Urinary Tract Structure and Function - University of Bristol PDF

Urinary tract structure and function 1 Unit: AGEP Urinary Unit code: VETS10018 Dr Julie Dickson Senior Lecturer in Integrated Structure and Function [email protected] Learning outcomes Describe the division of the urinary tract into upper and lower. Describe the topographical anatomy...

Urinary tract structure and function 1 Unit: AGEP Urinary Unit code: VETS10018 Dr Julie Dickson Senior Lecturer in Integrated Structure and Function [email protected] Learning outcomes Describe the division of the urinary tract into upper and lower. Describe the topographical anatomy of the kidney for the main domestic species. Describe the internal gross anatomy of the kidney and explain how these features are used in classification of the kidney into multipyramidal (bovine), modified unipyramidal (dog, horse), and unipyramidal (cat, rodents). Briefly describe the blood supply of the kidney. Describe the nephron and the different sections of the nephron (e.g. renal corpuscle, PCT, loop of Henle, DCT, collecting duct). Describe and explain the gross anatomy and histological anatomy of the ureters and urinary bladder. Describe the innervation of the urinary bladder. Briefly describe the histology of the urethra. Overview of lecture We will go over: The topographical location of the kidneys. The structure of the kidneys and their blood supply. Discuss and explain the nephron, the functional unit of the kidney. Progress distally down the urinary tract and go over the ureters, urinary bladder, and urethra. Key definitions Renal = pertains to the kidneys. Renal sinus = a recess in the substance of the kidney, occupied by the renal pelvis, calices, vessels, nerves, and fat. Renal pelvis = the funnel shaped expansion of the proximal end of the ureter, it is usually within the renal sinus. Renal papilla = the blunted apex of a renal pyramid. Calix = a cuplike organ or cavity, for the kidney, one of the recesses of the kidney pelvis which enclose the tips of the pyramids. Renal lobe = comprising the tissue contributing to each pyramid.  Slide from Basic tissues of the body and body organisatio Urinary system The main organs of the urinary system: Pair of kidneys Ventral view of female - Filter the blood canine abdomen Pair of ureters - Drains urine from kidney Urethra Urinary bladder Learning outcomes Describe the division of the urinary tract into upper and lower. Describe the topographical anatomy of the kidney for the main domestic species. Describe the internal gross anatomy of the kidney and explain how these features are used in classification of the kidney into multipyramidal (bovine), modified unipyramidal (dog, horse), and unipyramidal (cat, rodents). Briefly describe the blood supply of the kidney. Describe the nephron and the different sections of the nephron (e.g. renal corpuscle, PCT, loop of Henle, DCT, collecting duct). Describe and explain the gross anatomy and histological anatomy of the ureters and urinary bladder. Describe the innervation of the urinary bladder. Briefly describe the histology of the urethra. Upper and lower urinary tract Upper Lower Kidneys Urinary Ureters bladder Urethra Pair of kidneys - Filter the blood Pair of ureters - Drains urine from kidney Urethra Urinary bladder Learning outcomes Describe the division of the urinary tract into upper and lower. Describe the topographical anatomy of the kidney for the main domestic species. Describe the internal gross anatomy of the kidney and explain how these features are used in classification of the kidney into multipyramidal (bovine), modified unipyramidal (dog, horse), and unipyramidal (cat, rodents). Briefly describe the blood supply of the kidney. Describe the nephron and the different sections of the nephron (e.g. renal corpuscle, PCT, loop of Henle, DCT, collecting duct). Describe and explain the gross anatomy and histological anatomy of the ureters and urinary bladder. Describe the innervation of the urinary bladder. Briefly describe the histology of the urethra. Overview of urinary tract The kidneys are paired. The kidneys form urine from blood. The ureters convey the urine from the kidneys to the urinary bladder. The urinary bladder stores the urine. The urethra is the passage from the bladder that the urine passes through to reach the exterior. In addition, the urethra in the male conveys the reproductive products. Kidneys – function To gain an appreciation of the anatomy of the kidneys it is helpful to think of this in combination with their main function. One of the main functions of the kidneys is to maintain the internal environment. Link to homeostasis lecture. The kidneys maintain the internal environment by filtering the plasma.  Reminder slide from ‘Blood and the circulation’ lectu Plasma composition Promotes blood clotting (coagulatio Plasma is made up of: Water Proteins primarily albumin, globulin, and fibrinogen Plasm Electrolytes such as Na+, Cl-, HCO3- a White blood Dissolved gases cells & Nutrients platelets such as glucose, lipids, amino acids, (Buffy layer) vitamins Red blood cells Waste products such as urea, creatinine, uric acid, lactic acid Hormones Kidneys – function Initially when filtering the plasma they extract a huge amount of fluid and then subject this ultrafiltrate to further processing, such as: Selectively reabsorbing useful substances. Concentrating waste products for elimination/removal in the urine. Altering water concentration to maintain the composition of plasma within the appropriate range.  What are the two endocrine functions of the kidneys? Rank Responses 1 1 What glands are situated near the kidneys? A. Adrenal B. Thyroid C. Parathyroid D. Pineal E. Pituitary Kidneys – gross anatomy The kidneys are a firm, reddish-brown gland. The external appearance of the kidneys varies among mammals: Kidney-shape – dogs, cats, small ruminants Flat-shape – pigs Heart-shape – horses Lobulated-shape – bovine The kidneys are usually found against the abdominal roof (i.e. dorsally) at the lumbar region. Generally, the right kidney sits further cranially than the left. Except for pigs  Kidneys – of different species ce, Sack and Wensing (2010) ‘Textbook of Veterinary Anatomy’, 4th Edition, St Louis, Mo: Saunders/Elsevie  Dyce, Sack and Wensing (2010) ‘Textbook of Veterinary Anatomy’, 4th Edition, St Kidneys – gross anatomy Louis, Mo: Saunders/Elsevier. The right kidney, sitting more cranially, within the renal impression (fossa) of the caudate liver lobe. The right kidney is a bit more firmly fixed because of liver fossa, while the left is more mobile and sags within the abdomen. In ruminants, the development of the large stomach occupying the left side of the abdomen pushes the left kidney into the right half of the Kidneys – gross anatomy The kidneys are each covered by a fibrous capsule that should peel off easily (except at the hilus). The ventral surface of the: R kidney – descending duodenum, pancreas, caecum, and ascending colon. L kidney – descending colon, jejunum (spleen is related to cranial pole). Kidneys – gross anatomy The kidneys are retroperitoneal and surrounded (or almost entirely covered) by fat. The kidneys have a nice smooth outer surface which is convex. The bovine kidneys have a smooth but lobulated texture. Kidneys – gross anatomy On the medial aspect of the kidneys there is an indentation. The indentation leads to a space, the renal sinus, which is occupied by the start of the ureter, the renal pelvis. Vessels, nerves, and fat are also located at the indentation. The indentation is referred to as the hilus. Hilus = a depression or pit on an organ, giving entrance and exit to vessels and nerv Learning outcomes Describe the division of the urinary tract into upper and lower. Describe the topographical anatomy of the kidney for the main domestic species. Describe the internal gross anatomy of the kidney and explain how these features are used in classification of the kidney into multipyramidal (bovine), modified unipyramidal (dog, horse), and unipyramidal (cat, rodents). Briefly describe the blood supply of the kidney. Describe the nephron and the different sections of the nephron (e.g. renal corpuscle, PCT, loop of Henle, DCT, collecting duct). Describe and explain the gross anatomy and histological anatomy of the ureters and urinary bladder. Describe the innervation of the urinary bladder. Briefly describe the histology of the urethra. Kidneys on cross-section The parenchyma of the kidneys are enclosed by a tough fibrous capsule (as discussed earlier). When a kidney is cut in cross-section you can clearly see the parenchyma is divided into: Outer cortex Inner medulla Parenchyma = the essential or functional elements of an org Kidney – medulla In many species, the inner medulla is arranged as several discrete masses each roughly a pyramid shape. The base of the pyramid is capped by the cortex. The apex of the pyramid points towards the renal sinus and forms a papilla. The papilla fits into a cuplike expansion (called a calix) of the renal pelvis. Renal papilla = the blunted apex of a renal pyramid. Calix = a cuplike organ of cavity, for the kidney, one of the recesses of the kidney pelvis which enclose the Kidney – medulla Each of these medullary pyramids with its associated outer cortex forms a renal lobe. Kidneys with this organization are called multipyramidal or multilobar. The external lobes of the bovine kidneys mark the boundaries between the internal pyramidal lobes. All mammalian kidneys pass through a multipyramidal phase in their embryological development.  Kidneys – pyramids Renal lobes are fused to varying degrees depending on species: Multipyramidal Unipyramidal - Renal lobes divided into separate units - Renal lobes fused Cortex is fused Cortex and medulla Unipyramidal Multipyrami but medulla is not fused. Forms a (complete dal 18-25 (i.e. common renal crest fusion) lobes multipyramidal which may be internally) ridged giving the appearance of Kidney – blood supply Each kidney is supplied by a renal artery, a direct branch from the abdominal aorta. The renal artery then divides into several interlobar arteries. These follow the divisions between the renal pyramids (still present or use to be present). The interlobar arteries give rise to arcuate arteries. These arteries curve over the base of the pyramids. The interlobar arteries give rise to interlobular arteries and are located in the cortex. These give rise to the afferent arteriole supplying the renal glomerulus. Learning outcomes Describe the division of the urinary tract into upper and lower. Describe the topographical anatomy of the kidney for the main domestic species. Describe the internal gross anatomy of the kidney and explain how these features are used in classification of the kidney into multipyramidal (bovine), modified unipyramidal (dog, horse), and unipyramidal (cat, rodents). Briefly describe the blood supply of the kidney. Describe the nephron and the different sections of the nephron (e.g. renal corpuscle, PCT, loop of Henle, DCT, collecting duct). Describe and explain the gross anatomy and histological anatomy of the ureters and urinary bladder. Describe the innervation of the urinary bladder. Briefly describe the histology of the urethra. Diagram of blood supply Interlobular artery Interlobar artery Arcuate artery Renal artery The veins which lead to the caudal vena cava are generally sate Learning outcomes Describe the division of the urinary tract into upper and lower. Describe the topographical anatomy of the kidney for the main domestic species. Describe the internal gross anatomy of the kidney and explain how these features are used in classification of the kidney into multipyramidal (bovine), modified unipyramidal (dog, horse), and unipyramidal (cat, rodents). Briefly describe the blood supply of the kidney. Describe the nephron and the different sections of the nephron (e.g. renal corpuscle, PCT, loop of Henle, DCT, collecting duct). Describe and explain the gross anatomy and histological anatomy of the ureters and urinary bladder. Describe the innervation of the urinary bladder. Briefly describe the histology of the urethra. The nephron The nephron is the functional unit within the kidney. Simplistically and in layman's terms, it is a really long epithelial tube divided into different sections with varying convolutions (twists and turns). The nephron Each interlobular artery gives rise to a cluster of capillaries called the glomerulus. The nephron begins as a blind ended cup-shape expansion, invaginating the glomerulus. The glomerulus and the cup-like expansion of the nephron are collectively called a renal corpuscle. The nephron The renal corpuscles are scattered across the cortex giving the cortex a fine granular appearance. The long epithelial nephron tubule is then sequentially divided into the following sections: Proximal convoluted tubule Descending and ascending limb of nephron Distal convoluted tubule Collecting tubules and ducts The nephron – Proximal convoluted tubule Proximal convoluted tubule Longest and most convoluted part of the nephron comprising much of the renal cortex. A rich capillary network surrounds the proximal convoluted tubule and returns absorbed molecules to the circulation. Lined by a simple cuboidal epithelium with a prominent brush border. The nephron – Descending and ascending limb of nephron/loop of Henle Loop of Henle Starts at cortex and extends into medulla. The thick descending/ascending limbs lined by cuboidal epithelium. The thin descending/ascending limbs lined by simple squamous epithelium. The nephron – distal convoluted tubule Shorter tubule. Lacks a brush border compared to proximal convoluted tubule. Has a larger lumen on transverse cross-section. The nephron – Collecting duct Each collecting tubule serves many nephrons. Opens into a large papillary duct close to the apex (i.e. tip of pyramid). Learning outcomes Describe the division of the urinary tract into upper and lower. Describe the topographical anatomy of the kidney for the main domestic species. Describe the internal gross anatomy of the kidney and explain how these features are used in classification of the kidney into multipyramidal (bovine), modified unipyramidal (dog, horse), and unipyramidal (cat, rodents). Briefly describe the blood supply of the kidney. Describe the nephron and the different sections of the nephron (e.g. renal corpuscle, PCT, loop of Henle, DCT, collecting duct). Describe and explain the gross anatomy and histological anatomy of the ureters and urinary bladder. Describe the innervation of the urinary bladder. Briefly describe the histology of the urethra. Ureters The proximal end of the ureter is either: Expanded to form the renal pelvis (most domestic species; carnivores, horse, sheep) The papillae drain into calyces which drain into two branches of ureter (bovine). The papillae drain into calyces which drain into a renal pelvis (Pig). Proximal ureter Ureter The inner mucosal lining forms longitudinal folds allowing for expansion. Consists of two muscular coats: Outer circular Inner longitudinal Peristaltic waves of contraction move the urine to the bladder. Penetrate the dorsal surface of the urinary bladder wall at an oblique angle. Urinary bladder The urinary bladder is very distensible and because of this doesn’t have a constant size, position or relationship to other organs. The urinary bladder consists of: Apex Body Neck The urinary bladder is supported by three ligaments: Median ligament x1 – runs from the apex to umbilicus (in the foetus supporst the urachus) Lateral ligaments x2 – run from bladder to pelvic wall (contain the round ligaments which are remnants of the umbilical arteries) Urinary bladder When empty the mucosa of the urinary bladder is corrugated and has a negligible lumen. When the urinary bladder extends with the filling of urine it becomes pear shaped with an obvious apex, body, and neck. As the urinary bladder distends with urine it extends into the abdomen, but the neck remains fixed in the pelvis due to its continuation with the urethra. Ureters and Bladder The ureters enter the bladder on the dorsal surface at an angle. The angle prevents urine flowing back up the ureter. Urinary bladder muscles The bladder muscle is made up of three sheets of muscles. The arrangements of three sheets is often described as detrusor (detrusor = a general term for a muscle that expresses a substance). The external sphincter is formed by the striated urethralis m. Learning outcomes Describe the division of the urinary tract into upper and lower. Describe the topographical anatomy of the kidney for the main domestic species. Describe the internal gross anatomy of the kidney and explain how these features are used in classification of the kidney into multipyramidal (bovine), modified unipyramidal (dog, horse), and unipyramidal (cat, rodents). Briefly describe the blood supply of the kidney. Describe the nephron and the different sections of the nephron (e.g. renal corpuscle, PCT, loop of Henle, DCT, collecting duct). Describe and explain the gross anatomy and histological anatomy of the ureters and urinary bladder. Describe the innervation of the urinary bladder. Briefly describe the histology of the urethra. Urinary bladder – innervation Autonomic fibres reach the urinary bladder via: Sympathetic from hypogastric nerves – urine storage e.g. continence Parasympathetic from pelvic nerves – urine evacuation e.g. micturition Sensory fibres are reached via the pudendal nerve. Blood supply to urinary bladder via vaginal (or prostatic) artery and supplemented by reduced umbilical arteries. Vaginal (or prostatic) a. branch of the internal iliac a. Learning outcomes Describe the division of the urinary tract into upper and lower. Describe the topographical anatomy of the kidney for the main domestic species. Describe the internal gross anatomy of the kidney and explain how these features are used in classification of the kidney into multipyramidal (bovine), modified unipyramidal (dog, horse), and unipyramidal (cat, rodents). Briefly describe the blood supply of the kidney. Describe the nephron and the different sections of the nephron (e.g. renal corpuscle, PCT, loop of Henle, DCT, collecting duct). Describe and explain the gross anatomy and histological anatomy of the ureters and urinary bladder. Describe the innervation of the urinary bladder. Briefly describe the histology of the urethra. Urethra Female Male Urethra lined Prostatic urethra lined by predominantly by urinary urinary epithelium. epithelium. Otherwise male urethra At the external urethral lined by orifice there is a change stratified/pseudostratified to stratified squamous columnar epithelium. epithelium. References Dyce, Sack and Wensing (2010) ‘Textbook of Veterinary Anatomy’, 4th Edition, St Louis, Mo: Saunders/Elsevier. Sjaastad et al (2016). Physiology of domestic animals. (3rd ed.). Oslo, Norway: Scandinavian Veterinary Press.