Quiz 6

Electrolytes

Ions in body fluids (e.g., Na⁺, K⁺, Cl⁻) that help regulate nerve and muscle function, hydration, and pH balance.

Obligatory exchanges

Unavoidable exchanges of water and solutes with the environment due to processes like respiration and excretion.

Nitrogenous wastes

Toxic byproducts of protein and nucleic acid metabolism, primarily including ammonia, urea, and uric acid.

Ammonia

A toxic nitrogenous waste excreted mainly by aquatic animals; requires large amounts of water for dilution.

Urea

A less toxic nitrogenous waste excreted by mammals and amphibians, produced in the liver via the urea cycle.

Uric Acid

A nitrogenous waste excreted by birds, insects, and reptiles; insoluble and excreted as a paste to conserve water.

Protonephridia

Excretory structures in flatworms consisting of flame cells and tubules; function in osmoregulation.

Metanephridia

Excretory organs in annelids that collect coelomic fluid and excrete waste via a tubule system.

Kidney

A vertebrate organ that filters blood, removes waste, and maintains water and electrolyte balance.

Ureter

A duct that transports urine from the kidney to the urinary bladder.

Urinary bladder

A muscular sac that stores urine before excretion.

Urethra

A tube that carries urine from the bladder to the exterior of the body.

Renal cortex

The outer layer of the kidney where filtration of blood begins.

Renal medulla

The inner part of the kidney, containing structures like the loops of Henle and collecting ducts.

Renal pelvis

A funnel-shaped cavity that collects urine from the kidney and channels it into the ureter.

Nephron

The functional unit of the kidney responsible for filtration, reabsorption, and secretion.

Proximal convoluted tubule

The first segment of the nephron where most reabsorption of water, ions, and nutrients occurs.

Loop of Henle

A U-shaped segment that creates a concentration gradient in the medulla to concentrate urine.

Distal convoluted tubule

A segment involved in selective reabsorption and secretion, regulated by hormones.

Peritubular capillaries

Capillaries surrounding the nephron tubules that reabsorb substances from filtrate.

Vasa recta

Capillaries surrounding the loop of Henle; help maintain the medullary concentration gradient.

Collecting duct

A channel that receives urine from nephrons and transports it to the renal pelvis.

Glomerulus

A tuft of capillaries where blood filtration begins in the nephron.

Bowman's capsule

A cup-like sac that encloses the glomerulus and collects the filtrate.

Podocytes

Specialized cells in Bowman's capsule that wrap around capillaries and aid in filtration.

Filtration slits

Gaps between podocyte processes through which filtrate passes.

Fenestrations

Pores in glomerular capillaries that allow the passage of small molecules but block cells and proteins.

Filtration

The process by which blood pressure forces fluid and solutes out of the glomerulus into Bowman's capsule.

Reabsorption

The movement of substances from the filtrate back into the blood.

Secretion

The active transport of additional waste substances from blood into the nephron.

Budding

Asexual reproduction in which a new organism develops from an outgrowth of a parent.

Fragmentation

Asexual reproduction in which an organism breaks into parts, each capable of growing into a new individual.

Parthenogenesis

A form of asexual reproduction where an embryo develops without fertilization.

Dioecious

Species with distinct male and female individuals.

Monoecious

Organisms that possess both male and female reproductive organs.

Synchronous hermaphroditism

Having both reproductive systems active at the same time.

Sequential hermaphroditism

An individual changes sex during its lifetime.

Penis

The external male reproductive organ involved in the delivery of sperm.

Scrotum

A pouch of skin containing the testes, regulating temperature for sperm production.

Testes

Male gonads that produce sperm and testosterone.

Seminiferous tubules

Tubes within the testes where sperm production occurs.

Epididymis

A long, coiled tube where sperm mature and are stored.

Vas deferens

A duct that transports mature sperm from the epididymis to the ejaculatory duct.

Spermatogonia

Diploid stem cells in the testes that give rise to sperm.

Primary spermatocytes

Cells derived from spermatogonia that undergo meiosis I.

Secondary spermatocytes

Haploid cells that result from meiosis I and proceed to meiosis II.

Spermatids

Immature haploid sperm cells formed from meiosis II.

Sertoli cells

Cells in the seminiferous tubules that support and nourish developing sperm.

Leydig cells

Cells located between seminiferous tubules that secrete testosterone.

Ejaculatory duct

A duct formed by the union of the vas deferens and the seminal vesicle duct; conveys sperm to the urethra.

Prostate gland

Produces a fluid that nourishes and protects sperm.

Seminal vesicle

Secretes a fluid rich in sugars to fuel sperm and substances to help sperm motility.

Bulbourethral gland

Produces pre-ejaculate fluid that lubricates and neutralizes acidic urine residues.

Gonadotropin releasing hormone (GnRH)

A hormone from the hypothalamus that stimulates the pituitary to release FSH and LH.

Follicle stimulating hormone (FSH)

Promotes spermatogenesis by stimulating Sertoli cells in males.

Luteinizing hormone (LH)

Stimulates Leydig cells to produce testosterone.

Testosterone

The primary male sex hormone, responsible for the development of male reproductive tissues and secondary sex characteristics.