Functions and Anatomy of Digestive and Urinary Systems

Functions of the digestive system

Ingestion, digestion, absorption, compaction, defecation.

Alimentary canal organs

Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus.

Accessory digestive organs

Teeth, tongue, salivary glands, liver, gallbladder, pancreas.

Layers of the GI tract wall

Mucosa, submucosa, muscularis externa, serosa.

Mesenteries

Folds of peritoneum that support and anchor digestive organs.

Enzyme in saliva for starch digestion

Salivary amylase.

Phases of swallowing

Oral (voluntary), pharyngeal (involuntary), esophageal (involuntary).

Main stomach secretions

HCl, pepsinogen, gastric lipase, intrinsic factor, mucus.

Function of intrinsic factor

Enables absorption of vitamin B12 in the small intestine.

Regions of the small intestine

Duodenum, jejunum, ileum.

Primary function of the jejunum

Most digestion and nutrient absorption.

Organ that produces bile

Liver.

Function of the gallbladder

Stores and concentrates bile.

Contents of pancreatic juice

Digestive enzymes and bicarbonate.

Enzymes that digest carbohydrates

Amylase, maltase, sucrase, lactase.

Protein digestion

By pepsin, trypsin, chymotrypsin, and carboxypeptidase.

Lipid digestion

Emulsified by bile, digested by lipase.

Function of the large intestine

Absorbs water and electrolytes; compacts feces.

Vitamins absorbed without digestion

Water-soluble (B, C) and fat-soluble (A, D, E, K—require fat).

ATP

Adenosine triphosphate; produced from glucose via glycolysis, TCA cycle, and ETC.

Functions of the urinary system

Excrete wastes, regulate blood volume/pressure/osmolarity, acid-base balance, erythropoietin, detox, glucose production.

Major nitrogenous wastes

Urea, uric acid, creatinine.

Azotemia

Elevated BUN, may indicate renal insufficiency.

Systems contributing to excretion

Urinary, respiratory, digestive, integumentary.

Parts of a nephron

Renal corpuscle (glomerulus + capsule), PCT, loop, DCT, collecting duct.

Filtrate flow in the nephron

Capsule → PCT → loop → DCT → collecting duct → papillary duct → calyx → pelvis → ureter.

Stages of urine formation

Glomerular filtration, tubular reabsorption, tubular secretion, water conservation.

Hormone increasing water reabsorption

ADH (antidiuretic hormone).

Na+ and water reabsorption

Promotes Na+ and water reabsorption in DCT and collecting duct.

Average urine output

1-2 liters.

Polyuria

>2 L/day.

Oliguria

<500 mL/day.

Anuria

<100 mL/day.

Proteinuria

Protein or blood in urine—signs of kidney damage/infection.

Hematuria

Protein or blood in urine—signs of kidney damage/infection.

Urinary bladder

Structure that stores urine.

Muscles controlling urination

Detrusor, internal sphincter (involuntary), external sphincter (voluntary).

Thirst trigger

Increased blood osmolarity sensed by hypothalamic osmoreceptors.

Main ECF cation

Sodium (Na+); controls water balance and membrane potential.

Main ICF cation

Potassium (K+).

Buffer

System that resists changes in pH by binding or releasing H+.

Normal pH of blood

7.35-7.45.

Metabolic acidosis

Low pH due to excess acid or base loss (e.g., diabetes, diarrhea).

Primary sex organs

Gonads: testes in males, ovaries in females.

SRY gene

Initiates development of testes in XY individuals.

Male reproductive tract ducts

Males: mesonephric (Wolffian); Females: paramesonephric (Müllerian).

Cryptorchidism

Failure of testes to descend into the scrotum.

Cremaster muscle

Muscle that draws the testes closer to the body in cold temperatures.

Pampiniform plexus

Structure that cools arterial blood before it reaches the testes.

Spermatogenesis location

Occurs in seminiferous tubules of the testes.

Testosterone production cells

Interstitial (Leydig) cells.

Sertoli cells function

Nourish and protect developing sperm; form blood-testis barrier.

Accessory glands in male reproductive system

Seminal vesicles, prostate gland, bulbourethral glands.

Semen production percentage by seminal vesicles

~60%.

BPH

Benign prostatic hyperplasia—noncancerous prostate enlargement.

Puberty trigger hormone

GnRH (gonadotropin-releasing hormone).

Ovaries function

Produce oocytes (eggs) and hormones (estrogen, progesterone).

Layers of the uterine wall

Perimetrium, myometrium, endometrium.

Endometrium layer shed during menstruation

Stratum functionalis.

Hormones produced by corpus luteum

Estrogen, progesterone, and inhibin.

LH surge trigger event

Ovulation.

Onset of puberty in girls

Thelarche (breast development).

Menopause

Cessation of menstrual cycles, usually around age 45-55.

FSH purpose in females

Stimulates follicle development in the ovaries.

Phases of the menstrual cycle

Menstrual, proliferative, secretory, premenstrual.