Kidney and Urinary System

What is the primary function of the kidneys?

To filter the blood and produce urine

What is the renal capsule?

A fibrous coating surrounding the kidney

Where is the cortex located?

The outer layer of the kidney

Where is the medulla located?

The inner layer of the kidney

What are renal pyramids?

Structures in the medulla that appear slightly darker than the cortex

What do renal columns do?

They carry blood vessels to the cortex and separate the renal pyramids

What is the function of collecting ducts?

They collect urine and carry it through the renal pyramids and papilla into the minor calyces

What is the order of urine flow through the kidney?

Collecting ducts → renal papilla → minor calyx → major calyx → renal pelvis → ureter → bladder

What is the renal pelvis?

A funnel-shaped structure that collects urine before it enters the ureter

What does the renal artery do?

It brings blood to the kidney

What does the renal vein do?

It carries blood away from the kidney

Where is the nephron located?

Part of the nephron is in the cortex and part is in the medulla

What is the glomerulus?

A ball of capillaries that filters blood

What is the afferent arteriole?

It brings blood into the glomerulus for filtration

What is the efferent arteriole?

It carries blood away from the glomerulus

What is the order of the arterioles around the glomerulus?

Afferent → glomerulus → efferent

What is an easy way to remember afferent vs efferent?

"A before E" — afferent enters, efferent exits

What are the main parts of the loop of Henle?

• Thick descending limb & Thin descending limb

• Thin ascending limb & Thick ascending limb

What is the function of the collecting duct?

It helps regulate body fluid volume, acidity and salt reabsorption

What are peritubular capillaries?

Small blood vessels surrounding the renal tubules that allow reabsorption of essential substances and help regulate water balance.

What is the function of the vasa recta?

It supplies blood to the loop of Henle

What is Bowman’s capsule?

A capsule surrounding the glomerulus that collects the filtrate produced by filtration

What type of epithelium forms the outer layer of Bowman’s capsule?

Parietal epithelium

What is Bowman’s space?

The space where filtrate collects before entering the proximal tubule

What is glomerular filtration?

The process where water and small molecules are filtered from the blood into Bowman’s capsule

What is glomerular filtration rate (GFR)?

The rate at which blood is filtered through the glomeruli

Why does filtration occur in the glomerulus?

High blood pressure forces water and small molecules through the filtration barrier

What remains in the blood during glomerular filtration?

Blood cells and large plasma proteins

What lines the afferent and efferent arterioles?

Endothelial cells

Why do proximal tubule epithelial cells have a brush border?

To increase surface area for reabsorption

Where is the distal convoluted tubule located?

It is located near the afferent and efferent arterioles and is involved in regulating electrolyte balance

What is a podocyte?

A specialised cell forming the visceral epithelium of Bowman’s capsule that helps form the filtration barrier

What is the juxtaglomerular apparatus?

A specialised structure that helps regulate blood pressure and filtration in the kidney

What do granular cells of the juxtaglomerular apparatus release?

Renin

What do macula densa cells detect?

Sodium chloride (NaCl) concentration in the tubular fluid

What is the role of extraglomerular mesangial cells?

They help support and regulate the juxtaglomerular apparatus

What are the main functions of the kidneys?

Excretory, regulatory, metabolic and endocrine functions

What is the excretory function of the kidneys?

Producing urine to remove waste products

What is the regulatory function of the kidneys?

Maintaining water, electrolyte and acid-base balance

What is the metabolic function of the kidneys?

They metabolise vitamin D and help control blood calcium levels and bone formation

What is the endocrine function of the kidneys?

They produce hormones such as renin and erythropoietin

What happens during filtration?

Water and small molecules pass through the filtration barrier into Bowman’s space, while blood cells and large plasma proteins remain in the blood

What is selective reabsorption?

The movement of useful substances from the renal tubules back into the blood

Where does selective reabsorption mainly occur?

In the renal tubules

How does active transport help with reabsorption?

It actively moves substances across the epithelial cells of the renal tubules

What is the renal threshold?

The level above which a substance can no longer be completely reabsorbed and begins to appear in urine

What can happen when the renal threshold for glucose is exceeded?

Glucose appears in the urine

Which hormones regulate calcium and phosphate reabsorption?

Parathyroid hormone (PTH) and calcitonin

What does antidiuretic hormone (ADH) do?

It increases water reabsorption, reducing urine volume.

When is ADH particularly important?

During dehydration

What does aldosterone do?

It increases sodium reabsorption and potassium excretion

What is tubular secretion?

The active movement of waste products, excess ions and certain drugs from the blood into the renal tubule for excretion

Where does the body gain water from?

Food and drink

How does the body lose water?

Through urine, faeces, perspiration and expired air

Why is water balance important?

It maintains homeostasis and normal cell volume

What hormone regulates water reabsorption?

Antidiuretic hormone (ADH)

What is a diuretic?

A drug or substance that increases urine production

What is an antidiuretic?

A substance that reduces urine production

Where is ADH produced?

In the hypothalamus

Where is ADH stored and released?

It is stored and released from the posterior pituitary gland

How does ADH reach the posterior pituitary?

It travels down the pituitary stalk from the hypothalamus

What are osmoreceptors?

Receptors in the hypothalamus that detect changes in blood osmolarity

What happens when blood osmolarity increases?

Osmoreceptors detect the change and increase ADH release, causing more water to be reabsorbed

How does the hypothalamus help regulate water balance?

Osmoreceptors in the hypothalamus detect changes in blood osmolarity and regulate ADH release

Where do sodium and potassium come from?

They are mainly obtained from food

How is excess sodium and potassium removed?

They are excreted in urine

Which hormone regulates sodium reabsorption?

Aldosterone

Which hormones coordinate calcium balance?

Parathyroid hormone (PTH) and calcitonin

What does parathyroid hormone do in the kidney?

It increases calcium reabsorption by the kidney tubules

What does calcitonin do in the kidney?

It decreases calcium reabsorption by the kidney tubules