BIOH122 Human Biological Science 2 Session 16 Urinary System 1 The Kidneys Bioscience Department Endeavour College of Natural Health endeavour.edu.au
Session Plan o Functions of Urinary system o The Kidneys: Functions External and internal Anatomy Blood and Nerve Supply The Nephron Endeavour College of Natural Health endeavour.edu.au 2
Organs of The Urinary System o Two kidneys o Two ureters o One urinary bladder o One urethra Endeavour College of Natural Health endeavour.edu.au 3
Functions of Urinary system Endeavour College of Natural Health endeavour.edu.au 4
The Urinary System o Kidneys: Regulate blood volume and composition Regulate blood pressure, ph, and glucose levels Produce two hormones: Calcitriol and erythropoietin Excrete wastes in urine o Ureters: Transport urine from kidneys to urinary bladder. o Urinary Bladder: Stores urine and expels it into urethra. o Urethra: Discharges urine from body. Endeavour College of Natural Health endeavour.edu.au 5
The Kidneys Endeavour College of Natural Health endeavour.edu.au 6
Functions of the Kidneys o Regulation of blood ionic composition Na +, K +, Ca 2+, Cl -, and HPO4 2- o Regulation of blood ph, osmolarity and glucose o Regulation of blood volume conserving or eliminating water o Regulation of blood pressure secreting the enzyme renin adjusting renal resistance o Release of erythropoietin and calcitriol o Excretion of wastes and foreign substances Endeavour College of Natural Health endeavour.edu.au 7
External Anatomy of the Kidneys o Shape: bean-shaped organ o Size:10-12 cm long, 5-7 cm wide, 3 cm thick o Location: Retroperitoneal in the superior lumbar region (along with adrenal glands and ureters). Right kidney slightly lower. o Protected by: 11th and 12th ribs Marieb, and Hoehn, 2011 Endeavour College of Natural Health endeavour.edu.au 8
External Anatomy of the Kidneys o Three layers: surround each kidney: The renal capsule: Innermost The adipose capsule: Middle The renal fascia: Outer o The renal hilum/hilus: an indentation near the centre of the concave border For entry and exit of the ureter, blood vessels, lymphatic vessels, and nerves. Tortora, and Derrickson, 2012 Endeavour College of Natural Health endeavour.edu.au 9
Internal Anatomy of the Kidney o Two distinct regions: Renal medulla: a deep, darker reddish-brown inner region Renal pyramids renal papilla Renal cortex: a superficial, light red area o Renal lobe Renal columns o Parenchyma o Nephrons Endeavour College of Natural Health endeavour.edu.au 10
Internal Anatomy of the Kidneys Endeavour College of Natural Health endeavour.edu.au 11
Internal Anatomy of the Kidneys o Drainage of filtrate: Filtrate formed by the nephrons drains into: The papillary ducts Minor and major calyces Renal pelvis o From renal pelvis urine drains out through the ureter to the urinary bladder. o Renal sinus Endeavour College of Natural Health endeavour.edu.au 12
Blood Supply of the Kidneys o Abundantly supplied with blood vessels o Arterial supply: Renal arteries 20 25% of the resting cardiac output o Venous drainage: Renal veins carries venous blood to the inferior vena cava. Endeavour College of Natural Health endeavour.edu.au 13
Blood Supply of the Kidneys o 2 Capillary beds. (Glomerular, Peritubular) o 2 Arteriolar beds (Afferent, Efferent) o Capillary beds: Glomerular capillaries: filter blood Peritubular capillaries: carry away reabsorbed substances from filtrate Vasa recta: supplies nutrients to the medulla without disrupting its osmolarity formation Endeavour College of Natural Health endeavour.edu.au 14
Nerve Supply of the Kidney o Renal plexus: the sympathetic division of ANS. o Sympathetic vasomotor nerves regulate blood flow and renal resistance by altering arterioles o Cause vasodilation or vasoconstriction of renal arterioles Vasodilation / Vasoconstriction of afferent arteriole is an important response relating to regulating blood pressure Endeavour College of Natural Health endeavour.edu.au 15
The Nephron Endeavour College of Natural Health endeavour.edu.au 16
The Nephrons o The nephrons: The functional units of the kidneys About 1 million in each kidney o Each consists of: A renal corpuscle A renal tubule o Three basic functions of nephron: Glomerular filtration Tubular reabsorption Tubular secretion Tortora, and Derrickson, 2012 Endeavour College of Natural Health endeavour.edu.au 17
The Nephron o A renal corpuscle: Site of Plasma Filtration Glomerulus: Capillary network where filtration occurs Glomerular (Bowman s) capsule: Double-walled epithelial cup surrounding the glomerular capillaries that collects filtrate Endeavour College of Natural Health endeavour.edu.au 18
Renal Corpuscle The Nephron Glomerular capillary & Glomerular Capsule Proximal Convoluted Tubule (PCT) Loop of Henle Descending limb of the loop of Henle Ascending limb of the loop of Henle Distal Convoluted Tubule (DCT)
Passage of Filtrate / Urine in Kidney Distal Convoluted Tubule (DCT) Collecting Ducts Papillary Ducts Minor Calyx Major Calyx Renal Pelvis Urteter
The Nephrons o Two types of nephrons: based on structure and function. Cortical Nephron: 80-85% of nephrons Juxtamedullary Nephron: 15-20% of nephrons Have an important role in water reabsorption because of the length of their Loop of Henle into the medulla region Endeavour College of Natural Health endeavour.edu.au 21
o A cortical nephron: Cortical Nephrons Glomerulus: in the outer cortex Short Loop of Henle: penetrates only into the outer region of the medulla Endeavour College of Natural Health endeavour.edu.au 22
Juxtamedullary Nephrons A juxtamedullary nephron: Glomerulus: in the deeper cortex close to the medulla Long Loop of Henle: stretches through the medulla Endeavour College of Natural Health endeavour.edu.au 23
Blood Supply to the Nephron Tortora, and Derrickson, 2012 Endeavour College of Natural Health endeavour.edu.au 24
Histology of the Glomerular o Glomerular Capsule The visceral layer: podocytes The parietal layer Capsule Capsular space: the space between the two layers of the glomerular capsule. Where fluid is filtered to Endeavour College of Natural Health endeavour.edu.au 25
Histology of the Glomerular o Filtration (dialysis) membrane: Fenestrations formed by the visceral and parietal epithelium act as a filtration membrane. Filtration occurs via Blood Pressure Capsule Endeavour College of Natural Health endeavour.edu.au 26
Histology of the Renal Tubule and the Collecting Duct Designed for reabsorption Tortora, and Derrickson, 2012 Endeavour College of Natural Health endeavour.edu.au 27
Histology of the Renal Tubule and the Collecting Duct Principal cells: have receptors for ADH and aldosterone. Intercalated cells: play a role in the homeostasis of blood ph. Tortora, and Derrickson, 2012 Endeavour College of Natural Health endeavour.edu.au 28
Juxtaglomerular Apparatus Marieb, and Hoehn, 2011 Endeavour College of Natural Health endeavour.edu.au 29
Juxtaglomerular Apparatus o Juxtaglomerular Apparatus (JGA): A structure where afferent arteriole makes contact with ascending limb of loop of Henle o Constituted by: Macula densa: Crowded columnar cells in the final part of the ascending limb of the loop of Henle Juxtaglomerular cells: Modified smooth muscle fibers in the wall of the afferent arteriole o Function: Helps regulating blood pressure and the rate of blood filtration by the kidneys Endeavour College of Natural Health endeavour.edu.au 30
Number of Nephrons o Constant from birth: Hypertrophy of kidney occurs due to the growth of (size) individual nephrons. If nephrons are injured or become diseased, new ones do not form. o Kidney dysfunction: Signs usually do not become apparent until function declines to less than 25% of normal Remaining functional nephrons adapt to handle a larger-thannormal load. o Surgical removal of one kidney: stimulates hypertrophy (enlargement) of the remaining kidney, able to filter blood at 80% of the rate of two normal kidneys. Endeavour College of Natural Health endeavour.edu.au 31
Readings and Resources o Tortora, GJ & Derrickson, B 2014. Principles of Anatomy and Physiology, 14th edn, Wiley. o Harris, P, Nagy, S & Vardaxis, N 2010, Mosby s Dictionary of Medicine, Nursing and Health Professions, 2nd edn, Mosby Elsevier. o Guyton, AC & Hall, JE 2011, Textbook of Medical Physiology, 12th edn, Saunders Elsevier. o Marieb, EN & Hoehn, K 2011, Human Anatomy and Physiology, 9th edn, Benjamin Cummings Pearson. o Moore, KL, Dalley, AF & Agur, AMR 2010, Clinically Orientated Anatomy, 6th edn, Lippincott, Williams & Wilkins. Endeavour College of Natural Health endeavour.edu.au 32
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