Lecture 27: Anatomy of the Abdomen III Posterior - HUB105 UWC PDF

Lecture 27 Anatomy of the Abdomen III Posterior Abdominal Wall & Kidneys HUB105 UWC  Posterior Abdominal Region The posterior abdominal region is posterior to the abdominal part of the GIT, bounded by bones and muscles making up the posterior abdominal wall. S...

Lecture 27 Anatomy of the Abdomen III Posterior Abdominal Wall & Kidneys HUB105 UWC  Posterior Abdominal Region The posterior abdominal region is posterior to the abdominal part of the GIT, bounded by bones and muscles making up the posterior abdominal wall. Structures that pass through this area include the abdominal aorta, IVC, sympathetic trunks and lymphatics. The kidneys and suprarenal glands are also located in this region. 2  Psoas Major Thoracic diaphragm Origin: lateral surface of vertebral bodies, transverse processes and intervertebral discs of T12 to L5. Insertion: lesser trochanter of femur. Innervation: anterior rami of L1 to L3 spinal nerves. Function: flexion of thigh at hip joint. Psoas major Psoas Minor Psoas minor Absent in 40% of the Origin: lateral surface of vertebral population bodies of T12 and L1 and intervening intervertebral disc. Insertion: pectineal line and iliopubic eminence. Innervation: anterior rami of L1 spinal nerve. Function: weak flexion of lumbar region. 3  Quadratus lumborum Thoracic diaphragm Origin: transverse process of L5 vertebra, iliolumbar ligament and iliac crest. Insertion: transverse processes of L1 to L4 vertebrae, lower border of 12th rib. Innervation: anterior rami of T12 to L4 spinal nerves. Quadratus lumborum Function: depresses and stabilizes 12th rib; lateral bending of trunk. Iliacus Iliacus Origin: iliac fossa, sacrum, iliolumbar and anterior sacroiliac ligaments. Insertion: lesser trochanter of femur. Innervation: femoral nerve. Function: flexion of thigh at hip joint. 4 Lumbar Plexus Psoas major muscle Iliacus muscle 5  Kidneys Description – Paired, bean-shaped and retroperitoneal, lie Partially protected by lumbar vertebrae immediately lateral to vertebral column and lower rib cage. – Extend from T12 to L3 vertebrae; right kidney a little lower because of relationship with liver – 2 poles: superior and inferior – 2 surfaces: anterior and 11 rib th T12 posterior Left kidney Right kidney L3 – 2 borders: medial and lateral Ureter Superior poles capped by the suprarenal gland Medial border contains Urinary a hilum bladder 6 Posterior view  IVC Suprarenal gland Right Kidney Superior pole Renal capsule Right Left kidney kidney Aorta Ureter Renal a. Lateral border Renal v. Anterior view Hilum A typical adult kidney is reddish-brown and about 10 cm long, 5 cm wide, and 3 cm thick. It weighs Ureter about 150 g. The hilum is the point of entry for the renal artery and renal nerves, and a point of exit Inferior pole for the renal vein and ureter. 7  Kidneys Renal Fat & Fascia – The kidneys are enclosed in a unique arrangement of fascia and fat; maintains kidneys’ position – Fibrous capsule: layer of collagen fibres; covers outer surface of entire organ – Perinephric fat: accumulation of extraperitoneal fat outside the fibrous capsule; also called perirenal fat – Renal fascia: dense, fibrous outer layer enclosing the perinephric fat; anchors the kidney to surrounding structures – Paranephric fat: final layer; accumulates posterior and posterolateral to each kidney; also called pararenal fat 8  Renal Fat & Fascia Renal capsule Paranephric fat Renal fascia Renal capsule Posterior Right kidney colon Liver Pancreas Anterior The hilum leads into the renal sinus, a Renal sinus Perinephric fat cavity filled with fat and connective tissue. Structures that enter and leave the kidney pass through the renal sinus. 9  Kidneys Kidney Internal Anatomy – The substance of the kidney is divided into two distinct regions, visible to the naked eye: cortex and medulla – Renal cortex: superficial reddish-brown, granular region; in contact with renal capsule – Renal medulla: inner, lighter region; The colour difference reflects blood flow through the two regions; 90-95% of blood passing through the kidney is in the cortex, 5-10% is in the medulla – The medulla contains 6 to 18 conical structures called renal pyramids – base abuts cortex, tip (called papilla) projects into renal sinus – Renal pyramids are separated by bands of cortical tissue called renal columns that extend into medulla 10  Renal column Renal column Cortex Renal pyramid Renal Medulla pyramid Renal sinus Base Renal Renal pelvis Papilla sinus Ureter Renal lobe A renal lobe consists of a renal pyramid, the overlying area of renal cortex, and adjacent tissues of renal columns. 11  Kidneys Kidney Internal Anatomy – Each renal lobe contains many small ducts that produces urine and drain into cup-shaped channels called minor calyces – Minor calyces: each minor calyx usually surrounds a single papilla; the minor calyces join with their neighbours to form larger chambers called major calyces – Major calyces: the major calyces converge to form a large funnel-shaped renal pelvis – Urine flow: papilla >> minor calyx >> major calyx >> renal pelvis >> ureter 12  Renal column Renal pyramid Minor calyx Papilla Major calyx Renal pelvis Cortex Ureter Medulla 13  Kidneys Renal Blood Supply – Kidneys receive 20-25% of cardiac output; 1200mL of blood flows through each kidney per minute Renal artery – branch of abdominal aorta; divides into segmental arteries Segmental arteries – branches of renal artery as it enters renal pelvis; divide into series of interlobar arteries Interlobar arteries – radiate outwards through renal columns, between renal pyramids; give off arcuate arteries Arcuate arteries – arch along the boundary between the medulla and cortex of the kidney; each arcuate artery gives rise to several cortical radiate arteries Cortical radiate arteries – supply cortical portions of adjacent renal lobes; each one gives off numerous efferent arterioles and these deliver blood to individual nephrons 15  Renal Blood Supply Right renal artery Arcuate Radiate arteries arteries Renal artery Segmental arteries Cortex Arcuate artery Medulla Interlobar Interlobar artery arteries 16 Renal Blood Supply Cortical radiate vein Glomerulus Afferent arterioles Cortical radiate artery Arcuate artery Cortical Arcuate vein nephron Renal Juxtamedullary Cortical pyramid nephron radiate veins Cortical radiate Interlobar vein arteries Interlobar artery Interlobar Cortex arteries Segmental artery Minor calyx Medulla Circulation in a single renal lobe Renal artery Renal Renal vein Renal artery vein Segmental arteries Interlobar veins Interlobar arteries Interlobar Arcuate veins veins Arcuate veins Arcuate arteries Arcuate arteries Cortical radiate veins Cortical radiate arteries A sectional view, showing major arteries and veins Venules Afferent arterioles NEPHRONS Peritubular Glomerulus capillaries Efferent arteriole A flowchart of renal circulation 17  Kidneys Renal Histology – The kidney consists of many tortuous, closely-packed tubules surrounded by connective tissue – Each tubule consists of 2 embryologically distinct parts: nephron – produces urine; collecting duct – concentrates urine and carries it to the ureter – Nephron: consists of a renal corpuscle – filters plasma, and a renal tubule – selective resorption of filtrate to form urine The nephron is the kidney’s histological and functional unit – Collecting ducts: carry urine from several renal tubules to a terminal papillary duct; opens into minor calyx at the apex of the renal papilla 18  Renal Corpuscle Renal corpuscle: consists of the glomerulus (network of capillaries) and Bowman’s capsule. Renal tubule: long tubular passageway, begins renal corpuscle. Consists of proximal convoluted tubule, loop of Henle, and distal convoluted tubule. Collecting Ducts Collecting ducts receive fluid from many nephrons. Each duct carries fluid to a papillary duct that drains into a minor calyx. 19  Kidney Histology Nephrons – Renal corpuscle: each comprises of a central tuft of capillaries, the glomerulus; surrounded by a glomerular capsule called Bowman’s capsule – Glomerulus: network of capillaries supplied by afferent arteriole and drained by efferent arteriole Mesangial cells – located between capillaries – Bowman’s capsule: cup-like sac at beginning of renal tubule; encloses the glomerulus and collects fluid Capsular space filtered from blood = glomerular filtrate Parietal layer – outer layer; lined with simple squamous epithelium; also called capsular layer Parietal Visceral layer – inner; composed of branched cells called podocytes; forms a filtration membrane Capsular space – between parietal and visceral layers; also called urinary or Bowman’s space Visceral efferent afferent 20  Glomerular capsule Nucleus Capsular Glomerular Capsular Visceral Podocyte space capillary epithelium epithelium (podocyte) Pores Proximal Mesangial Efferent convoluted cell arteriole tubule Capillary Distal endothelial convoluted cell Filtration tubule Dense slits layer RBC Pedicels Capsular space Afferent Capsular arteriole epithelium Important structural features of a renal This cross section through a segment of corpuscle the glomerulus shows the components of the filtration membrane of the nephron. Filtration occurs in the renal corpuscle. Blood pressure forces water and dissolved solutes out of the glomerular capillaries into the capsular space. This produces a protein-free solution (filtrate) similar to blood plasma. 21  Kidney Histology Nephrons – Renal tubule: tubes into which fluid passes; each renal tubule consists of: Proximal convoluted tubule Nephron loop (loop of Henle) Distal convoluted tubule – Filtrate gradually changes composition along renal tubule – Each nephron empties into collecting ducts – Functions: (1) reabsorb useful organic nutrients that enter filtrate (2) reabsorb more than 90% of water in filtrate (3) secrete waste products that failed to enter filtrate 22  NEPHRON Proximal convoluted tubule Distal convoluted tubule Reabsorption of water, Secretion of ions, acids, ions, and all drugs, toxins organic nutrients Variable reabsorption of The proximal and distal convoluted water, sodium ions, and calcium ions (under hormonal control) tubules are located in the cortex. They are separated by a U-shaped Renal tubule nephron loop, also called the loop Capsular space Glomerulus of Henle. Efferent arteriole Afferent arteriole Glomerular capsule Descending Ascending limb of limb of loop ends Renal corpuscle loop begins Production of filtrate Thick Thin descending ascending limb limb The limbs of the loop of Henle are narrower and thin-walled and extends partially into the medulla Descending Ascending forming the descending and ascending thin segments. limb limb KEY Filtrate Water reabsorption Nephron loop Variable water reabsorption Further reabsorption of water Solute reabsorption or secretion (descending limb) and both sodium and chloride Variable solute reabsorption ions (ascending limb) or secretion 23  Juxtaglomerular Complex (JGC) Consists of macula densa – tall epithelial cells of DCT near renal corpuscle, and unusual smooth muscle fibres of afferent arteriole closely associated with macula densa called juxtaglomerular cells. Also called the juxtaglomerular apparatus. Proximal Efferent convoluted arteriole tubule Distal convoluted tubule Macula densa Juxtaglomerular cells Juxtaglomerular complex Afferent arteriole The JGC is an endocrine structure, it secretes renin and erythropoietin. 24  PCT Renal DCT corpuscle Loop of Henle 25  Kidney Histology Cortical nephrons – 85% of all nephrons – Located mostly within superficial cortex of kidney – Nephron loop (loop of Henle) is relatively short – Efferent arteriole delivers blood to a network of peritubular capillaries Juxtamedullary nephrons – 15% of nephrons – Nephron loops extend deep into medulla – Peritubular capillaries connect to vasa recta 26  Efferent Peritubular Cortical arteriole capillaries nephron Afferent arteriole Distal convoluted Renal tubule corpuscle Juxtamedullary Cortex nephron Collecting duct Peritubular capillaries Nephron loop The circulation to a cortical nephron Peritubular capillaries Proximal convoluted tubule (PCT) Medulla Glomerulus Distal convoluted Collecting duct tubule (DCT) Vasa recta Papillary duct Collecting duct Renal papilla Vasa recta Nephron Minor calyx loop The general appearance and location of The circulation to a nephrons in the kidneys juxtamedullary nephron 27  Kidney Histology Collecting Tubules – Renal tubules empty into the collecting system: a system of tubes that carries tubular fluid away from the nephron – Collecting ducts receive from many nephrons – Each collecting duct: Begins in the cortex Descends into the medulla Carries fluid to the wider papillary duct that drains into the minor calyx – Typically lined with simple columnar epithelium – Functions: Adjust fluid composition Determine final osmotic concentration and volume of urine 28  COLLECTING SYSTEM KEY Filtrate Water reabsorption Variable water reabsorption Solute reabsorption or secretion Variable solute reabsorption or secretion Collecting duct Collecting duct Variable reabsorption of water and reabsorption or secretion of sodium, potassium, hydrogen Collecting ducts originate in the cortex and empty and bicarbonate ions into wider papillary ducts which open on to a papilla into a minor calyx. Papillary duct Delivery of urine to minor calyx Minor calyx 29  Glomerular capsule: parietal layer Renal cortex Basement Renal medulla membrane Renal corpuscle Podocyte Renal pelvis Glomerular capsule Fenestrated Glomerulus endothelium Distal of the glomerulus Ureter convoluted Glomerular capsule: visceral layer tubule Kidney Microvilli Mitochondria Proximal convoluted tubule Highly infolded plasma membrane Cortex Proximal convoluted tubule cells Medulla Thick segment Distal convoluted tubule cells Thin segment Loop of Henle Descending limb Ascending limb Collecting Loop of Henle (thin-segment) cells duct Principal cell Intercalated cell Collecting duct cells 30  Revision Questions 1. Describe the location, size and shape of the kidneys. 2. Describe the renal capsule and the layers that surround the kidney. 3. What is the functional unit of the kidney? Name its parts. 4. List the components of the renal corpuscle. 5. Describe the structure of Bowman’s capsule, the glomerulus, and the filtration membrane. 6. Describe the juxtaglomerular complex. What is its function? 7. Distinguish between cortical and juxtaglomerular nephrons. 8. Describe the histological structure and location of the: a. Proximal convoluted tubule b. Loop of Henle c. Distal convoluted tubule d. Collecting ducts e. Papillary ducts 9. Describe the blood supply of the kidney. 32