Question

Match each structure with a function. _____ureter _____Bowman's capsule _____urethra _____collecting tubule _____pituitary _____gland a. start of nephron b. delivers urine to body surface c. carries urine from kidney to bladder d. secretes \(\mathrm{ADH}\) e. target of aldosterone

Short answer

Ureter (c), Bowman's capsule (a), Urethra (b), Collecting tubule (e), Pituitary gland (d).

Step-by-step solution

Understand Each Structure

- **Ureter**: A tube that carries urine from the kidney to the bladder. - **Bowman's Capsule**: The start of the nephron in the kidney, where blood filtration begins. - **Urethra**: A tube that carries urine from the bladder out of the body. - **Collecting Tubule**: Part of the nephron in the kidney where final urine concentration occurs. - **Pituitary Gland**: An endocrine gland that secretes hormones, such as Antidiuretic Hormone (ADH).

Match Structures to Functions

- **Ureter**: Matches with **(c) carries urine from kidney to bladder**. - **Bowman's Capsule**: Matches with **(a) start of nephron**. - **Urethra**: Matches with **(b) delivers urine to body surface**. - **Collecting Tubule**: Matches with **(e) target of aldosterone**. - **Pituitary Gland**: Matches with **(d) secretes ADH**.

Key concepts

Nephron Function

The nephron is the fundamental structural and functional unit of the kidney, playing a crucial role in maintaining homeostasis in the body. Nephrons have the essential job of filtering blood and forming urine. This intricate process involves several key steps:

• Filtration: This process takes place in the Bowman's capsule, where blood enters through the glomerulus. The blood pressure forces water and small molecules out of the blood and into the nephron.
• Reabsorption: As the filtrate passes through the nephron tubules, essential nutrients, water, and ions are reabsorbed back into the bloodstream, ensuring that the body retains necessary substances.
• Secretion: Additional waste products and excess ions are secreted into the tubule from the surrounding blood vessels, allowing for fine-tuning of the urine composition.
• Excretion: The final urine that remains in the collecting duct is transported to the bladder for elimination from the body.

These processes allow the kidney to control the body's fluid balance, electrolyte levels, and waste removal efficiently. Understanding how nephrons work is vital to grasping kidney function.

Hormonal Regulation in Kidneys

Hormones play a pivotal role in regulating kidney function. They ensure that the body's internal environment remains stable. Several hormones impact the kidneys significantly:

• Aldosterone: This hormone is secreted by the adrenal glands and acts on the distal tubules and collecting ducts. It stimulates sodium reabsorption, which leads to increased water retention, and consequently, higher blood pressure.
• Antidiuretic Hormone (ADH): Secreted by the pituitary gland, ADH increases water permeability in the collecting ducts, promoting water reabsorption into the bloodstream and concentrating the urine.
• Atrial Natriuretic Peptide (ANP): This hormone is released by the heart atria and works to decrease sodium reabsorption, which results in increased urine production and reduced blood volume and pressure.

These hormonal changes allow the kidneys to adjust to different physiological states such as dehydration or overhydration, maintaining optimal fluid balance and pressure in the body.

Anatomy of Excretory Organs

The excretory system is essential for removing waste products from the body to maintain efficiency and health. It comprises several key structures, each performing specific functions:

• Kidneys: These bean-shaped organs filter the blood, remove waste, and create urine in a process involving multiple nephrons.
• Ureters: Two narrow tubes that transport urine from each kidney to the bladder.
• Bladder: A hollow muscular organ that collects and stores urine until it is ready to be expelled.
• Urethra: The channel through which urine exits the body from the bladder, differing in length and structure between males and females.

Understanding the anatomy of these organs provides insights into how the body maintains homeostasis through waste elimination.

Endocrine System and ADH Secretion

The endocrine system is a network of glands that produce and release hormones. It affects many body processes, including those of the kidneys. A critical component of this system is the secretion of Antidiuretic Hormone (ADH):

• ADH Function: Also known as vasopressin, ADH is produced in the hypothalamus and stored in the posterior pituitary gland. It helps regulate water balance in the body by controlling the amount of water the kidneys reabsorb.
• Stimulus for ADH Release: When the body is dehydrated, plasma osmolarity increases, triggering ADH release. This hormone then acts on the collecting ducts of the nephron, enhancing water reabsorption and concentrating urine.
• Effect of ADH on Kidneys: By promoting water reabsorption, ADH helps maintain blood pressure, blood volume, and overall fluid balance, proving vital for survival in different environmental conditions.

The integration of the endocrine system and kidney function via ADH demonstrates how hormonal control is essential for adapting the body's needs.