Urinary System Functions

The Urinary System

• Consists of: 2 kidneys, 2 ureters, bladder, and urethra
• Primary role: Ensure optimal blood properties, regulate water and electrolyte balance, and excrete metabolic wastes and bioactive substances

Functions of the Urinary System

• Regulate water and electrolyte balance
• Excrete metabolic wastes, excess water, and electrolytes in urine
• Excrete bioactive substances, including drugs
• Secretion of renin, erythropoietin, and vitamin D
• Maintain pH levels and regulate blood pressure

Kidneys

• Covered by a thin fibrous layer, with an outer layer of fibroblasts and collagen fibers, and an inner layer of myofibroblasts
• Hilum: where nerves enter and ureter exits
• Renal pelvis: divides into 2-3 major calyces, which then turn into minor calyces
• Renal cortex: outer darker region containing renal corpuscles and tubules
• Renal medulla: inner region consisting of aligned linear tubules and ducts
• Renal pyramids: 8-15, with bases meeting at the cortex by the corticomedullary junction

Nephron

• Functional unit that filters blood and forms urine
• Consists of a renal corpuscle and a long renal tubule
• Renal corpuscle: glomerulus and Bowman's capsule
• Glomerulus: a tuft of capillaries where blood filtration begins
• Bowman's capsule: a double-walled capsule that surrounds the glomerulus and collects the filtrate

Renal Tubule

• Divided into several segments, each with specific functions in processing the filtrate
• Proximal convoluted tubule (PCT): reabsorbs a majority of the filtrate, including water, ions, and nutrients
• Loop of Henle: a U-shaped structure that extends into the medulla
• Distal convoluted tubule (DCT): continues to reabsorb ions and water, under the influence of hormones
• Collecting duct: the final segment that receives filtrate from multiple nephrons

Nephron Functions

• Filtration: occurs in the renal corpuscle, where blood pressure forces water and small solutes through the glomerular capillary walls
• Tubular reabsorption: substances are transported from the tubular fluid back into the blood
• Tubular secretion: substances are transported from the blood into the tubular fluid

Blood Flow in the Kidneys

• Renal arteries: transport oxygenated blood from the heart and aorta to the kidneys
• Renal veins: transport filtered deoxygenated blood from the kidneys to the heart
• Interlobular arteries: radiate from the arcuate arteries, extending deep into the cortex
• Afferent arterioles: lead into the glomerulus, and efferent arterioles exit from the glomerulus

Renal Corpuscle

• Contains a tuft of capillaries called glomerulus, surrounded by a epithelial capsule called the glomerular capsule
• Glomerular capsule: has a visceral layer and a parietal layer, with a capsular space between them
• Podocytes: stellate epithelium that creates the filtration apparatus of the kidney
• Slit pores: regulate the passage of substances during filtration

Proximal Convoluted Tubule (PCT)

• Cells are highly specialized for reabsorption and secretion
• Structure: dense brush border, abundant mitochondria, and extensive membrane invaginations
• Function: reabsorbs a majority of the filtrate, including water, ions, and nutrients

Loop of Henle

• Located in the medulla
• Thin descending limb and thin ascending limb: simple squamous epithelium and organelles
• Thick ascending limb: simple cuboidal epithelium and many mitochondria

Distal Convoluted Tubule (DCT)

• Lined with simple cuboidal cells that are smaller and flatter compared to the ones in the PCT
• Function: performs regulated reabsorption while influenced by the hormone aldosterone

Ureters

• Muscular tubes that transport urine from the renal pelvis to the urinary bladder
• Structure: mucosa, muscularis, and adventitia
• Function: move urine towards the bladder via peristaltic contractions and prevent backflow into the kidneys

Urinary Bladder

• Structure: mucosa, muscularis, and adventitia
• Function: stores urine and expels it during micturition

Urothelium (Transitional Epithelium)

• Found in the renal pelvis, ureters, bladder, and parts of the urethra
• Structure: basal cells, intermediate cells, and umbrella cells
• Function: protects underlying tissues from the toxic effects of urine and allows the bladder to stretch and contract

Urethra

• Structure: varies in males and females, but includes a prostatic urethra, membranous urethra, and spongy urethra
• Function: conducts urine from the bladder to the exterior, and in males, serves as a conduit for semen during ejaculation

The Urinary System

• Consists of: 2 kidneys, 2 ureters, bladder, and urethra
• Primary role: Ensure optimal blood properties, regulate water and electrolyte balance, and excrete metabolic wastes and bioactive substances

Functions of the Urinary System

• Regulate water and electrolyte balance
• Excrete metabolic wastes, excess water, and electrolytes in urine
• Excrete bioactive substances, including drugs
• Secretion of renin, erythropoietin, and vitamin D
• Maintain pH levels and regulate blood pressure

Kidneys

• Covered by a thin fibrous layer, with an outer layer of fibroblasts and collagen fibers, and an inner layer of myofibroblasts
• Hilum: where nerves enter and ureter exits
• Renal pelvis: divides into 2-3 major calyces, which then turn into minor calyces
• Renal cortex: outer darker region containing renal corpuscles and tubules
• Renal medulla: inner region consisting of aligned linear tubules and ducts
• Renal pyramids: 8-15, with bases meeting at the cortex by the corticomedullary junction

Nephron

• Functional unit that filters blood and forms urine
• Consists of a renal corpuscle and a long renal tubule
• Renal corpuscle: glomerulus and Bowman's capsule
• Glomerulus: a tuft of capillaries where blood filtration begins
• Bowman's capsule: a double-walled capsule that surrounds the glomerulus and collects the filtrate

Renal Tubule

• Divided into several segments, each with specific functions in processing the filtrate
• Proximal convoluted tubule (PCT): reabsorbs a majority of the filtrate, including water, ions, and nutrients
• Loop of Henle: a U-shaped structure that extends into the medulla
• Distal convoluted tubule (DCT): continues to reabsorb ions and water, under the influence of hormones
• Collecting duct: the final segment that receives filtrate from multiple nephrons

Nephron Functions

• Filtration: occurs in the renal corpuscle, where blood pressure forces water and small solutes through the glomerular capillary walls
• Tubular reabsorption: substances are transported from the tubular fluid back into the blood
• Tubular secretion: substances are transported from the blood into the tubular fluid

Blood Flow in the Kidneys

• Renal arteries: transport oxygenated blood from the heart and aorta to the kidneys
• Renal veins: transport filtered deoxygenated blood from the kidneys to the heart
• Interlobular arteries: radiate from the arcuate arteries, extending deep into the cortex
• Afferent arterioles: lead into the glomerulus, and efferent arterioles exit from the glomerulus

Renal Corpuscle

• Contains a tuft of capillaries called glomerulus, surrounded by a epithelial capsule called the glomerular capsule
• Glomerular capsule: has a visceral layer and a parietal layer, with a capsular space between them
• Podocytes: stellate epithelium that creates the filtration apparatus of the kidney
• Slit pores: regulate the passage of substances during filtration

Proximal Convoluted Tubule (PCT)

• Cells are highly specialized for reabsorption and secretion
• Structure: dense brush border, abundant mitochondria, and extensive membrane invaginations
• Function: reabsorbs a majority of the filtrate, including water, ions, and nutrients

Loop of Henle

• Located in the medulla
• Thin descending limb and thin ascending limb: simple squamous epithelium and organelles
• Thick ascending limb: simple cuboidal epithelium and many mitochondria

Distal Convoluted Tubule (DCT)

• Lined with simple cuboidal cells that are smaller and flatter compared to the ones in the PCT
• Function: performs regulated reabsorption while influenced by the hormone aldosterone

Ureters

• Muscular tubes that transport urine from the renal pelvis to the urinary bladder
• Structure: mucosa, muscularis, and adventitia
• Function: move urine towards the bladder via peristaltic contractions and prevent backflow into the kidneys

Urinary Bladder

• Structure: mucosa, muscularis, and adventitia
• Function: stores urine and expels it during micturition

Urothelium (Transitional Epithelium)

• Found in the renal pelvis, ureters, bladder, and parts of the urethra
• Structure: basal cells, intermediate cells, and umbrella cells
• Function: protects underlying tissues from the toxic effects of urine and allows the bladder to stretch and contract

Urethra

• Structure: varies in males and females, but includes a prostatic urethra, membranous urethra, and spongy urethra
• Function: conducts urine from the bladder to the exterior, and in males, serves as a conduit for semen during ejaculation

The Urinary System

• Consists of: 2 kidneys, 2 ureters, bladder, and urethra
• Primary role: Ensure optimal blood properties, regulate water and electrolyte balance, and excrete metabolic wastes and bioactive substances

Functions of the Urinary System

• Regulate water and electrolyte balance
• Excrete metabolic wastes, excess water, and electrolytes in urine
• Excrete bioactive substances, including drugs
• Secretion of renin, erythropoietin, and vitamin D
• Maintain pH levels and regulate blood pressure

Kidneys

• Covered by a thin fibrous layer, with an outer layer of fibroblasts and collagen fibers, and an inner layer of myofibroblasts
• Hilum: where nerves enter and ureter exits
• Renal pelvis: divides into 2-3 major calyces, which then turn into minor calyces
• Renal cortex: outer darker region containing renal corpuscles and tubules
• Renal medulla: inner region consisting of aligned linear tubules and ducts
• Renal pyramids: 8-15, with bases meeting at the cortex by the corticomedullary junction

Nephron

• Functional unit that filters blood and forms urine
• Consists of a renal corpuscle and a long renal tubule
• Renal corpuscle: glomerulus and Bowman's capsule
• Glomerulus: a tuft of capillaries where blood filtration begins
• Bowman's capsule: a double-walled capsule that surrounds the glomerulus and collects the filtrate

Renal Tubule

• Divided into several segments, each with specific functions in processing the filtrate
• Proximal convoluted tubule (PCT): reabsorbs a majority of the filtrate, including water, ions, and nutrients
• Loop of Henle: a U-shaped structure that extends into the medulla
• Distal convoluted tubule (DCT): continues to reabsorb ions and water, under the influence of hormones
• Collecting duct: the final segment that receives filtrate from multiple nephrons

Nephron Functions

• Filtration: occurs in the renal corpuscle, where blood pressure forces water and small solutes through the glomerular capillary walls
• Tubular reabsorption: substances are transported from the tubular fluid back into the blood
• Tubular secretion: substances are transported from the blood into the tubular fluid

Blood Flow in the Kidneys

• Renal arteries: transport oxygenated blood from the heart and aorta to the kidneys
• Renal veins: transport filtered deoxygenated blood from the kidneys to the heart
• Interlobular arteries: radiate from the arcuate arteries, extending deep into the cortex
• Afferent arterioles: lead into the glomerulus, and efferent arterioles exit from the glomerulus

Renal Corpuscle

• Contains a tuft of capillaries called glomerulus, surrounded by a epithelial capsule called the glomerular capsule
• Glomerular capsule: has a visceral layer and a parietal layer, with a capsular space between them
• Podocytes: stellate epithelium that creates the filtration apparatus of the kidney
• Slit pores: regulate the passage of substances during filtration

Proximal Convoluted Tubule (PCT)

• Cells are highly specialized for reabsorption and secretion
• Structure: dense brush border, abundant mitochondria, and extensive membrane invaginations
• Function: reabsorbs a majority of the filtrate, including water, ions, and nutrients

Loop of Henle

• Located in the medulla
• Thin descending limb and thin ascending limb: simple squamous epithelium and organelles
• Thick ascending limb: simple cuboidal epithelium and many mitochondria

Distal Convoluted Tubule (DCT)

• Lined with simple cuboidal cells that are smaller and flatter compared to the ones in the PCT
• Function: performs regulated reabsorption while influenced by the hormone aldosterone

Ureters

• Muscular tubes that transport urine from the renal pelvis to the urinary bladder
• Structure: mucosa, muscularis, and adventitia
• Function: move urine towards the bladder via peristaltic contractions and prevent backflow into the kidneys

Urinary Bladder

• Structure: mucosa, muscularis, and adventitia
• Function: stores urine and expels it during micturition

Urothelium (Transitional Epithelium)

• Found in the renal pelvis, ureters, bladder, and parts of the urethra
• Structure: basal cells, intermediate cells, and umbrella cells
• Function: protects underlying tissues from the toxic effects of urine and allows the bladder to stretch and contract

Urethra

• Structure: varies in males and females, but includes a prostatic urethra, membranous urethra, and spongy urethra
• Function: conducts urine from the bladder to the exterior, and in males, serves as a conduit for semen during ejaculation