This is what I have summarized about renal physiology, for PASSING EOS. If you’re aiming to score, this is useless for you.
· Pair of bean-shaped organs
o Retroperitoneal space
o Either side of vertebra
o Level of lower thoracic and upper lumber vertebrae
o Right kidney
§ Slightly lower than left
§ Because of liver
o Weighs about 120-170g each
o Measures 12x6x3 cm
o There is 2 regions if you cut coronally
§ Cortex
· Outer pale region
§ Medulla
· Inner dark region
o The structures you can appreciate grossly
§ Pyramids
· Conical structures in medulla
· Base of each pyramid situated at corticomedullary junction
· Apex extend to hilum of kidney
§ Hilum of kidney
· Region where all the arteries, veins and nerves, renal pelvis enter
· In the medial aspect - concave part
§ Renal pelvis
· Communicates with a flattened space withing the kidney called renal sinus
§ Renal sinus
· Renal pelvis branches into major and minor cayces to collect the urine
§ Calyx
· The congregation (collection) of collecting ducts.
§ Renal papilla
· Region where you would see the collecting ducts and loop of henle
· Blood is delivered to each kidney from main renal artery branching from aorta at level of L1
· Renal artery enter hilum and usually divides into 2 main segmental branches
o Those are further divided into several lobar arteries supplying the upper, mid, and lower region of kidney.
§ These vessels branch further as they enter the renal parenchyma and create interlobar arteries that course toward the renal cortex along lateral margin of medullary pyramids
§ At the corticomedullary junction, these smaller arteries provide perpendicular branches that continue in an archlike manner, appropriately named Arcuate arteries.
§ Interlobular arteries arise from arcuate arteries, branch radially thru cortex.
§ Glomerular capillaries receive blood thru afferent arterioles that originate from these interlobular arteries.
§ Efferent arterioles leaves glomerular capillary bed and supplies a network of vessels that surround the tubular structures called vasa recta in the juxtamedullary glomeruli system. (there are 2 types of nephrons, juxtamedullary and cortical)
· Summary of blood flow in the renal system-
o Renal artery
§ Interlobar arteries
· Arcuate arteries
o Interlobular arteries
§ Afferent arterioles
· Glomerulus
o Efferent arterioles
§ Vasa recta
bladder
· In adults the bladder is a pelvic organ. It lies behind the pubis and is covered superiorly by peritoneum. It acts as a receptacle for urine and has a capacity of approximately 500 mL.
· Structure:
o the bladder is pyramidal in shape.
o The apex of the pyramid points forwards and from it a fibrous cord, the urachus, passes upwards to the umbilicus as the median umbilical ligament.
o The base (posterior surface) is triangular.
o In the male, the seminal vesicles lie on the outer posterior surface of the bladder and are separated by the vas deferens.
o The rectum lies behind.
o In the female, the vagina intervenes between the bladder and rectum.
o The inferolateral surfaces are related inferiorly to the pelvic floor and anteriorly to the retropubic fat pad and pubic bones.
o The bladder neck fuses with the prostate in the male whereas it lies directly on the pelvic fascia in the female. The pelvic fascia is thickened in the form of the puboprostatic ligaments (male) and pubovesical ligaments to hold the bladder neck in position.
o The mucous membrane of the bladder is thrown into folds when the bladder is empty with the exception of the membrane overlying the base (termed the trigone) which is smooth. The superior angles of the trigone mark the openings of the ureteric orifices.
o A muscular elevation, the interureteric ridge, runs between the ureteric orifices.
o The inferior angle of the trigone corresponds to the internal urethral meatus.
o The muscle coat of the bladder is composed of a triple layer of trabeculated smooth muscle known as the detrusor (muscle).
o The detrusor is thickened at the bladder neck to form the sphincter vesicae.
· Blood supply:
o is from the superior and inferior vesical arteries (branches of the internal iliac artery).
o The vesical veins coalesce around the bladder to form a plexus that drains into the internal iliac
o vein.
· Lymph drainage:
o is to the para-aortic nodes.
· Nerve supply:
o motor input to the detrusor muscle is from efferent parasympathetic fibres from S2–4.
o Fibres from the same source convey inhibitory fibres to the internal sphincter so that co-ordinated micturition can occur.
o Conversely, sympathetic efferent fibres inhibit the detrusor and stimulate the sphincter.
· General characteristic
o Basic structural functional unit of kidney is the nephron.
o Each kidney has approx. 1 million nephrons
o Each nephron is composed of 2 major component
§ Filtering element (renal corpuscle)
· Bowman’s capsule
· Glomerulus
§ Tubules
· Proximal Convoluted Tubule
· Loop of henle
o Descending
o Ascending
· Distal convoluted Tubule
· Collecting duct
o Nephrons are classified on basis of whether they have a short or long loop of henle.
§ The short-looped nephrons usually originate from the superficial and mid-cortical areas, called cortical nephrons
§ The long-looped nephrons originate from the juxtamedullary regions, and their loops of henle extend into the inner medulla.
· Unique network of capilliaries suspended between the afferent and efferent arterioles
· Enclosed within an epithelial structure called the bowman’s capsule
· The capillaries are arranged into lobular structures calle glomerular tufts
· Lined by thin layer of endothelial cells
· The core consists of mesangium -
o consists of mesangial cell and surrounding mesangial matrix
· Other components
o Glomerular besement membrane
o Visceral and parietal epithelial cells
o Vascular pole
o Urinary pole
· The visceral epithelial cells (podocytes)
o Highly specialized pericytes
o Complex cytoarchitecture with prominent surface of foot processes
o Between those foot processes are slit diaphragm
§ Most important barrier in the filtration system
§ Hereditary conditions of nephrotic $ are associated with mutation in genes which makes products which establish this structure
· Nephrin
· Podocin
· A-actinin 4
· CD2 assoc. protein
§ Causing congenital focal glomerular sclerosis in 3rd and 4th decade of life
· Thin layer of fenestrated endothelial cells lines the glomerular capillary lumen
· These fenestrae are larger than most in body
o Responsible for the high ultra-filtration coefficient of glomerulus
· Polyanionic glycoprotein coat enables makes it more impermeable to negatively charged molecules e.g. albumin
· Layer of hydrated gel composed of glycoproteins containing interwoven collagen fibres (type4 and 5)
· Glomerular capillaries course along structure called mesangium which is embedded mesangial matrix
· Mesangial cells have structural characteristics of smooth muscles and contain actin, myosin, and a-actin.
· Cells attached thru cytoplasmic projections.
· Tightly adherent to every glomerulus at site between entry and exit of arterioles
· Plaque of DCT cells called macula densa
o Forms the juxtaglomerular apparatus
o This region control NaCl transport
o Through pocess of tubuloglomerular feedback
o These cells are richly innervated by sympathetic neuron
· 1/5 of cardiac output perfuse kidneys
· Highest blood flow by weight of any organ in body
· Ultrafiltrate of blood is formed in glomerulus driven by starling forces
· The unusually high hydraulic permeability of filtration barrier, high ultrafiltration pressure achieved by the afferent and efferent arteriole size difference and increased surface area of filtration area all contribute to GFR
· Normal GFR dependant on;
o Size
o Age
o Diet
o Physiologic state
o Gender
o Pregnancy
· Serum creatinine used for measure of GFR
· GFR decreased in
o Chronic renal disease
o Circulatory collapse
o Glomerulonephritis
o Obstruction of urine
o Heart failure
· Glomerular filtrate is modified as it courses thru the nephron to become the urine.
· Net absorption of
o Na
o Cl
o H2O
o HCO3
o Glucose
o Amino acids
o Phosphates
o Ca
o Mg
o Uric acid
· Excretion of
o H
o NH4
o Organic acids
o Organic bases
· Excretion AND reabsorption of
o K
o Urea
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