Practice Flashcards: Urinary, Digestive, and Reproductive Systems

A comprehensive set of vocabulary flashcards covering the renal filtration membrane, Juxtaglomerular Apparatus, acid-base homeostasis, digestive cell types and phases, and male and female reproductive anatomy and hormonal cycles.

Filtration membrane

The three-layered barrier through which fluid passes in the glomerulus, consisting of fenestrated endothelium, a basement membrane, and filtration slits.

Fenestrated endothelium

The layer of glomerular capillaries containing pores $70$ to $90\,\text{nm}$ in diameter, small enough to exclude blood cells but highly permeable.

Basement membrane

A proteoglycan gel with a negative charge that excludes molecules greater than $8\,\text{nm}$ and repels albumin; it maintains the filtrate at only $0.03\%$ protein compared to $7\%$ in plasma.

Filtration slits

Gaps of $30\,\text{nm}$ formed by podocyte cell extensions called pedicels that wrap around capillaries and provide a negatively charged obstacle for large anions.

Net filtration pressure (NFP)

The resulting outward pressure in the glomerulus, calculated as $10\,\text{mm Hg}<em>{\text{out}}$, derived from Blood Hydrostatic Pressure ($60\,\text{mm Hg}</em>{\text{out}}$), Colloid Osmotic Pressure ($-32\,\text{mm Hg}<em>{\text{in}}$), and Capsular Pressure ($-18\,\text{mm Hg}</em>{\text{in}}$).

Macula densa (MD) cells

Chemoreceptors in the juxtaglomerular apparatus that monitor the osmolarity and chemical composition of the filtrate.

Juxtaglomerular (JG) cells

Also known as granular cells, these are baroreceptors that measure blood pressure and stretch in the afferent arteriole.

Myogenic mechanism

The autoregulation process where smooth muscle contracts when stretched to prevent high arterial blood pressure from changing blood flow into the glomerulus.

Tubuloglomerular feedback

A mechanism where the macula densa senses high GFR (increased NaCl load) and secretes ATP, causing the afferent arteriole to constrict and return GFR to normal.

Renal fraction

The portion of the cardiac output that passes to the kidneys, equal to approximately $20\%$ or $1200\,\text{mL/min}$.

Glomerular filtration rate (GFR)

The rate of filtrate generation, averaging $125\,\text{mL/min}$ or approximately $180\,\text{L/day}$, with $99\%$ of the filtrate being reabsorbed.

Transport maximum ($T_{\text{max}}$)

The limit of solute reabsorption determined by the number of transport proteins; for glucose, any blood level above $220\,\text{mg/dL}$ results in glycosuria.

Countercurrent Multiplier

The process in the nephron loop where more salt is pumped into the ECF by the ascending limb, which then causes more water to leave the descending limb by osmosis.

Principal cells

The most numerous cells in the DCT and collecting duct, containing receptors for hormones like aldosterone, PTH, ADH, and ANP to regulate salt and water balance.

Intercalated cells

Cells in the DCT and collecting duct involved in acid-base balance by secreting $\text{H}^+$ into the tubule lumen and reabsorbing $\text{K}^+$.

Obligatory water reabsorption

The non-preventable movement of water that recovers $85\%$ of filtrate, primarily using aquaporin-1s in the PCT.

Facultative water reabsorption

The controlled reabsorption of the remaining $15\%$ of filtrate volume ($27\,\text{L/day}$) in the DCT and collecting system, regulated by ADH and aquaporin-2s.

Renal clearance ($C$)

The volume of blood plasma from which a particular waste is completely removed in one minute, calculated as $C = UV/P$.

Detrusor muscle

The three-layered smooth muscle of the urinary bladder muscularis.

Micturition

The act of urinating, partially controlled by an involuntary spinal reflex and voluntary control involving the pons and cerebrum.

Acidosis

A condition where the plasma pH is less than $7.35$.

Alkalosis

A condition where the plasma pH is greater than $7.45$.

Carbonic acid-bicarbonate buffer system

The most important buffer system in the ECF, which requires a functioning respiratory system and relies on the availability of bicarbonate ions.

Respiratory compensation

A change in respiratory rate to stabilize ECF pH; an increase in respiration decreases $\text{H}^+$ and raises pH, while slowing respiration increases $\text{H}^+$ and lowers pH.

Enteric nervous system

The local nervous network of the digestive tract composed of the submucosal plexus (controlling secretions/mucosa) and the myenteric plexus (controlling peristalsis).

Parietal cells

Stomach cells that secrete hydrochloric acid (HCl), the hunger hormone ghrelin, and intrinsic factor.

Chief cells

The most numerous stomach cells, responsible for secreting gastric lipase and the zymogen pepsinogen.

Zymogens

Digestive enzymes secreted as inactive proteins (proenzymes), such as pepsinogen or trypsinogen, which are activated by removing amino acids.

Intrinsic factor

A glycoprotein secreted by parietal cells that is essential for the absorption of Vitamin $\text{B}_{12}$ by the small intestine.

Cephalic phase

The initial phase of gastric control where the brain (vagus nerve) stimulates gastric secretion based on the sight, smell, or taste of food.

Bile

A yellow-green fluid produced by hepatocytes containing minerals, cholesterol, neutral fats, phospholipids, and bile acids/salts needed for fat emulsification.

Pancratic juice

An alkaline mixture of water, enzymes, zymogens, and sodium bicarbonate that buffers $\text{HCl}$ from the stomach.

Trypsin

An autocatalytic enzyme activated from trypsinogen by enteropeptidase; it further activates chymotrypsinogen and procarboxypeptidase.

Duodenum

The first $25\,\text{cm}$ of the small intestine where stomach acid is neutralized and chemical digestion is completed.

Peyer's patches

aggregated lymphoid nodules located in the ileum of the small intestine.

Gut microbiome

About $800$ species of bacteria in the large intestine that digest cellulose/pectin and help synthesize vitamins B and K.

Cremaster muscle

Skeletal muscle from the internal oblique that draws the testes closer to the body to regulate temperature.

Tunica albuginea

The fibrous capsule of the testes that partitions them into $250$ to $300$ lobules.

Sustentacular (Sertoli) cells

Support cells that promote sperm development, form the blood-testis barrier, and produce androgen-binding protein (ABP) and inhibin.

Interstitial (Leydig) cells

Cells found between seminiferous tubules that produce testosterone.

Acrosome

A cap on the head of the sperm containing enzymes used to penetrate the egg.

GnRH (Gonadotropin-Releasing Hormone)

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

Stratum functionalis

The outer part of the endometrium closest to the uterine cavity that is created and destroyed monthly during the menstrual cycle.

Oogenesis

The process of female gamete production; it begins before birth, pauses in prophase I until puberty, and results in one functional ovum and nonfunctional polar bodies.

Corpus luteum

An endocrine structure formed from granulosa cells after ovulation that produces progesterone and estrogen to maintain the stratum functionalis.