Excretory System

1. Excretory System Yummmmmm… Nephrons

2. Mind Maps • Get into groups of 3-4 – use iPads to create a mindmap • On iThoughtsHD create a mind map on thoughts, ideas, knowledge

3. Functions on the Urinary System • Excretion of Metabolic Wastes • Maintenance of water – salt balance • Maintenance of acid – base balance • Secretion of hormones

4. Excretion of Metabolic Wastes • Excrete nitrogenous wastes • Urea is the primary nitrogenous waste • By product of nucleic acid breakdown • Liver releases ammonia (extremely toxic to cells) • Forms with carbon dioxide to form urea • If too much uric acid is present in the blood, can precipitate causing crystal = gout • Others wastes include methane

5. Maintenance of Water-Salt Balance • Blood volume is closely associated with the salt balance of the body • The greater amount of salt in the blood, the greater the blood volume, the greater the blood pressure • Kidneys are responsible for filtering the blood of appropriate ions (Sodium, Potassium, Chloride etc…)

6. Maintenance of Acid-Base Balance • Kidneys monitor and maintain a pH of 7.4 • Excretes hydrogen ions • Reabsorbs bicarbonate ions

7. Secretion of Hormones • Assist in the endocrine function of the human body • Releases rennin which stimulates the release of aldosterone from the adrenal glands • Promotes the reabsorption of Na+ ions from the kidney

8. Organs of the Urinary System • Consists of the kidneys, ureters, urinary bladder and urethra • Numbered off into groups 1-4, learn the specific function of the specific organ • Group 1: KidneyGroup 2: UreterGroup 3: Urinary BladderGroup 4: Urethra • 1 person is nominated to write brief description onto the board

9. THE URINARY SYSTEM • Wastes filtered from blood by kidneys. • Wastes travel to bladder through ureters. • Kidney cross section: Cortex: outer layer. Medulla: inner layer. Renal pelvis: hollow, central chamber.

10. Gross Anatomy of the Kidney Renal Cortex: outer granulated layer that dips down Renal Medulla: Consists of cone shaped tissues Renal Pelvis: Is a central space or cavity that is continuous with the ureters

11. NEPHRONS • Multiple small tubes. • Functional unit of kidneys. • Afferent arterioles supply blood. • Branch into capillary bed or glomerulus. • Blood leaves glomerulus through efferent arterioles.

12. NEPHRONS CONTINUED • Glomerulus surrounded by Bowman’s capsule. • Urine carried through proximal tubule (lined with microvili) to the loop of Henle (lined with simple squamous epithelium) • Urine continues to distal tubule (cuboidal epithelial cells) and into collecting ducts. • Collecting ducts merge in renal pelvis and expel urine into ureters.

13. ANATOMY

14. Glomerular Filtration Rate • Occurs when the blood enters the afferent arteriole and the glomerulus • Due to glomerular blood pressure, water and other small molecules move from blood into the filtrated urine

15. Glomerular Filtration • Nephrons in kidney filter 180 liters of water per day ,including a small amount of molecules such as glucose and ions

16. FILTRATION • Individual nephrons have own blood supply. • Blood moves through afferent arteriole into glomerulus. • Glomerulus under high pressure. • Solutes diffuse across glomerulus walls into Bowman’s capsule. • Materials move from high pressure to low pressure.

19. THE FILTRATE • Not all blood components pass through capillary wall. • Small molecules and ions pass through easily. • E.g. Water, glucose, salts, amino acids. • Large molecules and structures remain in blood. • E.g. RBCs, platelets, proteins.

20. REABSORPTION • Urine formation water intensive. • Water and other important salts and molecules must be reabsorbed. • Active and passive transport used. • Na+ transported across nephron cell membrane. • Excess salts excreted in urine when threshold level reached.

21. REABSORPTION • Glucose and amino acids actively transported back into blood. • Some urea and uric acid is reabsorbed by this process.

22. SECRETION • Movement of wastes into nephron. • E.g. Nitrogenous wastes, surplus ions. • Active transport. • Mitochondria line distal tubule.

24. WATER BALANCE • Increased water intake → increased urine production. • Increased exercise, decreased water intake → reduced urine production and concentrated urine.

25. ANTIDIURETIC HORMONE (ADH) • Increases water reabsorption. • More concentrated urine results. • Produced by nerve cells of hypothalamus and stored in pituitary gland. • Pituitary gland releases ADH into blood. • Osmoreceptors in hypothalamus detect changes in body osmotic pressure. • Hypothalamus shrinks and sends nervous signals to pituitary gland. • ADH released into blood. • Thirst.

26. ADH ACTION ON NEPHRON • All parts of nephron not always permeable to water. • ADH makes upper section of distal tubule and collecting duct permeable to water. • High concentration of NaCl in interstitial fluid draws water back into interstitial space.

27. ANTIDIURETIC HORMONE (ADH) ABSENT PRESENT

28. REGULATION OF BLOOD PRESSURE • Kidneys regulate blood pressure by controlling blood volume. • Aldosterone produced in adrenal glands increases causing water reabsorption and increased blood volume.

29. RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM • Blood pressure receptors near glomerulus detect drop in blood pressure. • Renin released. • Converts angiotensinogen to angiotensin. • Blood vessels constrict. • Also stimulates release of more aldosterone.