has no microvilli and so can see a clear, white centre of the tubule. - Black dots: = renal corpuscle - Blue & white dots = distal convoluted tubule - Red & yellow dots = proximal convoluted tubule.

explain the Juxtaglomerular Apparatus (JGA)

In each nephron, final portion of ascending limb (columnar & crowded = macula densa) makes intimate contact with afferent arteriole (modified SMC = juxtaglomerular cells) serving that renal corpuscle Together called JGA Secretes renin (JG cells) (regulates BP within kidneys)

the Last portion of distal collecting duct has what 2 cells types

principal cells intercalated cells

explain the Last portion of distal collecting ducts principal cells

most of the cells are these theyre Receptors for ADH & aldosterone

explain the Last portion of distal collecting ducts intercalated cells

fewer of the cells are these theyre Apical microvilli & many mitochondria Play role in haemostasis of blood pH

Drain to large papillary ducts are lines by what cells

simple columnar epithelial cells.