Biology Chapter: Waste Excretion & Internal Equilibrium

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Questions and Answers

Which substance is NOT filtered through the glomerulus into Bowman’s capsule?

Urea

Proteins (correct)

Water

Glucose

Most of the water that enters the nephrons is reabsorbed back into the bloodstream.

True

What process occurs in the Loop of Henle to promote water reabsorption?

Osmosis

Na+ ions are actively transported out of the nephron, causing _____ to follow by passive transport.

water Signup and view all the answers

Match the following processes with their descriptions:

Filtration = Movement of water and solutes into Bowman’s capsule Reabsorption = Transport of substances from nephron back to blood Secretion = Transport of substances from blood into urine Active Transport = Uses energy to move substances against a gradient Signup and view all the answers

Which hormone is known to significantly affect renal function?

Aldosterone Signup and view all the answers

All glucose and amino acids are completely reabsorbed by the nephrons.

False Signup and view all the answers

What is the expected result when there is a higher concentration of solutes in the blood than in the nephron?

Water will move from nephron to blood Signup and view all the answers

What substance is formed from the breakdown of excess protein in the liver?

Ammonia Signup and view all the answers

The kidneys are responsible for controlling the body's water balance.

True Signup and view all the answers

What is the name of the functional units of the kidney?

nephrons Signup and view all the answers

Urea is formed in the liver by combining CO2 with _____ .

ammonia Signup and view all the answers

Match the parts of the nephron with their functions:

Bowman's Capsule = Houses the glomerulus Glomerulus = Site of blood filtration Proximal tubule = Reabsorption of nutrients Loop of Henle = Concentration of urine Signup and view all the answers

What is the pathway of blood after it leaves the glomerulus?

To the efferent arterioles Signup and view all the answers

The bladder sends a signal to the brain only when it is full.

True Signup and view all the answers

What is created during the breakdown of nucleic acids?

uric acid Signup and view all the answers

The renal arteries branch from the _____ to supply blood to the kidneys.

aorta Signup and view all the answers

What is the first step in the formation of urine?

Filtration Signup and view all the answers

Study Notes

Waste Excretion and Internal Equilibrium

Waste products, such as carbon dioxide, are excreted.
Other waste products come from various sources.
The liver converts toxins into less harmful substances and sends them to the kidneys for excretion.

Waste Products

Kidneys receive many substances.
Excess protein is converted to carbohydrates through a process called deamination.
The amino groups in protein form ammonia, a toxic substance sent to the kidneys.
The liver combines carbon dioxide with ammonia to create urea, which is sent to the kidneys.
Uric acid is formed during the breakdown of nucleic acids and sent to the kidneys.

Water Balance

Kidneys are crucial for regulating water balance.
Water is more important than food; loss requires replenishment (dehydration).
Without adequate water, death can occur within three days.

Anatomy of the Urinary System

Kidneys filter blood; 25% of blood can be within the kidneys.
Waste is filtered from the blood by the kidneys and sent to the bladder through ureters
Urine stays in the bladder until it becomes full.
A message is sent to the brain when the bladder is full, creating the urge to urinate.
The urinary sphincter relaxes, allowing urine to flow into the urethra.

Anatomy of the Kidney

The outer layer is termed the cortex.
The next layer in is termed the medulla.
Renal pelvis is a hollow tube that connects the kidney and the ureter.
Nephrons are functional units of the kidney.

Anatomy of the Nephron

Nephrons are the functional units in the kidneys.
Blood is supplied by afferent arteries.
Afferent arteries branch into capillary beds, also called glomeruli.
There's a single glomerulus.
The blood leaves the glomerulus, not to a vein, but rather an arteriole system called efferent arterioles (A comes before E in the alphabet).
The efferent arterioles form a capillary bed around the kidney tubule, called peritubular capillaries.
The peritubular capillaries join the renal vein.
Glomerulus is surrounded by Bowman's capsule which becomes the proximal tubule.
Proximal tubule becomes the Loop of Henle.
Loop of Henle becomes the distal tubule.
Distal tubule becomes the collecting duct.
In most nephrons, the loop of Henle is relatively short, within the cortex.
Some nephrons have a long loop of Henle, plunging into the medulla.

Formation of Urine

Three steps involved in urine formation:
Filtration,
Reabsorption, and
Secretion.

1. Filtration

The glomerulus (has high pressure capillaries) allows water and dissolved solutes to pass into the Bowman's capsule.
Cells platelets and proteins are too large to pass through.
Substances that fit through include water, salt (sodium chloride), glucose, amino acids, hydrogen ions, and urea.

2. Reabsorption

On average, 600ml of fluid flows through the kidney per minute.
1ml of this fluid becomes urine.
Reabsorption is done by both passive and active processes.
Active transport involves the movement of Na+ across membranes, with negative ions following; not all salt can be pumped out, as the nephron reaches a threshold level.
Glucose and amino acids are actively transported back into the bloodstream. Any excess remains in the urine.
Passive transport involves water diffusing to follow the high solute concentration in the blood; urea and uric acid also follow, but not as much as water.
Most water reabsorption happens in the Loop of Henle.
The ascending portion of the Loop of Henle actively pumps Na+ out into the blood, whilst the descending portion of the loop is hypotonic forcing the water out by osmosis. This also occurs in the collecting duct.

3. Secretion

Active transport moves substances into the urine by cells in the distal tubule.
These substances include NaCl, HCO3–,and K+ and H+.

Hormones That Affect Renal Function

ADH (Antidiuretic Hormone): Produced in the hypothalamus, released by the pituitary gland.
It acts on the collecting duct to increase water reabsorption.
The higher the ADH in the blood, the more water is reabsorbed; the urine becomes more concentrated.
Osmoreceptors detect osmotic pressure changes in the hypothalamus, which signals the pituitary to release ADH.
Aldosterone: Released by the adrenal glands. This hormone acts on the distal tubule and collecting duct to increase the active transport of Na+ back into the blood, this causes water to follow passively.
Has same effect as ADH in reducing urine production, but with differences.

Diuretics

Diuretics block the release of ADH.

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Description

This quiz focuses on the processes of waste excretion and the role of the kidneys in maintaining internal equilibrium. It covers topics such as the conversion of toxins by the liver, the formation of urea, and the significance of water balance in the body. Test your knowledge on how the urinary system functions and its importance in human biology.