Urinary System

I. Functions of the Urinary System A. Maintain Water Balance B. Maintain Salt Balance C. Maintain pH [H+] D. Excretion of metabolic (biochemical) waste products = urea (breakdown product of proteins) and uric acid

Urea – major waste product in the body Uric acid – gouty arthritis or gout - formed from the breakdown of nucleic acids feces = food residues

Regions of the Urinary System A. Kidneys B. Ureters C. Urinary Bladder D. Urethral Canal (urethra)

Aorta – main artery of the body

Renal Artery

Purified blood leaves the kidney through the renal vein

Renal vein = lower in waste products, lower in oxygen Renal artery = higher oxygen Most organs in the body are pink because of the number of blood vessels and present in the vessels are red blood cells other organs that are not pink and most other cells/tissues are transparent or has no color

The Kidneys A. reddish-brown organs located retroperitoneally (the reddish color is due to the vascularity of the kidneys) B. the kidneys extend from about T-12 to L-3, with the right kidney located slightly lower than the left kidney

C. the kidneys are surrounded by renal capsule and perirenal fat – the fat is for protecting the kidney D. renal cortex “Note: interlobar arteries and veins extend through the renal columns of the cortex dividing the kidneys into lobes

E. Renal Medulla (Medullary Pyramids) Note: the urine collecting ducts pass downward through the renal medulla (pyramids) and open into the calyces of the ureter

Urinary System Kidneys – produce urine Ureters –transport urine to bladder Urinary bladder - stores urine Urethra transports urine to exterior Figure 26.1

Location and External Anatomy of Kidneys Located retroperitoneally Lateral to T12–L3 vertebrae Average kidney 12 cm tall, 6 cm wide, 3 cm thick Hilus On concave (curving in or hollowed) surface Vessels and nerves enter and exit Renal capsule surrounds the kidney

Urinary System in Gross Dissection Figure 26.3

Internal Gross Anatomy of the Kidneys Frontal section through the kidney Renal cortex Renal pyramids Renal pelvis Major calicies Minor calicies Gross vasculature Renal arteries Branch into segmental arteries

Anatomy of the kidneys Superficial outer cortex and inner medulla The medulla consists of 6-18 renal pyramids The cortex is composed of roughly 1.25 million nephrons Major and minor calyces along with the pelvis drain urine to the ureters

Nephron – The Functional Unit of Kidney Nephron consists of: Renal corpuscle Renal tubule: Proximal convoluted tubule (PCT) Loop of Henle Distal convoluted tubule (DCT) Nephron empties tubular fluid into a system of collecting ducts and papillary ducts

Renal Corpuscle Consists of: Glomerulus – tuft of fenestrated (perforations or apertures) capillaries Glomerular (Bowman’s) capsule Parietal layer – simple squamous epithelium Visceral layer – consists of podocytes (cells in the Bowman’s capsule) Blood travels from efferent arteriole to peritubular capillaries Blood leaves the nephron via the efferent arteriole Renal Corpuscle

Urine Collecting Duct (Papillary Duct)

Blood supply to the kidney Blood flow to the kidney involves a portal system Renal Artery Interlobar Artery Arcuate Artery Interlobar Artery Afferent Glomerular Arteriole Glomerular Capillaries or Capillary Bed (Glomerulus) Efferent Glomerular Arteriole (Portal Vessel) Peritubular Capillaries (Capillary Bed) & Vasa Recta Interlobar Vein Arcuate Vein

Most locations in the body are: Arteries Capillary Bed Vein But there are 3 places in our body wherein we have what we call portal systems What are portal systems? Portal system – 2 capillary beds in between Artery Capillary Bed Portal Vessel Capillary Bed Vein

Where can you find portal systems? 1. Hepatic Portal System 2. Kidney 3. Hypothalamic-Pituitary System Example in the liver: Arteries Capillaries Hepatic Portal Vein Liver Or Digestive Tract Arteries Capillaries Hepatic Portal Vein Capillaries Vein

Glomerular Capsule or Bowman’s Capsule – named after Dr. Bowman

Microanatomy of the Kidney A. The Nephrons (Renal Tubules) – cuboidal epithelial cells with microvilli 1. Glomerular (Bowman’s) Capsule a. encloses the glomerular capillaries 1. glomerular filtration of blood – some of the fluid in the bloodstream filters out into the glomerular capsule

2. Proximal Convoluted Tubule – location for tubular reabsorption - the “good stuff” (sugars & amino acids) is reabsorbed back into the bloodstream (going from the proximal convoluted tubule into the peritubular capillaries)

Loop of Henle (“Nephron Loop”) - located in the renal medulla - consists of a descending portion and an ascending portion (limb) Distal Convoluted Tubule – location for tubular secretion – certain specific chemicals are transported out of the peritubular capillaries into the distal convoluted tubule like excess H+, excess NaCl, pencillin antibiotics

The Urine Collecting Ducts (Papillary Ducts) – the nephrons empty into the urine collecting ducts, which conduct the urine down to the renal calyces of the ureter The Ureters – are a 10-inch long muscular tube that conduct urine from the kidneys to the urinary bladder by peristalsis

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