Lecture Outline - Chapter 9

 
9.1 Urinary System (p. 184)
	1.	Urinary Organs (p. 184, Fig. 9.2)
		a.	The kidneys are bean-shaped organs that produce urine. They are protected by fibrous connective as well as adipose tissue.
		b.	The ureters are muscular tubes that lead away from a kidney and convey urine to the urinary bladder.
		c.	The urinary bladder is a distensible, muscular organ that stores urine until it can be expelled. 
		d.	The urethra, which extends from the urinary bladder to an external opening, is much longer in males than in females.
	2.	Urination and the Nervous System (p. 184, Fig. 9.3)
		a.	When the urinary bladder fills with urine to 250 of its total 600 milliliters, stretch receptors send impulses to the spinal cord. 
		b.	Urination results when returning nerve impulses cause the sphincters to relax and the bladder to contract.
	3.	Functions of the Urinary System (p. 185)
		a.	The kidneys maintain homeostasis by regulating the water and salt balance as well as the pH of the blood, and they excrete nitrogenous wastes generated by amino acid, uric acid, and creatinine metabolism.
		b.	The kidneys regulate blood pressure by adjusting the blood's water and salt content. 
		c.	The kidneys secrete erythropoietin, which stimulates red blood cell production.
		d.	The kidneys help activate the vitamin D precursor that eventually helps with calcium reabsorption during digestion. 
			HEALTH FOCUS: Urinary Tract Infections Require Attention (p. 186, Fig.9A)
			i.	Urinary tract infections are much more common in women than in men due to differences in anatomy.
			ii.	Urinary tract infections can be prevented by proper personal hygiene and by drinking plenty of fluids; they can be treated with antibiotic therapy.
			iii.	Urinary tract infections can lead to pyelonephritis or prostatitis.
9.2 Kidneys (p. 187, Fig. 9.4)
	1.	The kidney is divided into three regions: the renal cortex, renal medulla, and renal pelvis. A kidney contains over 1 million nephrons.
	2.	Anatomy of a Nephron (p. 188, Fig. 9.5)
		a.	Blood leads to the nephron via the renal artery and then the afferent arteriole that leads to the glomerulus of each nephron. Blood exits via the efferent arteriole and peritubular capillaries, leaving the kidney through the renal vein.
		b.	Nephron Has Several Parts (p. 189, Fig. 9.6)
			i.	The start of the nephron is the glomerular capsule that encloses the glomerulus, through which glomerular filtration occurs.
			ii.	The proximal convoluted tubule is next, with an interior brush border of microvilli that enhances tubular reabsorption.
			iii.	The nephron loop then dips down into the renal medulla and curves back up into the cortex, making the loop of the nephron (loop of Henle). 
			iv.	The distal convoluted tubule is adapted for tubular secretion, the active transport of materials from the blood into the filtrate.
			v.	The collecting duct represents the merger of several distal convoluted tubules and conveys urine to the renal pelvis.
9.3 Urine Formation (p. 190, Fig. 9.7)
	1.	Glomerular Filtration Divides the Blood (p. 190)
		a.	Glomerular filtration occurs as blood pressure drives the fluid portions of blood to be removed at the glomerular capsule.
		b.	Glomerular filtrate consists of fluids and molecules, similar to plasma.
		c.	About 180 liters of fluid are filtered per day, with the majority being reabsorbed.
	2.	Tubular Reabsorption Is Both Passive and Active (p. 191)
		a.	Tubular reabsorption in the proximal convoluted tubule occurs as ions, such as sodium, are actively transported back into the peritubular capillary, while other ions, such as chloride, follow passively.
		b.	The amount of a substance that is reabsorbed depends on the number of carrier molecules available for it. 
	3.	Tubular Secretion Adds Substances (p. 191, Table 9.2)
		Hydrogen and ammonium ions, creatinine, and medications such as penicillin are actively secreted into the distal convoluted tubule.
		HEALTH FOCUS: Spare Parts (p. 192, Fig. 9B)
		i.	Organ transplantations are now possible due to immunosuppressive drugs and the ability to preserve organs to be transplanted.
		ii.	When a donor dies, as many as 25 different organs and tissues can be removed for donation.
		iii.	The number of people waiting for organs is considerably greater than the number of donors.
9.4 Regulatory Functions of the Kidneys (p. 193)
	1.	Reabsorbing Water (p. 193, Fig. 9.8)
		a.	More than 99% of water is reabsorbed and returned to the blood.
		b.	Water reabsorption occurs because of the countercurrent mechanism, in which an osmotic gradient builds up in the renal medulla, drawing water out of the filtrate.
		c.	Antidiuretic hormone (ADH) from the posterior pitutary acts on the collecting duct to increase water reabsorption.
	2.	Reabsorbing Salt (p. 194, Fig. 9.9)
		a.	As much as 99% of sodium is reabsorbed from filtrate and returned to the blood. Most is reabsorbed at the proximal convoluted tubule, with the distal convoluted tubule and collecting duct absorbing the rest.
		b.	The juxtaglomerular apparatus secretes renin when blood pressure is insufficient to drive filtration. Renin converts angiotensin (from the liver) to angiotensin I. This is later converted to angiotension II, which stimulates the adrenal cortex to release aldosterone. Aldosterone promotes sodium reabsorption, increasing blood volume and pressure.
		c.	The heart secretes atrial natriuretic hormone when blood volume is too high. This inhibits the release of renin, and thus aldosterone.
		d.	Diuretics (p. 195) Diuretics increase urine output, decreasing blood volume and pressure.
	3.	Maintaining Blood pH (p. 195, Fig. 9.11)
		Nephrons excrete extra hydrogen and ammonium ions, and reabsorb sodium and bicarbonate ions to regulate blood pH.
9.5 Working Together (p. 197)
	The Working Together box (p. 196) illustrates how the urinary system works with other body systems to maintain homeostasis.
9.6 Other Excretory Organs (p. 197, Fig. 9.12)
	1.	Lungs Remove CO2 (p. 197) 
		During respiration, the lungs remove CO2 from the blood.
	2.	Skin Perspires (p. 197)
		a.	The sweat glands perspire, giving off salt, urea, and water.
		b.	During kidney failure, sweat glands give off more urea.
	3.	Liver Makes Bile Pigments (p. 197)
		a.	Bile pigments form during the breakdown of hemoglobin. 
		b.	Urochrome, the pigment that causes urine to be yellow, is a breakdown product of hemoglobin that is deposited in blood and later removed by the kidneys.
9.7 Problems with Kidney Function (p. 197)
	1.	Glomerular damage can lead to blocked glomeruli, or the glomeruli can become too permeable, allowing blood cells to be passed in the urine. When two-thirds of nephrons cannot function, wastes accumulate in the blood, leading to uremia.
	2.	Replacing the Kidney (p. 197)
		Kidney transplants are successful, especially when the donor is a close relative.
	3.	Dialysis: Treating Blood (p. 198, Fig. 9.13)
		a.	While awaiting a kidney transplant, a patient can undergo one of two types of dialysis.
		b.	Hemodialysis involves filtering the patient's blood through a semipermeable membrane into dialysis solution. 
		c.	Continuous ambulatory peritoneal dialysis (CAPD) uses dialysate introduced into the peritoneal cavity. Wastes transfer into the solution, which is removed 4 to 8 hours later.