Human Digestive and Urinary Systems Quiz

Endocrine System

• Works with the nervous system to coordinate and integrate body cell activity
• Influences metabolic activities via hormones transported in the blood

Hormone Signaling

• Autocrine signaling: Hormones affect the cells that secrete them
• Paracrine signaling: Hormones affect nearby cells but not the ones that secrete them
• Endocrine signaling: Hormones travel throughout the body affecting distant cells

Hormone Release

• Endocrine glands are stimulated to synthesize and release hormones in response to:
  • Humoral stimuli
  • Neural stimuli
  • Hormonal stimuli

Hormone Levels

• Blood hormone levels are controlled by negative feedback
  • Increased hormone effects on target organs inhibit further hormone release
• Nerve fibers stimulate hormone release (sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines)
• Hormones released in response to altered levels of ions or nutrients

Hormone Actions

• Hormone specificity: Only cells with specific receptors are affected
• Target cell activation depends on:
  • Blood levels of the hormone
  • Relative number of receptors on the target cell
  • Affinity of binding between receptor and hormone
• Up-regulation: Target cells form more receptors in response to low hormone levels
• Down-regulation: Target cells lose receptors in response to high hormone levels
• Mechanisms of hormone action: hormones alter target cell activity by changing membrane permeability and/or membrane potential, stimulating synthesis of enzymes, and activating or inhibiting enzymes, or causing mitosis

Classes of Hormones

• Amino acid-based hormones:
  • Water-soluble
  • Examples: epinephrine, melatonin, and insulin
• Steroid hormones:
  • Lipid-soluble
  • Synthesized from cholesterol
  • Examples: gonadal and adrenocortical hormones
• Specific actions of hormones: water-soluble hormones mostly affect plasma membrane receptors, while lipid-soluble hormones mostly affect intracellular receptors that directly activate genes

Hormone Characteristics

• Hormones circulate in blood as either free or bound to plasma proteins
• Hormone concentration reflects the rate of release and speed of inactivation/removal from the body
• Hormones can be removed from blood by degradation enzymes, kidneys, and liver

Half-life of hormones

• The time required for the concentration of hormone in the blood to decrease by half. It ranges I minute to I week.

Endocrine Glands (Pituitary)

• Connected to the hypothalamus
• Secretes several major hormones

Anterior Pituitary (Adenohypophysis)

• Composed of glandular tissue
• Consists of peptide hormones
• Tropic hormones regulate secretion of other hormones
• Releasing and inhibiting hormones

Anterior Pituitary Hormones

• Acts directly or indirectly
• Stimulates other endocrine organs to release hormones
• Examples: ACTH, FSH, LH, GH

ACTH

• Secreted by corticotropic cells
• Stimulates adrenal cortex to release corticosteroids

Gonadotropins (FSH & LH)

• Secreted by gonadotropic cells
• Regulate gamete production and gonadal hormone production
• Stimulate follicle development and egg release in females
• Stimulate testes in males

Thyroid Gland

• Major metabolic hormone:
• T4 (Thyroxine): major form circulating in blood (has 4 iodine atoms attached)
• T3 (triiodothyronine): more active in tissues (has 3 iodine atoms attached)

Calcitonin

• Produced by parafollicular cells
• Lowers blood calcium levels by inhibiting osteoclast activity

Parathyroid

• Regulates blood calcium by increasing calcium levels

Adrenal Glands

• Composed of adrenal cortex and adrenal medulla
• Adrenal cortex: synthesizes and secretes steroid hormones

Mineralocorticoids

• Regulates electrolyte concentration (primarily Na+ and K+) in ECF and blood volume
• Aldosterone is a potent mineralocorticoid
• Renin-angiotensin-aldosterone mechanism is the primary regulator of aldosterone secretion

Glucocorticoids

• Influences glucose metabolism and helps maintain blood pressure and blood composition
• Examples: Cortisol (major)

Adrenal Medulla

• Synthesizes epinephrine (80%) and norepinephrine (20%)

Pancreas

• Has exocrine and endocrine cells
• Acinar cells (exocrine) produce pancreatic juice for digestion, with islets containing endocrine cells
• Alpha cells secrete glucagon (hyperglycemic)
• Beta cells secrete insulin (hypoglycemic)

Digestive System

• Ingestion, mechanical breakdown, propulsion, digestion, absorption, and defecation
• Accessory digestive organs: teeth, tongue, gallbladder, liver, pancreas

Digestive System Processes

• Ingestion — Taking food into the mouth
• Mechanical breakdown — Chewing of food
• Propulsion — Movement of food through digestive tract
• Digestion — Chemical breakdown of food into smaller molecules
• Absorption — Movement of nutrients from the digestive tract into the blood
• Defecation — Removal of waste from the body

Digestive System Layers

• Mucosa (innermost layer)
• Submucosa (connective tissue)
• Muscularis (smooth muscles)
• Serosa (outermost layer)

Digestive Enzymes

• Salivary amylase, pepsin, trypsin, pancreatic lipase
• Intrinsic factors helps with vitamin B12 absorption

Gastric Glands

• Cephalic phase: prepares stomach for food
• Gastric phase : Food reaches stomach, stimulates gastric secretions
• Intestinal phase: Food enters small intestine, slows gastric secretions

Liver

• Produces bile, crucial for lipid digestion, and helps neutralize stomach acid
• Contains hepatocytes, producing bile
• Produces ~900 ml of bile per day

Gallbladder

• Stores and concentrates bile
• Bile duct releases bile into the small intestine

Pancreas

• Exocrine cells produce pancreatic juice which contains digestive enzymes
• Endocrine cells produce hormones like insulin and glucagon.

Small intestine

• Site of most digestion and absorption
• Duodenum, jejunum, and ileum
• Superior mesenteric artery provides blood supply

Regulation of Gastric Emptying

• Stomach empties in 4 hours, with carb-rich chyme emptying more quickly than fatty chyme
• Duodenum receptors and hormones regulate gastric secretion

Urinary system

• Kidneys filter blood, producing urine, maintaining homeostasis of electrolyte and water balance.
• Main processes: glomerular filtration, tubular reabsorption, tubular secretion
• Two main parts: renal corpuscle and renal tubule

Glomerular filtration

• Filtration of blood into the glomerular capsule by hydrostatic pressure through the filtration membrane.
• Glomerular filtration rate (GFR) is the volume of filtrate formed per minute in both kidneys (120-125 ml/min)

Regulation of GFR

• Intrinsic controls (autoregulation): Myogenic mechanism and tubuloglomerular feedback.
• Extrinsic controls (neural and hormonal): sympathetic nervous system, renin-angiotensin-aldosterone system, and atrial natriuretic peptide.

Tubular reabsorption and secretion

• Tubular reabsorption: Reabsorption of water, ions, and other substances from the filtrate back into the blood.
• Tubular secretion: Secretion of substances from the blood into the filtrate.

Test your knowledge on the human digestive and urinary systems with this comprehensive quiz. Explore questions on the alimentary canal, accessory digestive organs, insulin release, and the nephron's function, including absorption and secretion processes. Perfect for students studying human anatomy and physiology.