1. Anatomy & Physiology of the Excretory System

7. Why Are We Not Advised To Drink Seawater?

9. Water Balance Need appx. 3L/day
Without water, no hydrolysis, temperature regulation, transport of materials

11. HYPONATREMIA
3 Gal/1hr = death due to loss of electrolytes (salts), causing nervous conductivity and muscle contraction to cease

12. HYPONATREMIA
3 Gal/1hr = death due to loss of electrolytes (salts), causing nervous conductivity and muscle contraction to cease

13. Is the excretory system a misnomer?

14. Physiological Functions of Excretory System
The main function of the urinary system is to maintain homeostasis within the body by:
Eliminating nitrogenous wastes, toxins, and drugs from the body
Regulate the blood’s volume and chemical makeup so there is a proper balance between water & salts, and between acids and bases
Produce the enzyme renin (regulates blood pressure) and the hormone erythropoietin (stimulates RBC production in bone marrow)
Converts vitamin D to its active form

16. External Anatomical Features of Kidney
Two bean shaped organs in the dorsal wall of the body
The right kidney is slightly lower than the left, due to crowding from the liver
12th rib corresponds to middle of kidney

17. Renal Capsule & Perirenal Adipose
Kidneys are retroperitoneal (i.e. not protected by peritoneum like other abdominal organs)
Renal Capsule = Fibrous connective tissue that protects the kidney
Perirenal Adipose = protective layer of fat around kidney

18. Hydronephrosis
Ptosis = Rapid decline in extra-renal adipose may cause the kidneys may descend.
Descended kidney may lead to ureters become distended, backing up drainage to the urinary bladder.
This exerts pressure on the kidney tissues, a condition called hydronephrosis, which can severely damage the kidney

19. Internal Anatomy of Kidney

20. Renal Divisions Renal Capsule Renal Cortex Renal Medulla Renal Calyces
Renal Pelvis

21. Renal Medulla & Renal Cortex
Regions of filtration and reabsorption
Medulla – comprised of Malpighian Pyramids (site of reabsorption)
Cortex – contains Malpighian Corpuscle (site of filtration)

22. The Nephron Nephrons are the functional units of the kidneys
Located in renal cortex with extensions into the renal medulla
Comprised of Malpighian Corpuscles and Distal Convoluted Tubules

23. Malpighian Corpuscle
Glomerulus = bundle of capillaries containing waste-rich blood
Bowman’s Capsule = epithelial space surrounding glomerulus that receives wastes via filtration

24. Distal Convoluted Tubule
Long extension into the renal medulla for the process of reabsorption
Highly vascularized with capillaries

25. Renal Circulation
Blood from the aorta enters the Renal Hilum via the renal artery
Filtered of blood occurs in the glomerulus (bundles of capillaries) that are part of the nephrons in the renal medulla
Filtered blood exits via renal vein, to return to the heart via the inferior vena cava.

26. Urine Formation Urine formation is a two step process: (1) Filtration:
Nonselective, passive process that occurs in the glomerulus
Filtrate is essentially blood plasma, minus blood proteins (i.e. albumin)
Waste, excess ions, water, glucose, amino acids, and other key ions are part of this filtrate
Not producing enough filtrate for healthy volumes of urine, or blood cells/proteins in the urine can indicate problems with the glomerular filters

27. Urine Formation, Reabsorption
Takes place in the renal tubules; reclaiming important substances from the filtrate to put back into the blood stream
Some reabsorption is passive (requires no ATP)
EX: Water, NaCl
Most reabsorption is active (requires ATP)
EX: Glucose, amino acids
Nitrogenous waste products are poorly reabsorbed, so found in high concentrations in filtrate (urine)
EX: urea (from liver), uric acid (from metabolism of nucleic acids), and creatinine (creatine metabolism of muscle tissue)

28. Renal Calyces & Pelvis
Renal Calyces – collect filtrate from the renal papillae at the end of the Malpighian Pyramids
Renal Pelvis – collect filtrate from the renal calyces and direct it towards the ureter (exiting the renal hilus)

29. Ureters
Slender tubes that drain the urine from renal pelvis to urinary bladder
Though gravity does most of the work, the ureters are composed of visceral muscle that actively transport urine to the bladder via peristaltic waves
Urine backflow is prevented by valve-like folds of bladder mucosa that flap over the ureter openings

30. Renal Calculi

31. Renal Calculi
When urine becomes extremely concentrated, solutes such as uric acid salts form crystals that precipitate in the renal pelvis
These crystals are called renal calculi ( “kidney stones”)
They cause excruciating pain when the walls close in on the sharp calculi as they are passed through the ureter, or get wedged in a ureter
Frequent UTIs, urinary retention, and alkaline urine can lead to the formation of calculi
Kidney stones may pass naturally, be removed surgically, or, more recently, shattered with ultrasound waves (the fragments pass painlessly)

32. Urinary Bladder Located just posterior to the pubic symphysis
Smooth, collapsible, muscular sac that stores urine temporarily
Bounded by visceral detrusor muscle
Empty bladder 2-3 inches
Full bladder 5 inches

34. Urethra
Thin-walled tube that carries urine by peristalsis from the bladder to outside of the body
The internal urethral sphincter is composed of smooth muscle, and prevents urine from exiting the bladder (involuntary)
The external urethral sphincter is composed of skeletal muscle, and controls the rate at which urine leaves the urethra (voluntary)
In females, the external orifice is anterior to the vaginal opening; in males, the external orifice is at the tip of the penis

35. Male Urinary Tract

36. Female Urinary Tract

37. Micturition “Voiding” (emptying bladder)
When ~200mL of urine have collected in the bladder, this stretching activates receptors
The pelvic splanchnic nerves trigger the internal urethral sphincter to open, allowing urine into the upper part of the urethra
This is when you feel the urge to go to the bathroom; however, you control the external urethral sphincter (to a point)

38. Urinary Tract Infections (UTIs)
Bacterial infection of one part of the urinary tract
Cystitis is a bladder infection; typically accompanied by frequent urges, burning sensation during urination, cloudy urine
Urethritis is inflammation of the ureters; marked by frequent urges to urinate & painful urination
Women are 30 times more likely to develop a UTI than men, due to anatomical differences in the opening of the urethra
Cranberries contain a substance that helps prevent bacteria from adhering to the bladder walls