1. Presentation title slide

2. UNIT B: Human Body Systems
Chapter 8: Human Organization
Chapter 9: Digestive System
Chapter 10: Circulatory System and Lymphatic System
Chapter 11: Respiratory System
Chapter 12: Nervous System
Chapter 13: Urinary System: Section 13.1
Chapter 14: Reproductive System

3. 13.1 The Urinary System UNIT B
Chapter 13: Urinary System
Section 13.1
13.1 The Urinary System
The urinary system is involved in excretion, which is the removal of metabolic wastes from the body.
The urinary system produces urine and conducts it outside the body.
urinary system: a type of organ system containing the kidneys, the urinary bladder, and the tubes that carry urine; eliminates metabolic wastes from the body and helps regulate the fluid balance and pH of the blood
excretion: the removal of metabolic wastes from the body
urine: liquid waste produced by the kidneys and excreted from the body
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4. Functions of the Urinary System
UNIT B
Chapter 13: Urinary System
Section 13.1
Functions of the Urinary System
Excretion of Metabolic Wastes
The kidneys excrete metabolic wastes (mostly nitrogenous wastes: urea, ammonium, creatinine, uric acid)
Urea is formed when ammonia released during amino acid breakdown combines with CO2
Some ammonia (NH3) is excreted as ammonium ion (NH4+)
Creatinine is a breakdown product of creatine phosphate, a high-energy phosphate reserve molecule
Uric acid is produced from the breakdown of nucleotides
Gout can occur if too much uric acid in the blood has crystallized and moved into the joints
urea: a by-product of amino acid metabolism
ammonia: a product of the breakdown of amino acids in the liver; extremely toxic
uric acid: produced by the breakdown of nucleotides
gout: a painful ailment caused by too much uric acid in the blood, which forms crystals and precipitates out in the joints
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5. UNIT B
Chapter 13: Urinary System
Section 13.1
Osmoregulation
The kidneys are involved in osmoregulation (maintenance of the balance of water and salt in the blood)
Salts can cause osmosis (diffusion of water) into the blood, causing blood volume and blood pressure to increase
Kidneys also maintain levels of other ions, such as potassium (K+), bicarbonate (HCO3-), and calcium (Ca2+), in the blood
Regulation of Acid-Base Balance
The kidneys help regulate the acid-base balance of the blood
Monitor and keep blood pH at 7.4 by excreting hydrogen ions (H+) and reabsorbing bicarbonate ions (HCO3-)
osmoregulation: the maintenance of the appropriate balance of water and salt in the blood
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6. UNIT B Secretion of Hormones
Chapter 13: Urinary System
Section 13.1
Secretion of Hormones
The kidneys help the endocrine system in hormone secretion
Secrete renin, an enzyme that stimulates the adrenal cortex to secrete the hormone aldosterone, which promotes the absorption of sodium ions (Na+) by the kidneys
Secrete the hormone erythropoietin (EPO) to simulate red blood cell production when oxygen demand increases
Help activate Vitamin D, a hormone-like molecule that promotes calcium (Ca2+) absorption from the digestive tract
erythropoietin (EPO): a hormone secreted by the kidneys that stimulates red blood cell production
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7. Organs of the Urinary System
UNIT B
Chapter 13: Urinary System
Section 13.1
Organs of the Urinary System
The urinary system consists of the kidneys, ureters, urinary bladder, and urethra.
Figure 13.1 The urinary system. Urine is found only within the kidneys, the ureters, the urinary bladder, and the urethra. The kidneys are important organs of homeostasis because they excrete metabolic wastes and adjust both the water–salt and acid–base balance of the blood.
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8. UNIT B
Chapter 13: Urinary System
Section 13.1
Kidneys
Paired, bean-shaped organs that regulate acid-base balance and water-salt balance of blood
Each kidney is covered by a tough connective tissue layer called a renal capsule
Each kidney has a depression (called a hilium) on the concave side where a renal artery enters and a renal vein and ureter exit
kidneys: paired organs of the urinary system that regulate the chemical composition of the blood and produce a waste product called urine
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9. UNIT B
Chapter 13: Urinary System
Section 13.1
Ureters
Small muscular tubes that transport urine from the kidneys to the bladder
Wall of each ureter has three layers: inner mucosa, smooth muscle layer, outer fibrous connective tissue
Peristaltic contractions in the ureters cause urine to enter the bladder
ureters: small, muscular tubes that conduct urine from the kidneys to the bladder
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10. Urinary Bladder UNIT B Stores urine until it is expelled from the body
Chapter 13: Urinary System
Section 13.1
Urinary Bladder
Stores urine until it is expelled from the body
Has three openings: two for the ureters, and one for the urethra, which drains the bladder
Has two sphincters that lie close to where the urethra exits the bladder
External sphincter is under voluntary control
urinary bladder: part of the urinary system that stores urine until it is expelled from the body
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11. UNIT B
Chapter 13: Urinary System
Section 13.1
Urethra
Small tube opening that extends from the bladder to an external opening
Removes urine from the body
Males: 20 cm long; urethra carries urine and semen
Females: 4 cm long; urethra carries urine (not connected to reproductive system)
urethra: a small tube that extends from the urinary bladder to an external opening that removes urine from the body; in the male reproductive system, it connects to the ejaculatory ducts
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12. UNIT B
Chapter 13: Urinary System
Section 13.1
Urination
When the bladder fills with about 250 mL of urine, stretch receptors send nerve impulses to the spinal cord
Motor nerve impulses from the spinal cord cause the bladder to contract and sphincters to relax, allowing urination to occur
The brain controls this reflex in older children and adults, allowing urination to be delayed
Figure 13.2 Urination. As the bladder fills with urine, sensory impulses go to the spinal cord and then to the brain. When urination occurs, motor nerve impulses cause the bladder to contract and internal and external sphincters to relax.
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13. Check Your Progress UNIT B Define excretion.
Chapter 13: Urinary System
Section 13.1
Check Your Progress
Define excretion.
Describe the functions of the urinary system.
Describe a function of the kidneys.
ANSWERS
1. Excretion is the removal of liquid metabolic wastes.
2. The four major functions of the urinary system are excretion of wastes, maintenance of water–salt balance (osmoregulation), maintenance of acid–base balance, and secretion of hormones.
3. The kidneys produce urine, which contains metabolic wastes such as urea and uric acid, and maintain osmotic balance, blood volume, blood pressure, and acid–base balance. The kidneys also produce renin and erythropoietin and activate vitamin D.
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14. UNIT B
Chapter 13: Urinary System
Section 13.1
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15. UNIT B
Chapter 13: Urinary System
Section 13.1
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