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: Kidney Group 2: Ureter Group 3: Urinary Bladder Group 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.
Cuboidal – not specialized for reabsorption

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
Substance
Amounted Filtered
Amount Excreted
Reabsorstion %
Water
180 L
1.8 L
99.0
Sodium
630g
3.2g
99.5
Glucose
180g
0.0
100
Urea
54g 30 44

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.

17. Glomerulus

18. Podocytes

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.