FUNCTIONS
look at kidney slide
- Regulation and maintenance of water and
electrolyte homeostasis.
* Input = Output
* Ureters, bladder and urethra - form the storage and outflow tract. - Regulation of acid-base homeostasis.
- Excretion of excess water and electrolytes, toxic
metabolic waste products (urea and creatinine). - Osmoregulation all body fluids in equilibrium
- Production of RENIN for the maintenance of
normal blood pressure.
6.FILTER BLOOD
renal artery supplies the kidney with unfiltered blood
renal vein carries filtered blood
Primary and
accessory organs:
- 2 kidneys - nephron is the functional unit
- Renal vessels
- 2 ureters
- Urinary bladder
- Urethra
- Adrenal glands sit on the kidney
KIDNEYS
-* Bean-shaped
*right sits by the liver is smaller and lower than left
Coverings:
Fibrous Renal capsule - protection DICT
Outer: fibroblasts and collagen
Inner: myofibroblasts.
2.Middle Perinephric fat capsule- Cushions the kidneys
- Renal or Gerota’s fascia -Helps keep the kidney in its correct location DICT
Hilum
* Concave (indented) depression where blood vessels and ureter enter and leave the kidney.
Renal cortex— outer region darker
* Extensions of cortex and renal columns - extend inward and separate the pyramids
Renal medulla— inside the cortex
* Triangular regions of tissue -Renal pyramids.
* Renal papillae - each papilla is surrounded by a branch of renal pelvis – Calyx.
Renal Calyx - collects urine
* Cup-shaped structures that funnel urine towards the renal pelvis.
Renal pelvis - terminal end
* Collection of calyces, surrounded by renal sinuses that merge to become the ureters
- Pelvicalyceal system (PCS) –where the calyces and it terminates at the pelvis
- Renal sinus – space between the branches of
the pelvicalyceal system filled with adipose
tissue. fatty supportive tissue
NEPHRONS
-blood filtration and urine formation
two types of nephrons:
Cortical nephron- Located in the cortex.- most nephrons.
Juxtamedullary nephron at the boundary of the cortex and medulla.
TWO MAJOR COMPONENTS OF THE NEPHRON:
Renal corpuscle - filtration of plasma.
Made up of:
* Bowman’s capsule – simple squamous cells o
* Glomerulus - anastomosing capillaries.
* Spaces – Mesangium containing mesangial cells
* On the capillaries – Podocytes.
* Bowman’s space – between visceral and parietal layer contains the ultrafiltrate that will get absorbed
Renal tubules:
* Selective re-absorption of water, inorganic ions, and molecules from glomerular ultra filtrate (GUF).
* Structures: Proximal convoluted tubules, The loop of Henle (medulla), Distal convoluted tubules and Collecting tubule (medulla)
Flow of the Glomerular Ultrafiltrate
(GUF)
- Blood enters afferent arterial, into the renal
corpuscle for filtration. - Cleansed blood leaves through efferent arterial and the ultrafiltrate will go through the renal tubules for selective reabsorption.
- Starting at the proximal convoluted tubules for (PCT) → into the descending thick/thin loop of Henle → back up through the ascending thin/thick loop of Henle → distal convoluted tubules (DCT) →
- Urine drains into collecting tubules → collecting ducts and merge to form the Ducts of Bellini.
- urine accumulates in the renal papillae and calyx (Pelvicalyceal system) where it gets discharged into the ureters.
histology of cortex and medulla
Cortex:
* Renal corpuscles found only in the cortex
Renal tubules:
* Proximal convoluted tubules
* Distal convoluted tubules
Medulla:
Renal tubules
* Loops of Henle
* Collecting tubules
* Collecting ducts
PARTS OF THE NEPHRON IN
THE RENAL CORTEX
Renal corpuscles consists of:
* Bowman’s capsule
* Glomerulus
* Bowman’s space
PCT – proximal convoluted tubules - Simple cuboidal with microvilli
DCT – distal convoluted tubules- Simple cuboidal
the arcuate artery demarcates the cortex from the medulla
RENAL CORPUSCLE:
BOWMAN’S CAPSULE made up of
Glomerular Ultrafiltrate GUF
Surrounds the Bowman’s space
Two layers:
* Parietal layer = Simple squamous- Continuous with the epithelium of the renal tubule
* Visceral layer = with podocytes the cover the capillaries
- Bowman’s space – space between the 2 layers
- Continuous with the lumen of a renal tubule
Glomerular Ultrafiltrate GUF
-the leftovers fluid after water and low MW bells are filtered from the plasma by the glomerular capillaries
-goes into a series of renal tubules to be absorbed
Filtration Barrier
-located between the capillary lumen and Bowmans capsule consists of:
Capillary Endothelium
Podocyte layer
Glomerular basement membrane
MESANGIUM
- Basement membrane-like material in between the
capillary loops in the glomerulus. - Located outside the capillary lumen but
surrounded by capillaries. - Supportive and phagocytic role (keeps the filter debris free).
- Made up of mesangial cells and mesangial matrix.
PODOCYTES
- large epithelial cells with a cell body and foot
processes (pedicels) - Rest on the capillaries and form the visceral
layer of the capsule - selective permeability of the glomerular filtration
barrier
- Urinary pole
- Vascular pole
Urinary pole - Entrance to the renal tubule (PCT) simple cub with microvilli
Vascular pole
* Where afferent arteriole enters, and efferent arteriole leaves the corpuscle.
* Afferent arteriole – supplies the glomerulus; larger diameter.
* Efferent arteriole – drains the glomerulus; smaller diameter.
THE RENAL TUBULES what do they do
- Selective reabsorption of water, ions and other
molecules from the GUF - extend from glomerular capsule and end at the collecting duct.
- Proximal convoluted tubule (PCT)
- Loop of Henle – thin - descend and thick ascend (LH)
- Distal convoluted tubules (DCT)
- Collecting tubule (CT)
- Collecting ducts (CD) → Duct of Bellini (DB)
Duct of Bellini terminates at the calyx and
eventually into the pelvis, ureter.
PROXIMAL CONVOLUTED TUBULE (PCT)
* Longest and most convoluted - more cyto and small lumer
* Reabsorption of ions and water of the GUF.
* Location: Renal cortex
* Epithelium: Simple cuboidal with microvilli.
DISTAL CONVOLUTED TUBULE (DCT) less cyto and larger lumen
* Continuation of the thick limb of the loop of Henle after its return to the renal cortex.
* Function: Reabsorption of sodium ions – body becomes less acidic.
* Location: Renal cortex
* Epithelium: Simple cuboidal.
JUXTAGLOMEULAR APPARATUS
(JGA)
- formed by the DCT and afferent arteriole
- Regulates blood pressure
- JGA cells secrete hormone for salt concentration, renin when BP drops
contains Macular densa
* Collection of specialized cells in the DCT (adjacent to JG cells)
* Cells are chemoreceptors for NaCl concentration in the tubule
LOOP OF HENLE (LH)
*generate high osmotic pressure
* Thin loops (descending and ascending) dip down into the medulla.
* Location: Renal medulla.
* Length of the loops vary according to location of the nephrons
* Short – cortical nephrons
* Long – juxtaglomerulary nephrons
- Epithelium:
- Thick loop of Henle – Simple cuboidal wider lumen
- Thin loop of Henle – Simple squamous
will see them close to the collecting tubules with higher cuboidal cells
COLLECTING TUBULES
→ COLLECTING DUCTS
- Normally impermeable to water BUT with ADH present, they become permeable to water. Collecting ducts are under control of ADH
This results in increased osmotic pressure and production of hypertonic urine with respect to plasma.
Function: the ultrafiltrate goes from distal tubule and empties into the collecting tubule and then a duct will run through the medullary pyramids and deliver into the calyces and renal pelvis.
Location: Renal medulla.
Epithelium: Simple (high) cuboidal or simple (low) columnar.
what are URETERS
- A tube that carries urine from the kidney to the urinary bladder.
- There are two ureters, one attached to each kidney.
- Muscular tube running from each kidney to urinary bladder (starts at renal pelvis and ends at urinary bladder).
*Storage and excretion
3 layers - has rugae for stretching and infoldings:
* Inner: mucosa * Epithelium – Transitional with dome shaped cells. The lumen is also known as Urothelium. Flat cells depending on state like when urine in passing through
* Lamina propria – LOCT
- Middle: muscularis- 3 layers of smooth muscles non striated involuntary (peristaltic movements)* Inner longitudinal, Middle circular * Outer longitudinal
- Outer: adventitia - LOCT
URINARY BLADDER
- Muscular, collapsible bag.
- Hollow organ behind the pubic bone and in front of the rectum.
- Females: anterior to vagina and below uterus.
- Males: rests on top of prostate.
- Three openings inside the bladder - Two for the ureters and one for the urethra.
Rugae: Infoldings in the epithelial wall for distension.
Mucosa: Epithelium – Transitional+ Submucosa*** Lamina propria – LOCT
Muscularis mucosa: Muscularis: 3 non-distinct detrusor muscles:
- Inner longitudinal
-Middle circular
- Outer longitudinal
- Adventitia: LOCT
URETHRA
- Fibromuscular tube that connects to the bladder
in order to empty urine out of the body.
Epithelium
* Proximal urethra – Transitional
* Middle urethra – Simple columnar
* Distal urethra – SSNK
Lamina propria: Highly vascular + Glandular
Muscularis (makes up the sphincter of the urinary
bladder) : Smooth muscles external urinal scpinter** + Skeletal muscles
Flow
aorta - renal artery - segmental - interlobar- arcuate- cortical radiate - Afferent arteriole -filtered in the glomerulus IN RENAL CORTEX - CLEAN BLOOD IN
efferent arteriole - peritubular capillaries- cortical radiate vein in the kidney- Arcuate-interlobar-renal vein - inferior vena cava to go back to the heart
