Chapter 26, 27, & 28

Functions of Digestive System

1. Ingestion

2. Motility - smooth muscle

   1. peristalsis: propelling food along GI tract

   2. mixing

3. Secretion

   1. mucous: HCO₃^- protects against acidity

   2. enzymes, HCl, bile, hormones

4. Digestion

   1. breaking large molecules into smaller fragments

      • mechanical and chemical

5. Absorption

   1. take digested molecules out of GI tract and into blood

6. Elimination

Enteric Nervous System what is/how work?

• standalone system (no brain)

• sensory: (chemoreceptors and mechanoreceptors) - stretch

• integrator (neural plexi)

• motor output: smooth muscle, blood flow, secretory
  

Autonomic Nervous System - use for digestive system

• SNS: inhibitory

• PSNS: stimulatory

Oral Cavity - parts of digestive system

• Teeth: root attaches to bone, crown is visible, enamel covers crown

  • Used for Mastication: chewing (mechanical digestion)

• tongue: manipulate/mix (with saliva)

• salivary glands: secrete saliva → moisten/lubricate food, antibacterial, chemical digestion

Parts of Pharynx involved with digestion

Oropharynx and Laryngopharynx

General Structures of digestive system

1. Peritoneum (visceral/parietal)

   • serous: fluid that lubricates

   • covers internal organs

2. Mesenteries

   • folds of peritoneum that supports organs

Layers of GI space (inner to outer)

• Lumen

• mucosa:

  • absorption, simple epithelium

  • protection, stratified epithelium

• submucosa: blood vessels, nerves, lymphatics

• muscularis:

  • smooth muscle (circular and longitudinal)

  • sphincters (gates that regulate passage)

• adventitial/serosal: connective tissue

Esophagus Features

• Skeletal muscle in upper region

  • rest is smooth muscle

• peristalsis (propelling food further along GI tract)

• lower esophageal sphincter

  • (prevents backflow from stomach)

• no digestion/absorption

Stomach Features

• Little Absorption

• Pyloric Sphincter

  • prevents backflow from duodenum to stomach

• Gastric Folds: allows stomach to stretch

• Gastric Pits: lined with secretory cells

  • HCl, mucous HCO₃^-, enzymes

Small Intestine Features

3 Regions:

• Duodenum - attaches to stomach

• Jejunum - largest (middle)

• Ileum - connects to large intestine

Primary spot for Digestion & Absorption

Small Intestine Structural Adaptations

• Circular Folds — increase Surface Area

• Villi — more surface area “finger like” extensions

  • microvilli — even more surface area “hair like”

• cells secrete enzymes, hormones, and mucous

Renal System Function

1. urine formation, storage, and excretion

2. waste removal

3. regulation

   • blood volume, ion concentrations, acid-base balance, RBC formation (EPO)

Renal System Components

• Kidneys

• Ureters

• Bladder

• Urethra

Hilum of Kidney

entry & exit of blood vessels, nerves (SNS), and ureters

Layers of Kidney

1. Cortex: outer region

   • renal corpuscle, PCT + DCT

2. Medulla: deep inner region

   • nephron loop & collecting ducts

   • Pyramids (nephrons)

3. Renal columns blood vessels & nerves

Calyces (minor + major) (of Kidney)

inner region that originally collects urine

Renal Pelvis (of Kidney)

Big open area that collects urine

Flow of the kidney

filtration in nephron → collecting duct → minor + major calyces

renal pelvis → ureter → bladder → urethra

Vasculature of Kidney

Renal Artery → Afferent Arteriole → glomerular capillaries

(filtration occurs in glomerular capillaries)

Efferent Arterial → vasa recta or peritubular capillaries → veins

Vasculature and Nephron Model

Nephron Function

1. Filtration - removal of H₂O & contents from blood

   • Glomerulus

2. Reabsorption - return of filtered things back into blood

   • vasa recta & peritubular capillaries

3. Secretion - from blood to tubular fluid

4. Excretion - filter → reabsorb

Renal Corpuscle - part of filtration

Glomerulus

• filtration, fenestrated (porous) walls

• increased filtration - GFR (glomerular filtration rate)

Glomerular Capsule

• start of nephron

Proximal Tubule (PCT) - part of filtration

does majority of absorption (100% of glucose absorption)

Nephron Loop - part of filtration

Separates Na⁺ & H₂O⁺

Distal Tubule (DCT) - part of filtration

Na⁺ & H₂O reabsorption

H⁺ and HCO₃^- (pH regulation)

Collecting Duct - part of filtration

H₂O reabsorption (ADH)

• final concentration of urine

Ureter use

carries urine from kidney to bladder

Bladder use & features

• storage for urine (transition epithelium)

• rugae add to stretch

• smooth muscle (detrusor muscle)

  • wall of bladder

Urethra features

• Internal sphincter - involuntary

• External Sphincter - voluntary

Micturition Reflex

stretch receptor for urination

Gonad definition and parts

• Primary sex organ

  • house reproductive cells: gametes

• Man: testes (spermatid)

• Woman: ovaries (ova)

mitosis vs meiosis

mitosis - two identical (diploid) creates 2

meiosis - genetically unique (haploid) creates 4

Reproductive hormones

Man - Testosterone

Woman - Estrogen & Progesterone

Sex Development

Embryo: bipotential genitalia

• XX: woman — XY: man

  • XY holds SRY gene (on Y chromosome)

    • SRY gene causes development of testes

      • testes release testosterone

        • testosterone creates male reproductive system

      • testes secrete AMH

        • AMH causes degeneration of female components

  • XX no SRY gene

    • develop to default female genitalia

Female Reproductive System Parts

Ovaries: ova

Internal Genitalia: fallopian tubes, uterus, vagina

External Genitalia: erectile tissue, mammary glands

Ovary Follicles

ovum get surrounded by follicular cells

what is oogenesis

development of ovum

• occurs in utero

  • mitosis then stops -never starts again

  • meiosis then stops

what is foliculogenesis / ovarian cycle

process of follicular growth

• leads to ovulation (release of ova)

• recruitment: 10-20 follicles start to develop

  • All will die but 1 (which ovulates)

  • Driven by estrogen & progesterone

    • produced by follicles

what is ovulation?

when an egg is released into abdominal cavity

• drawn in by cilia on fallopian tube into the infundibulum

  • ampulla: where fertilization occurs

• travels down tube to the uterus

  • pushed by cilia & smooth muscle

Regions of the Uterus

Fundus (superior), body(middle) - implantation occurs here, cervix (inferior)

Uterus Wall Layers (inner to outer)

1. endometrium: innermost

   • growth and sloughing during menstrual cycle

   • implantation

2. myometrium: middle muscle (smooth)

3. perimetrium: connective layer (CT)

Uterine Cycle Phases

lasts 28 days on average

1. Proliferative - growth of endometrium

   • estrogen

2. Secretory - linked to ovulation

   • prepares endometrium for implantation

   • progesterone

3. Menstrual: if egg unfertilized

   • lowers estrogen, lowers progesterone

   • endometrium dies away (blood)

Female External Genitalia

Erectile Tissue: clittoris, bulb of vestibule, labia minora

• becomes engorged and highly sensitive

Glands

Mammary Glands

• Alveoli - produce milk (lactogenesis)

  • empty into lactiferous ducts → lactiferous sinus → nipple

Male Reproduction System

Testes: sperm

• seminiferous tubules: spermatogenesis

  • mitosis and meiosis

• epididymis: site where sperm matures and is stored

Male Ejaculation

Vas Deferons →(spermatic cord) → Ejaculatory Duct → Urethra

Male reproductive glands

All constitute semen

• bulbourethral glands

• prostate gland

• seminal vesicles

Penis Parts

3 sets of erectile tissues - engorges with blood