Renal Anatomy PDF

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Summary

Overview of renal anatomy....

Description

Renal Anatomy Kidney: ● Bean shaped paired organ found in retroperitoneal position. ● Between T12 and L3. ● Left kidney is superior, longer, more slender and closer to the midline when compared to the right kidney. ● Upper pole is nearer the midline than the lower. ● The right lies lower than the left because of the liver. Relationships of the right kidney: ● Superior pole: ○ Bare - covered by right suprarenal gland. ● Anterior surface - MEDIALLY: ○ Bare - covered by descending part of duodenum. ● Anterior surface at INFERIOR pole - MEDIALLY: ○ Associated with peritoneal loops of small intestine. ● Anterior surface at INFERIOR pole - LATERALLY: ○ Associated with right colic flexure. ● Anterior surface - SUPERIOR: ○ Covered by peritoneum and placed against right lobe of liver. Relationships of left kidney: ● Superior pole - MEDIALLY: ○ Bare - Left suprarenal gland. ● Superior pole - rest of ANTERIOR: ○ Stomach (medially) and spleen (laterally). ● LATERAL aspect of ANTERIOR surface: ○ Bare - Left colic flexure (superiorly) and descending colon (inferiorly). ● INFERIOR pole: ○ Covered by intraperitoneal jejunum. ● MIDDLE part of kidney: ○ Bare - Covered by retroperitoneal pancreas. Muscle relations to posterior of kidneys (medially to laterally): Psoas major Quadratus lumborum Transversus abdominis Costodiaphragmatic recesses also extend posterior to kidneys.

External anatomy of the kidney:

● Anterior and posterior surfaces of the kidney are covered by a fibrous capsule - renal capsule. ● Renal capsule is a smooth transparent sheet of dense irregular connective tissue continuous with outer layer of ureter. ● Renal capsule is surrounded by perinephric fat - protects kidney from trauma and holds it in place. ○ Perinephric space is located in the retroperitoneum between anterior pararenal space (APS) and posterior pararenal space (PPS). ○ PNS is bound by the Gerota’s fascia anteriorly and Zuckerkandl’s fascia posteriorly. ○ PNS contains kidneys, adrenal glands, arteries, veins and lymphatics. ● Renal fascia - layer of dense irregular CT that anchors the kidney and its surrounding structures of the abdominal cavity. ○ Gerota’s + Zuckerkandl’s fascia. ○ Fuse laterally to form lateral conal fascia.

● Medial indentation of the kidney occupied by renal hilum. ● Renal hilum is continuous with renal sinus. ● Renal sinus - cavity within the kidney that contains fat and hilar tubular structures.

● Hilum of kidney - from anterior to posterior: ○ Renal vein

○ Renal artery ○ Pelvis of ureter Internal anatomy of the kidney: ● Parenchyma - functional portion of the kidney with millions of nephrons. ● Renal cortex - pale band of tissue at periphery of sectioned kidney. ○ Subdivided into cortical and juxtamedullary zones. ● Extensions of renal cortex between the renal pyramids are renal columns. ● Renal medulla - composed of the renal pyramids. ○ BASE of pyramids is towards renal cortex. ○ APEX of pyramids towards renal sinus. ● Renal lobe - renal pyramid + overlying area of cortex + half of each adjacent renal column. ● Renal papilla - apex of renal pyramid. ● Minor calyx - cup-like structure where urine drains from renal papilla - subsequently drain into bigger structures - major calyces. ● Renal pelvis - funnel shaped structure formed by major calyces and continuous with

ureters.

Arterial supply to the kidney: ● Blood enters kidneys via the renal arteries which emerge directly from the abdominal aorta. Just inferior to the superior mesenteric artery. ● Left is slightly higher than the right. ● Right renal artery is longer (as aorta is to the left) and runs behind IVC. ● Renal arteries divide in the hilum/renal sinus into posterior, anterior and accessory segmental arteries to supply renal parenchyma. ● Segmental arteries branch into interlobar arteries. ● Interlobar arteries branch into arcuate arteries. ● Arcuate arteries branch into interlobular arteries. ● As interlobular arteries enter cortex they give off small branches - afferent arterioles. ● Afferent arteriole enters renal corpuscle and form ball of capillaries - glomerulus. ● Some plasma is filtered out of capillaries into capsular space. ● Remaining blood exits corpuscle and glomerulus in efferent arteriole. ● Efferent arterioles branch into one of two capillary networks: ○ Peritubular capillaries - surround the convoluted tubules and reside primarily in the cortex. ○ Vasa recta - associated mainly with nephron loop (of Henle) and primarily reside in the medulla.

Venous return from kidneys: ● Peritubular capillaries and vasa recta drain into a network of veins. ● Smallest veins are interlobular. ● These merge to form arcuate veins. ● Arcuate veins merge to form interlobar veins. ● Interlobar veins merge in the renal sinus to form the renal vein in each kidney. Nephrons: ● Functional unit of the kidney. ● Form urine through 3 processes: ○ Filtration ○ Absorption ○ Secretion Polycystic kidney disease: ● Genetic or acquired. ● Characterised by growth of fluid filled cysts in kidneys. ● PKD cysts can slowly replace much of the mass of the kidneys, reducing kidney function and leading to renal failure.

Horseshoe kidney: ● Most common type of renal fusion anomaly. ● Consists of two distinct functioning kidneys on each side of midline connected at lower poles by isthmus of functioning renal parenchyma OR fibrous tissue crossing midline of body. ● Twice as common in males. Suprarenal glands: ● Associated with superior pole of each kidney. ● With the kidneys are surrounded by perinephric fat and enclosed by renal fascia. ● Thin fibrous septum separates gland from kidney. ● Glands consist of a cortex and a medulla. ● Right suprarenal gland is pyramidal in shape, left is bigger and semilunar. ● Arterial supply relies on: ○ Superior suprarenal artery - originates from inferior phrenic artery. ○ Middle suprarenal artery - directly from abdominal aorta. ○ Inferior suprarenal artery - from renal artery. ● Venous return: ○ Right suprarenal vein drains directly into IVC, while left drains via left renal vein. Ureters: Narrow muscular tubes 25 cm in length. Transport urine from kidneys to bladder. Upper half of tube lies in abdominal cavity, lower half in pelvic cavity. Course in abdomen is the same in male and female - differs in pelvis. Ureteric constrictions: ● At ureteropelvic junction (junction with RENAL pelvis). ● At pelvic brim when crossing common iliac arteries - at sacroiliac joint. ● At entrance to bladder. Sites for occlusion - eg. lodging of a gallstone. Abdominal course: ● Right side: ○ Descends - crosses psoas and genitofemoral nerve. ○ Anteriorly it is crossed by: ■ Descending duodenum. ■ Root of duodenum. ■ Root of mesentery. ○ It is then adherent (PAW) and covered by peritoneum for remainder of course. ● Left side: ○ Descends on psoas and crosses genitofemoral nerve.

○ Crossed by: ■ Left colic and gonadal vessels. ■ Root of sigmoid mesocolon. Pelvic portion: ● Male: ○ Crosses common iliac vessels (anterior to sacroiliac joint) and descends on pelvic wall to ischial spine before turning forwards and medially just superiorly to levator ani. ○ Ductus deferens (sperm duct) crosses superiorly from lateral to medial near ischial spine. ● Female: ○ Similar as far as ischial spine, then turns forwards and medially under root of broad ligament. ○ Then crossed superiorly by uterine artery to lie in close relation with lateral fornix of vagina before entering bladder.

Blood supply to ureters: ● Arterial supply: ○ Upper part - branches from renal arteries. ○ Middle part - branches from abdominal aorta, gonadal arteries and common iliac arteries. ○ Lower part/pelvic cavity - branches from internal iliac arteries. ● Venous return and lymphatics: ○ Follow similar pattern to arterial supply. Urinary bladder: ● Hollow distensible muscular organ held in pelvic cavity by folds of peritoneum. ● Capacity of 700-800 mL. ● In men - anterior to rectum - forms rectovesical pouch. ● In women - anterior to vagina and inferior to uterus - forms rectouterine and vesicouterine pouches. ● Has pyramid shape. ○ Apex - posterior to pubic symphysis ○ Base - posteriorly ○ Superior aspect ○ Two inferolateral aspects. ● Trigone: ○ Small triangular area in floor of urinary bladder with mucosa firmly attached to muscularis - gives smooth appearance. ○ Two posterior corners contain ureteral openings. ○ Anterior corner contains urethral orifice.

Two ureters enter at the posterolateral angles of the base. Urethra leaves inferiorly at the neck surrounded by vesical sphincter. Here smooth muscle is found in both sexes: In males - circular. In females - longitudinal.

Fascia covers the bladder and thickens around its neck - forms ligaments. In the male - puboprostatic ligament from pubis to prostate. It is also held in place by continuity with the prostate. In the female - pubovesical ligament from pubis to bladder. Hence, bladder is more mobile in the female.

The interior of the bladder is rugose - except for the trigone area bounded by the three apertures of the bladder.

Micturition - discharge of urine. ● Consequence of voluntary (somatic motor) and involuntary (PS) muscle contractions and sphincter relaxations. ● Micturition centre (S2 and S3) is stimulated when bladder is full and pressure reflexes propagate to bladder. ● Detrusor muscle (dome of bladder) contracts and internal urethral sphincter relaxes via PS innervation. ● Somatic motor neurons of external urethral sphincter muscle are inhibited - allows urine to drain. Vasculature of urinary bladder: ● Arterial ○ Superior vesical artery - from umbilical artery. ○ Medial vesical artery - from umbilical OR superior vesical artery. ○ Inferior vesical artery - from internal iliac artery. ● Venous return ○ Veins from urinary bladder go to internal iliac vein. Innervation: ● Hypogastric sympathetic plexuses. ● Parasympathetic from 2nd and 3rd sacral nerves (pelvic splanchnic nerve). Splanchnic nerves are paired visceral nerves - carry fibres of autonomic nervous system (visceral efferents) and somatic nervous system (visceral afferents). Female urethra - terminal tubular structure. Lies posterior to pubic symphysis External urethral orifice opens between the clitoris and the vaginal opening. Male urethra - longer ~ 20 cm - and shared between genital and urinary systems. Divisions according to structures it travels through: ● Preprostatic urethra. ● Prostatic urethra. ○ Contains openings of ejaculatory ducts of prostate that release seminal fluid into urethra. ● Membranous urethra. ● Spongy urethra (longest portion) divisible into: ○ Bulbous portion. ○ Pendulous (penile) portion....