Kidney Anatomy and Nephron Function

Vocabulary terms and definitions related to kidney anatomy, nephron structure, urine formation processes, and renal physiology based on the lecture transcript.

Renal capsule

The hard, fibrous outer covering of the kidney made of dense irregular connective tissue that protects against infection and friction.

Cortex

The light-colored, granular superficial region of the kidney that contains most of the blood vessels.

Medulla

The middle layer of the kidney containing triangularly shaped structures called pyramids.

Hilum

The midline of the kidney where the renal artery, renal vein, and renal pelvis are located.

Renal pelvis

The flat, funnel-shaped tube that is the expanded upper end of the ureter.

Renal sinus

The space within the middle hilum of the kidney containing the renal pelvis, renal artery, and renal vein.

Nephron

The tiny functional unit of the kidney responsible for filtering blood to create urine.

Renal corpuscle

The part of the nephron composed of the glomerulus and the Bowman's capsule (glomerular capsule).

Glomerulus

A big ball or nod of capillaries inside a nephron where blood filtration occurs.

Afferent arteriole

The blood vessel that delivers blood into the glomerulus.

Efferent arteriole

The blood vessel that blood flows through to exit the glomerulus if it is not filtered.

Podocytes

Specialized cells with little slits in the glomerulus that allow substances to move into the glomerular capsule if they meet size and ionic criteria.

Proximal convoluted tubule (PCT)

The nephron structure that reabsorbs $70\%$ of the fluid filtered in the glomerulus using an epithelial layer with a brush border of microvilli.

Loop of Henle

Also known as the loop of nephron, it consists of a descending limb and an ascending limb where water and salt are moved.

Distal convoluted tubule (DCT)

The segment of the nephron made of epithelial cells with mitochondria that uses ATP for tubular secretion of substances.

Collecting duct

A tube that collects urine from the distal convoluted tubules of several nephrons and opens at the apex of the medullary pyramid.

Cortical nephrons

Type of nephrons (forming $80\%$ of the total) with short loops of Henle that extend only a short distance into the medulla.

Juxtamedullary nephrons

Type of nephrons with long loops of Henle extending deep into the medulla that assist in acid-base balance.

Vasa recta

A group of blood vessels associated with juxtamedullary nephrons where blood flows slower to allow for increased filtration.

Glomerular filtration

The first step in urine formation where substances move from the glomerular capillaries into the glomerular capsule.

Tubular reabsorption

The process where substances, such as glucose, move from the renal tubules back into the peritubular capillaries.

Tubular secretion

The process requiring energy (ATP) to move substances from the plasma of the peritubular capillaries into the fluid of the renal tubules.

Glomerular Filtration Rate (GFR)

The amount of filtrate produced in the kidneys every minute, averaging about $125\,ml/min$ or $180\,liters$ per day.

Net filtration pressure

The favoring force for filtration (capillary blood pressure) minus the opposing forces (capsular hydrostatic pressure and colloid osmotic pressure).

Renin

An enzyme Produced by the kidneys that facilitates the production of angiotensin I from angiotensinogen.

ACE (Angiotensin Converting Enzyme)

An enzyme produced by the lungs that converts angiotensin I to angiotensin II.

Aldosterone

A hormone produced under the influence of angiotensin II that affects the concentration of sodium in urine.

Antidiuretic hormone (ADH)

A hormone from the posterior pituitary that increases water reabsorption in the distal convoluted tubules and collecting ducts.

Symport

A cotransport mechanism where a moiety like glucose moves in the same direction as sodium.

Antiport

A counter-transporter mechanism where a substance like potassium or hydrogen moves in the opposite direction of sodium.

Pinocytosis

A form of endocytosis or "cell drinking" used to intake fluids or large substances such as proteins in the kidney.

Parathyroid hormone (PTH)

A hormone that increases calcium reabsorption specifically in the thick ascending loop of Henle and distal tubules.