Digestive & Reproductive Systems — Key Vocabulary (Weeks 6–7)

A set of vocabulary-style flashcards covering major terms from weeks 6–7 notes on the Digestive and Reproductive systems.

Motility

Movement of food along the GI tract via peristalsis, segmentation, and migrating motor complex (MMC).

Secretion

Release of enzymes, fluids, bile, and mucus to aid digestion and lubrication.

Digestion

Mechanical (chewing, mixing) and chemical (enzymes, acids) breakdown of food.

Absorption

Transport of nutrients into blood or lymphatic system.

Autodigestion

Risk of digestive enzymes harming the body's own tissues; prevented by mucus and inactive enzyme forms.

Mass balance

Equilibrium between secretion and absorption to maintain water/electrolyte balance.

Defense (GI tract)

Protection against pathogens in ingested food.

Mucus layer

Protects the epithelium from mechanical and chemical injury.

Bicarbonate secretion

Neutralizes stomach acid to protect the mucosa.

Tight junctions

Connections between epithelial cells that prevent leakage of contents.

Peyer’s patches

Lymphoid tissue in the gut involved in immune surveillance.

GALT (gut-associated lymphoid tissue)

Immune tissue in the gastrointestinal tract, including Peyer’s patches.

Peyer's patches

Lymphoid nodules in the small intestine that monitor intestinal bacteria.

Enteric Nervous System (ENS)

Neural network in the GI tract that can function autonomously to regulate motility and secretion.

Central Nervous System (CNS)

Brain and spinal cord; integrates with GI via extrinsic nerves and hormones.

ACh (GI)

Acetylcholine; principal parasympathetic/ENS neurotransmitter affecting GI activity.

NO (GI)

Nitric oxide; neurotransmitter involved in GI motility and relaxation.

Serotonin (GI)

Neurotransmitter involved in GI signaling and motility.

Peristalsis

Wave-like, propulsive muscular contractions moving contents forward.

Segmentation

Rhythmic, non-propulsive contractions that mix chyme for absorption.

Migrating Motor Complex (MMC)

Housekeeping motility that clears residual food/bacteria between meals.

Tonic contractions

Long-lasting contractions seen in sphincters and the stomach.

Phasic contractions

Short, rhythmic contractions in the esophagus and small intestine.

ENS vs CNS

ENS is intrinsic to the GI tract and can operate independently; CNS involves brain/spinal input.

Saliva

Water, mucus, and amylase; lubricates, begins carbohydrate digestion, and has antibacterial properties.

Gastric juice

HCl, pepsinogen, mucus, intrinsic factor; aids digestion and protection in the stomach.

Pancreatic juice

Digestive enzymes plus bicarbonate released into the small intestine.

Bile

Emulsifies fats to aid digestion and absorption.

Liver

Produces bile; stores vitamins/minerals; detoxifies substances.

Gallbladder

Stores and concentrates bile for release into the duodenum.

Intestinal glands

Glands in the small intestine that secrete intestinal juice and mucus.

Intestinal juice

Secretions rich in enzymes and mucus from the intestinal glands.

Brush border enzymes

Enzymes on the microvilli of enterocytes that finish digestion (e.g., disaccharidases).

Chylomicrons

Lipoprotein particles that transport absorbed lipids via the lymphatic system.

Micelles

Bile salt–bile acid aggregates that aid lipid absorption.

Gastrin

Gastric hormone that stimulates acid secretion and motility.

HCl

Hydrochloric acid in the stomach; denatures proteins and activates pepsin.

Pepsinogen/Pepsin

Inactive pepsinogen converted to pepsin by acid; digests proteins.

Intrinsic factor

Glycoprotein essential for vitamin B12 absorption in the ileum.

Parietal cells

Stomach cells that secrete HCl and intrinsic factor.

Chief cells

Stomach cells that secrete pepsinogen and gastric lipase.

Mucous cells

Stomach cells that secrete protective mucus and bicarbonate.

G cells

Gastrin-secreting cells that regulate acid secretion and motility.

Duodenum

First section of the small intestine where chyme mixes with bile and pancreatic secretions.

Jejunum

Middle section of the small intestine where most absorption occurs.

Ileum

Last section of the small intestine where bile acids and B12 are absorbed.

Cecum

Beginning part of the large intestine; fermentation and absorption.

Large intestine

Absorbs water/electrolytes and forms feces; houses gut microbiota.

Ascending/Transverse/Descending/Sigmoid colon

Sections of the large intestine involved in water absorption and feces formation.

Rectum

Stores and expels feces; terminal portion of the GI tract.

Anus

Opening for defecation; controlled by internal and external sphincters.

Secretory IgA

Antibody that prevents pathogen binding in the GI tract.

Microbiota

Resident gut bacteria that compete with pathogens and support gut health.

Hepatic Portal System

Blood pathway from gut to liver for nutrient processing and detoxification.

Hepatic portal vein

Carry nutrient-rich blood from GI tract to liver.

Liver sinusoids

Capillary vessels through which blood from the portal system flows in the liver.

Hepatic veins

Drain processed blood from the liver to the inferior vena cava.

Inferior vena cava

Main systemic vein returning blood to the heart.

Pancreas (exocrine)

Secretes digestive enzymes and bicarbonate into the duodenum.

Pancreas (endocrine)

Islets of Langerhans secrete insulin, glucagon, and somatostatin.

Islets of Langerhans

Endocrine cell clusters producing hormones regulating blood glucose.

Insulin

Hormone lowering blood glucose by promoting uptake into cells.

Glucagon

Hormone raising blood glucose by stimulating glucose release.

Somatostatin

Hormone inhibiting release of several other hormones and digestive processes.

Bile salts

Bile components that emulsify fats, aiding digestion and absorption.

Bilirubin

Pigment in bile from heme breakdown; contributes to bile color.

Cholesterol & Phospholipids (bile components)

Bile constituents aiding fat digestion and lipid absorption.

Flow of bile

Liver → canaliculi → ducts → hepatic ducts → cystic duct (to gallbladder) or common bile duct (to duodenum).

Digestion of carbohydrates

Salivary/pancreatic amylase breaks starches to disaccharides; brush border enzymes yield monosaccharides.

Digestion of lipids

Bile salts emulsify fats; pancreatic lipase; absorbed as micelles and transported as chylomicrons.

Digestion of proteins

Pepsin in the stomach; pancreatic proteases in the small intestine; peptides to amino acids.

Nucleic acid digestion

Nucleases break nucleic acids into nucleotides.

Immune functions of GI tract

Mucus/acid barriers, GALT, secretory IgA, and protective microbiota.

Mast or accessory reproductive glands

Seminal vesicles (alkaline, fructose-rich fluid), prostate (milky fluid with activating enzymes), bulbourethral glands (mucus for lubrication and pH neutralization).

Spermatogenesis

Process of sperm production in the seminiferous tubules.

Spermatogonia

Diploid stem cells that divide to produce sperm cells.

Primary spermatocytes

Diploid cells undergoing meiosis I.

Secondary spermatocytes

Haploid cells undergoing meiosis II.

Spermatids

Immature haploid sperm cells that mature via spermiogenesis.

Spermiogenesis

Maturation of spermatids into functional spermatozoa.

Duration of spermatogenesis

Approximately 64–72 days for a complete cycle.

Mons pubis

Fatty pad over the pubic bone in females.

Labia majora/minora

Protective folds surrounding the vaginal opening.

Clitoris

Erectile tissue involved in female sexual stimulation.

Vestibular glands (Bartholin’s glands)

Lubricating glands located near the vaginal opening.

Ovaries

Gonads that produce ova and sex hormones (estrogen, progesterone).

Fallopian tubes (oviducts)

Transport ova; site of fertilization.

Uterus

Organs housing and nourishing the embryo/fetus; three layers: perimetrium, myometrium, endometrium.

Cervix

Narrow opening between uterus and vagina; secretes mucus.

Vagina

Birth canal and site of copulation; passage for menstrual flow.

Mammary glands

Breasts that produce milk for infant nourishment.

Oogenesis

Egg formation in ovaries.

Oogonia

Stem cells in ovaries that divide to form primary oocytes.

Primary oocytes

Oocytes arrested in prophase I until puberty.

Secondary oocyte

Oocyte that completes meiosis I and proceeds to meiosis II if fertilized.

Polar bodies (egg development)

Small, nonfunctional cells produced during meiosis in oogenesis.

Ovum

Mature female gamete produced after meiosis II (if fertilization occurs).

Ovarian cycle phases

Follicular phase, ovulation, luteal phase describing ovarian changes across ~28 days.

Follicular phase

FSH-stimulated follicle growth; estrogen secretion.

Ovulation

LH surge releases secondary oocyte from ovary.