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Functions of the Objectives Excretory System To begin unit on excretory system. The kidneys excrete nitrogenous wastes, such as urea, uric acid, creatinine and ammonium. I.D. elements of the gross anatomy. The kidneys maintain blood volume by - Kidney regulating water excreted. Monitor blood composition and blood pH by - Bladder regulating electrolyte excretion. - Sphincters Kidneys secrete the enzyme renin, which helps maintain blood pressure. Introduce the nephron and its general function. The kidneys secrete erythropoietin, which Learn some interesting facts about the stimulates RBC production. excretory system. Gluconeogenesis during prolonged fasting.
Hepatic veins (cut) Amazing Facts Esophagus (cut) Inferior vena cava About 1100-1200 liters of blood pass through the Renal artery Adrenal gland capillaries in our kidneys every day. Renal hilum Aorta Renal vein The kidneys filter nearly 200 liters of fluid from Kidney the bloodstream every day! Iliac crest Ureter Our kidneys extract about 180 L (45 gallons) of fluid/filtrate.
Rectum (cut) The kidneys refine the filtrate, and in a typical Uterus (part day we excrete only about 1.5 L of urine. of female Urinary reproductive bladder system) Urethra
Figure 25.1
Position said to be Retroperitoneal Renal hilum
Anterior Renal cortex Inferior vena cava Renal medulla Peritoneal cavity Aorta Peritoneum (organs removed) Supportive Major calyx tissue layers Renal vein • Renal fascia Renal pelvis anterior Renal posterior Minor calyx artery • Perirenal Ureter fat capsule Renal pyramid Body of • Fibrous in renal medulla vertebra L 2 capsule Renal column Body wall Fibrous capsule (a) Posterior (a) Photograph of right kidney, frontal section (b) Diagrammatic view
Figure 25.2a Figure 25.3
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Blood and Nerve Supply Function of the Nephron
1 Renal arteries deliver ~ /4 (1200 ml) of The functional unit of the kidney. cardiac output to the kidneys each Primary role is to filter the blood. minute. Produces concentrated urine. Most of the blood directed towards cortex, where urine production occurs. More than 1 million nephrons are Nerve supply is via sympathetic fibers packed into each kidney! from the renal plexus.
Location of the Nephron Primary parts of Nephron
o Found in the renal 1. Glomerulus: a tuft of capillaries cortex.
o Cortical nephrons 2. Renal tubule: begins as cup-shaped account for 85% in human kidney. glomerular (Bowman’s) capsule surrounding the glomerulus o Portions of the nephron extend into the renal medulla.
Urinary Bladder > Muscular sac for temporary storage of urine > Retroperitoneal, on pelvic floor posterior to pubic symphysis ◦ Males—prostate gland surrounds the neck inferiorly ◦ Females—anterior to the vagina and uterus
Figure 25.5
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Urinary Bladder Sphincters
Muscular sac for temporary storage of I. Internal urethral sphincter urine Involuntary (smooth muscle) at bladder-urethra junction Retroperitoneal, on pelvic floor posterior Contracts to open to pubic symphysis II. External urethral sphincter ◦ Males—prostate gland surrounds the neck Voluntary (skeletal) muscle surrounding the urethra inferiorly as it passes through the pelvic floor ◦ Females—anterior to the vagina and uterus
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