Urinary System (Part 1) Lecture Flashcards

Comprehensive vocabulary flashcards covering the anatomy, physiology, and fluid regulation mechanics of the urinary system based on Week 18 lecture notes.

Plasma

The intravascular fluid component of the ECF which is made up of $90\%$ water.

Fluid Balance (Body Water)

The condition where the body consists of $75\%$ water, noting that more adipose tissue results in less water.

Input = Output

The principle of fluid balance stating that the amount of water coming into the body (drinking, food, metabolism) must equal the amount leaving (skin, lungs, intestine, kidneys).

Urea

A nitrogenous waste product filtered from the blood (plasma) by the urinary system.

Erythropoietin

A substance manufactured by the urinary system to stimulate Red Blood Cell (RBC) production.

Kidney (Gross Structure)

A highly vascularised, lima bean shaped organ approximately $11\text{cm} \times 7\text{cm} \times 3\text{cm}$ in size.

Kidney Location

Positioned on either side of the vertebral column from the twelfth thoracic vertebrae ($T12$) to just above the third lumbar vertebrae ($L3$).

Hilum

A concave notch on the medial surface of the kidney through which renal blood vessels and other structures enter and exit.

Renal Cortex

The outer region of the kidney.

Renal Medulla

The inner region of the kidney.

Papilla

The base of the renal pyramid which contains multiple openings that release urine.

Renal Artery

A large branch of the abdominal aorta that brings blood to the kidney, eventually dividing into segmental, lobar, interlobar, and arcuate arteries.

Ureters

Tubes approximately $28\text{cm} - 32\text{cm}$ in length that take urine from the kidneys to the bladder via peristalsis.

Urinary Bladder

A muscular, collapsible bag located behind the pubic symphysis that serves as a reservoir for urine.

Detrusor Muscle

The smooth muscle tissue that composes the bladder wall.

Urethra

A small tube lined with mucous membrane that connects the bladder to the urinary meatus.

Nephron

The functional unit of the kidney, resembling a tiny funnel with a winding stem about $3\text{cm}$ long.

Renal Corpuscle

A region of the nephron consisting of the glomerulus and the Bowman capsule.

Glomerulus

A network of capillaries with porous endothelium necessary for the filtration of blood.

Bowman Capsule

The cup-shaped mouth of the nephron where fluids, waste, and electrolytes enter to become filtrate.

Proximal Convoluted Tubule (PCT)

The part of the renal tubule nearest to the Bowman capsule, featuring thousands of microvilli that form brush borders.

Loop of Henle

A segment of the renal tubule whose length is critical for producing highly concentrated or very diluted urine.

Distal Convoluted Tubule (DCT)

The portion of the renal tubule that conducts filtrate out of the nephron and into the collecting duct.

Juxtoglomerular Apparatus

A structure located where the afferent arteriole brushes past the distal tubule; it secretes renin when blood pressure drops.

Micturition

The process of urination or voiding, originating with the involuntary contraction of the detrusor muscle.

Internal Sphincter

A muscle that relaxes via a parasympathetic reflex when the bladder fills, allowing urine into the urethra.

Levator Ani

The skeletal muscle of the pelvic floor that acts as the external urethral sphincter for voluntary control of urination.

Distended Sensation Threshold

An average of $250\text{mls}$ of urine in the bladder causes the urge to void.