Biology Excretory System Overview

Questions and Answers

What is the primary function of the kidneys in the excretory system?

Eliminating urine and regulating water and salt concentration (correct)

Removing carbon dioxide from the blood

Detoxifying ingested poisons

Eliminating sweat through the skin

Which of the following excretory organs primarily removes carbon dioxide from the blood?

Lungs (correct)

Liver

Kidneys

Skin

What is mainly excreted by the sweat glands in the skin?

Calcium and iron

Sodium chloride and water (correct)

Metabolic wastes and potassium

Nitrogenous wastes and urea

Which substance is formed from the deamination of proteins in the liver?

Urea Signup and view all the answers

Which excretory organ is responsible for eliminating excess inorganic substances through the feces?

Alimentary canal Signup and view all the answers

What is the filtrate primarily composed of?

Water and useful substances Signup and view all the answers

What is the main process required to convert filtrate into urine?

Selective reabsorption and excretion Signup and view all the answers

What type of capillaries make up the glomerulus?

Network of fenestrated capillaries Signup and view all the answers

What role do special cells in the Bowman’s capsule play?

To allow substances to pass through Signup and view all the answers

Which feature of the afferent arteriole aids in the filtration process?

Wider lumen Signup and view all the answers

What is the shape of the Bowman’s capsule and its significance?

Cup-shaped to increase surface area Signup and view all the answers

What network surrounds the proximal convoluted tubules for selective reabsorption?

Blood capillary network Signup and view all the answers

What is primarily removed from the body through the excretion process?

Urea and excess minerals Signup and view all the answers

What is the primary function of the urethra?

To transport urine out of the body. Signup and view all the answers

Which component primarily carries oxygenated blood to the kidneys?

Renal artery Signup and view all the answers

Which part of the kidney is responsible for processing the majority of the filtrate?

Cortex Signup and view all the answers

What role does the Malpighian body serve in the kidney?

It filters blood at the nephron level. Signup and view all the answers

What is the key difference between afferent and efferent arterioles?

Afferent arterioles carry blood to the glomerulus. Signup and view all the answers

What process describes the movement of substances from the renal tubules back into the bloodstream?

Active reabsorption Signup and view all the answers

During which condition is ADH secreted to increase water reabsorption in the kidneys?

Dehydration Signup and view all the answers

Which part of the nephron is primarily involved in the initial filtration of blood?

Bowman’s capsule Signup and view all the answers

What type of reabsorption often occurs against the concentration gradient?

Active reabsorption Signup and view all the answers

What structures in cuboidal cells increase the surface area for reabsorption?

Microvilli Signup and view all the answers

Which process does NOT require energy for reabsorption?

Diffusion Signup and view all the answers

What is primarily reabsorbed in the loop of Henle?

Water Signup and view all the answers

What type of molecules are actively excreted into the distal convoluted tubule?

Large wastes like creatinine Signup and view all the answers

Which ions does the distal tubule regulate to affect blood pH?

H+ ions and bicarbonate ions Signup and view all the answers

What characteristic of desert animals like camels allows them to conserve water effectively?

Wider renal medulla Signup and view all the answers

Which substances are NOT retained during the reabsorption process?

Excess vitamins Signup and view all the answers

What happens when there is an increase in ADH secretion?

More water is reabsorbed into the blood. Signup and view all the answers

What results from a high concentration of water in the blood?

Decreased permeability of distal tubule to water. Signup and view all the answers

Which nitrogenous waste is eliminated by the kidneys?

Urea Signup and view all the answers

Which process is involved in maintaining the blood's pH level?

Secretion of H+ or bicarbonate ions. Signup and view all the answers

What is the role of the kidneys in osmoregulation?

Retention or elimination of water. Signup and view all the answers

What is NOT a function of the kidneys?

Regulation of blood sugar. Signup and view all the answers

How do the kidneys and pituitary gland interact to maintain water content?

By adjusting ADH levels. Signup and view all the answers

What characterizes the urine produced when less water is reabsorbed?

It has a larger volume. Signup and view all the answers

Study Notes

Excretory Organs and Homeostasis

Excretory organs maintain optimal internal state by removing metabolic wastes and regulating water balance (osmoregulation).
They play a critical role in homeostasis, ensuring cell survival within a controlled environment.

Main Excretory Organs

Kidneys: Eliminate urine, which consists of excess water, salts, and nitrogenous wastes; regulate water and salt concentration in the body.
Lungs: Remove carbon dioxide from the blood through diffusion at the alveoli.
Skin: Sweat glands eliminate sweat, containing water, salts (mainly sodium chloride), and some nitrogenous wastes, but in lower concentration than urine.
Liver: Eliminates cellular wastes, processes hemoglobin from red blood cells, deaminates proteins to form urea, and detoxifies ingested poisons.
Alimentary Canal: Excretes metabolic wastes and excess inorganic substances into the large intestine, which are eliminated as feces along with a filtrate that contains useful substances and waste.

Structural Features of the Malpighian Body

Glomerulus: A network of capillaries that increases surface area for ultra-filtration; walls are thin to allow substance passage, and arterioles create pressure for efficient filtration.
Bowman’s Capsule: Has a cup shape to increase surface area; consists of a single layer of epithelial cells for easy passage of substances.

Selective Reabsorption

Useful substances are reabsorbed from proximal convoluted tubules into surrounding capillaries, involving both active (energy-consuming) and passive (energy-free) transport.
Active reabsorption often occurs against the concentration gradient using carrier molecules; cells possess many mitochondria for energy.
The presence of microvilli increases surface area for efficient reabsorption; water reabsorption primarily occurs through osmosis.
Excess vitamins/minerals are not reabsorbed if levels exceed physiological capacity; the loop of Henle optimizes water conservation, especially in desert animals.

Tubular Excretion

At the distal convoluted tubule, large wastes (e.g., creatinine) are actively excreted; smaller wastes like urea passively exit the blood.
Drug elimination occurs, and the distal tubule regulates blood pH by managing H+ and bicarbonate ions.
The release of antidiuretic hormone (ADH) influences water permeability in tubules, adjusting urine concentration depending on blood water levels.

Functions of the Kidneys

Excretion: Removes nitrogenous wastes like urea and uric acid.
Osmoregulation: Maintains normal salt and water levels in the blood.
pH Control: Regulates pH by excreting H+ or bicarbonate ions to keep blood slightly alkaline.
Toxin Control: Eliminates some ingested poisons.

Implications for Homeostasis

Kidneys control chemical balance between the body and environment through osmoregulation, affecting blood volume and intercellular fluid levels, crucial for cell function.

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Description

Explore the functions and importance of the excretory organs in maintaining homeostasis in the body. This quiz covers the main excretory organs like kidneys and lungs, focusing on their roles in waste removal and osmoregulation. Test your knowledge on how these organs contribute to the optimal internal environment for cellular survival.