Excretory Products and Their Elimination

Comprehensive vocabulary flashcards covering the biological processes of excretion, human renal anatomy, urine formation, and related disorders.

Ammonotelism

The process of excreting ammonia, which is the most toxic form of nitrogenous waste and requires large amounts of water for its removal.

Ureotelic animals

Animals such as mammals, many terrestrial amphibians, and marine fishes that mainly excrete urea.

Uricotelic animals

Animals like reptiles, birds, land snails, and insects that excrete nitrogenous wastes as uric acid in the form of a pellet or paste with minimum water loss.

Protonephridia (Flame cells)

Excretory structures in Platyhelminthes (e.g., Planaria), rotifers, some annelids, and the cephalochordate – Amphioxus, primarily concerned with osmoregulation.

Nephridia

Tubular excretory structures of earthworms and other annelids that help remove nitrogenous wastes and maintain fluid and ionic balance.

Malpighian tubules

Excretory structures of most insects including cockroaches that assist in the removal of nitrogenous wastes and osmoregulation.

Antennal glands (Green glands)

Excretory structures that perform the excretory function in crustaceans like prawns.

Hilum

A notch towards the centre of the inner concave surface of the kidney through which the ureter, blood vessels, and nerves enter.

Renal pelvis

A broad funnel-shaped space inner to the hilum with projections called calyces.

Columns of Bertini

Extensions of the renal cortex that project between the medullary pyramids as renal columns.

Nephron

The functional unit of the kidney, with nearly one million present in each kidney, consisting of a glomerulus and a renal tubule.

Glomerulus

A tuft of capillaries formed by the afferent arteriole, which is a fine branch of the renal artery.

Malpighian body (Renal corpuscle)

The complex consisting of the glomerulus along with the double-walled cup-like Bowman’s capsule.

Proximal Convoluted Tubule (PCT)

A highly coiled network of the renal tubule lined by simple cuboidal brush border epithelium, where $70-80$ per cent of electrolytes and water are reabsorbed.

Henle’s loop

A hairpin-shaped part of the renal tubule with descending and ascending limbs that plays a significant role in maintaining high osmolarity of medullary interstitial fluid.

Cortical nephrons

Nephrons in which the loop of Henle is too short and extends only very little into the medulla.

Juxta medullary nephrons

Nephrons possessing a very long loop of Henle that runs deep into the medulla.

Vasa recta

A $U$-shaped minute vessel of the peritubular capillary network that runs parallel to the Henle’s loop; it is absent or highly reduced in cortical nephrons.

Glomerular Filtration Rate (GFR)

The amount of filtrate formed by the kidneys per minute, which is approximately $125\,ml/minute$ (or $180\,litres$ per day) in a healthy individual.

Juxta glomerular apparatus (JGA)

A special sensitive region formed by cellular modifications in the distal convoluted tubule and the afferent arteriole at their contact location, regulating GFR.

Ultra filtration

The process by which blood is filtered so finely through three layers (endothelium, basement membrane, and podocytes) that almost all plasma constituents except proteins pass into the Bowman’s capsule.

Podocytes

Epithelial cells of Bowman’s capsule arranged intricately to leave minute spaces called filtration slits or slit pores.

Reabsorption

The process by which nearly $99$ per cent of the filtrate is taken back by the renal tubules, either through active or passive mechanisms.

Tubular secretion

The step in urine formation where tubular cells secrete substances like $H^+$, $K^+$, and ammonia into the filtrate to maintain ionic and acid-base balance.

Counter current mechanism

The process facilitated by the arrangement of Henle’s loop and vasa recta that maintains a concentration gradient from $300\,mOsmolL^{-1}$ to $1200\,mOsmolL^{-1}$ in the medullary interstitium.

Micturition

The process of the release of urine initiated by a voluntary signal from the CNS, resulting in the contraction of smooth muscles of the bladder and relaxation of the urethral sphincter.

Glycosuria

The presence of glucose in urine, which is often indicative of diabetes mellitus.

Ketonuria

The presence of ketone bodies in urine, which is often indicative of diabetes mellitus.

Uremia

A condition where urea accumulates in the blood due to malfunctioning of the kidneys, which can lead to kidney failure.

Hemodialysis

A process for removing urea from the blood of uremic patients using an artificial kidney unit containing a coiled cellophane tube.

Renal calculi

Stone or insoluble mass of crystallised salts, such as oxalates, formed within the kidney.

Glomerulonephritis

Inflammation of the glomeruli of the kidney.