Excretory System: The Urinary System and Homeostatsis

What organ is mainly responsible for urinary homeostasis?

The kidneys are mainly responsible for urinary homeostasis by regulating water, electrolytes, and waste products in the blood.

What is the process called when urine is expelled from the body?

Excretion

In what ways does the urinary system maintain homeostasis?

1. Regulation of blood levels of ions → Na, K, Cl, Ca

2. Regulation of water content in blood

3. Helps maintain the proper blood pH

4. Retention of important nutrients → Glucose, Amino Acids

5. Secretion of hormones

6. Elimination of cellular waste products → Urea

What is urea?

The product of amino acid metabolism

How is urea formed?

Urea is formed through the liver's deamination process, where amino groups are removed from amino acids, converting them into ammonia, which is then converted to urea for excretion

What filters urea?

The kidneys filter urea from the blood during the process of urine formation utilizing nephrons to separate waste.

What shape is a kidney?

Bean-shaped organs located on either side of the spinal cord, extending slightly from waist

Where do cellular wastes enter?

Through a renal artery

Where does blood exit after filteration?

Through a renal vein

Where does urine leave the kidney through?

A narrow, muscular tube called a ureter

How many ureters does a human have?

2

Where do the ureters transport the urine to?

The bladder

What organ collects and storers urine?

The bladder

What do the walls of the bladder contain?

Smooth muscle that allows for stretching and contractionto accommodate urine volume

What retains urine?

Sphincter muscles (2x)

Are the sphincter muscles voluntary?

No, the first one isn’t; second one is

How much urine can an average adult hold?

1 pint

What passageway does the urine use to leave the body?

The urethra

1.5 inch - female

8 inches - male

What is the outermost layer of a kidney where urine is formed

Renal cortex

What is the second most outward layer of the kidney

The renal medulla

What is the innermost layer of where urine is formed in the kidney

The renal pelvis

What is the glomerulus?

A dense knot of capillaries that filters blood to form urine, located in the nephron

What is the Bowman’s capsule?

A cup-shaped structure that encases the glomerulus, collecting the filtrate formed during blood filtration in the kidney

What does the proximal convoluted tube act as

the primary site for reabsorption of water, ions, and nutrients from the filtrate in the nephron

What is the loop of Henle and location

The loop of Henle is a U-shaped tube in the nephron that extends into the medulla of the kidney, playing a crucial role in concentrating urine by reabsorbing water and salts

What hormone plays a role in concentration of urine

Antidiuretic hormone (ADH)

What is the distal convoluted tubule primary use?

Nutrients are selectively reabsorbed from the filtrate back into the blood and eventually leads to the collecting duct

What does blood filtration in the glomerulus?

(blood) pressure

What do kidneys regulate

Water content of the blood

What is water reabsorption controlled by?

Negative feedback → ADH

What is the result of higher ADH hormone in the blood?

More reabsorption → concentrated urine

What is the result of lower ADH hormone in the blood?

Less reabsorption → dilute urine

What else do the kidney regulate?

Blood pressure and oxygen content of the blood via kidney hormones

How is blood conducted to each nephron

through afferent arterioles that branch from the renal artery

What are the walls of the glomerulus extremely permeable to?

water, ions, and small molecules

What do the capillaries form when they reunite

efferent arterioles that carry blood away from the glomerulus

What is a key difference between the afferent and efferent arteriole?

The afferent arteriole supplies blood to the glomerulus, while the efferent arteriole carries blood away from it, returning it to the circulation AND the efferent arteriole is smaller in diameter

How does the diameter of the efferent arteriole play a role in homeostasis

It creates pressure within the glomerulus, driving water and many of the dissolved substances from the blood through the capillary walls

What is the process of filtration?

The process whereby water and solutes are forced from the blood in the glomerulus into the Bowman's capsule due to pressure differences.

What is collected in the Bowman’s Capsule

Mixture of wastes, essential nutrients, and water

What is tubular reabsorption

The process by which cells of the tuble remove water and nutrients from the filtrate and pass them back to the blood

What type of transport is tubular reabsorption

Primarily active transport, with some passive transport involved.

How does osmosis play a role?

Osmosis plays a role by allowing water to move from areas of low solute concentration in the renal tubules to areas of high solute concentration in the blood, facilitating the reabsorption of water and maintaining fluid balance.

What is tubular secretion

The process by which wastes and excess substances that were not initially filtered into Bowmans capsule are removed form the blood for excretion

What type of transport is primarily used in tubular secretion?

Tubular secretion primarily utilizes active transport to move substances from the blood into the renal tubules for excretion.

What does the ability to concentrate urine depend on?

structure of both the nephron and collecting duct into which the nephrons empty

What are all 5 parts of the kidney outside in

the renal capsule, renal cortex, renal medulla, renal pelvis, and ureter.

How does the liver deal with ammonium

The liver converts ammonium to urea through the urea cycle, which is then eliminated from the body via urine.

What type of contractions transport the urine to the bladder

reflexive contractions

What are all parts of the nephron

The nephron consists of the glomerulus, Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.

What are peritubular capillaries

Peritubular capillaries are small blood vessels that surround the nephron's tubules, facilitating the reabsorption of water and nutrients from the filtrate back into the bloodstream

What part of the nephron allows the urine to become concentrated

The loop of Henle