BIO 222 Lecture7.DigestiveSystemAnatomy.Pops - Part1 Review

BIO 222 Anatomy & Physiology 2

aka Gastrointestinal System

digestive system

aka alimentary canal

GI tract

Mouth → pharynx →esophagus →stomach →small intestine → large intestine.

~5-7 meters long.

Muscles in state of tonus.

GI tract

sustained contraction

tonus

Accessory organs/structures

teeth

tongue

salivary glands

liver

gall bladder

pancreas

Physical break down of food.

Assist in chewing/swallowing.

teeth

tongue

No contact with food.

Produce or store secretions that aid in the chemical breakdown of food.

salivary glands

liver

gall bladder

pancreas

Digestive System Process

ingestion

secretion

mixing and propulsion

digestion

absorption

defecation

Taking foods/liquids into mouth

ingestion

Release of H₂O, acid, buffers, hormones, and enzymes into the lumen of the GI tract

secretion

Alternating contractions & relaxation of smooth muscle to churn food & move through GI tract.

peristalsis.

mixing and propulsion (motility)

Mechanical & chemical breakdown of food

digestion

Passage of digested products from GI tract into blood and lymph

absorption

Elimination of feces (stool)

defecation

Connecting Folds

peritoneum

Important Connecting Folds:

mesentery

mesocolon

falciform ligament

omentums

connects to small intestine

mesentery

connects to large intestine

mesocolon

connects liver to diaphragm and anterior abdominal wall

falciform ligament

“general” connective fold; supports adipose tissue

omentums

Deepest layer.

Mucous membrane.

mucosa

Mucosa 3 distinct layers:

epithelium

lamina propia

muscularis mucosae

exocrine cells (secrete mucus); enteroendocrine cells (secrete hormones)

epithelium

MALT (mucosa-associated lymphatic tissue)

lamina propia

Smooth muscle; folded in some areas for maximum SA

muscularis mucosae

Binds mucosa to muscularis

submucosa

regulates movement of mucosa & controls its secretions

submucosal plexus

Skeletal muscle.

Smooth muscle ( in most of alimentary canal).

muscularis

Mouth, pharynx, parts of esophagus, & external sphincter

skeletal muscle

aka Auerbach’s plexus

myenteric plexus

controls motility of GI tract

myenteric plexus

in digestive organs outside the peritoneal cavity

adventitia

aka visceral peritoneum

serosa

if in the peritoneal cavity; covers the intra-abdominal organs

serosa

Oral cavity

uvula

tongue

Salivary Glands

parotid

sublingual

submandibular

Pancreas

pancreatic duct

Colon

transverse colon

ascending colon

descending colon

Small intestine

duodenum

jejunum

ileum

Digestion begins here.

Ingestion.

Secretion.

Digestion.

Propulsion (into pharynx).

Part of canal.

Houses teeth, tongue, 3 pairs of salivary glands.

Food becomes bolus.

oral cavity or mouth

Food becomes

bolus

Central and lateral

incisors

aka cuspids

canines

Premolars and molars

molars

Three components of teeth:

crown

root

neck

visible portion; covered with enamel

crown

embedded w/in the alveolus; covered with cementum

root

junction between the root & crown

neck

Almost all calcium hydroxyapatite crystals.

Hardest substance in body.

Can’t repair damaged enamel.

enamel

majority of tooth.

~70% calcium hydroxyapatite.

2nd hardest substance in body.

Formed throughout life via odontoblasts.

dentin

encased by dentin.

Soft, inner gelatinous substance.

Extends into root via root canal.

pulp

opening at base of root through which blood & lymphatic vessels & nerves enter

apical foramen

3 pairs (major glands)

parotid

submandibular

sublingual

Use parotid duct to secrete saliva.

~25-30% of total saliva.

parotid

Use submandibular duct to secrete.

~65-70% of total saliva.

submandibular

Use several small sublingual ducts to secrete.

~5% of total saliva.

sublingual

main component (99.5%)

water

Na⁺, Cl^-, K⁺

electrolytes

saliva enzymes

salivary amylase

lingual lipase

lysozyme

First enzyme food encounters.

Catalyzes carbohydrate (starch) breakdown.

salivary amylase

Secreted by lingual glands in tongue (begins working after food is swallowed)

lingual lipase

Fights against pathogenic bacteria; damages cell membranes

lysozyme

Antibody; binds to specific antigens on pathogens & prevents them from penetrating epithelium

secretory IgA

Will neutralize any acids from the stomach that have regurgitated into the esophagus.

Will buffer any acidic foods.

bicarbonate ions

First stage in defense against pathogens.

Chemical digestion.

Mechanical digestion.

Moistens, lubricates, cleanses oral mucosa.

Saliva General Functions

Salivary amylase

chemical digestion

Formation of bolus

mechanical digestion

Paramyxovirus attacks parotid glands.

Inflammation & enlargement of the parotid glands.

Vaccine in 1967 = incidence of disease has declined dramatically.

mumps

3 divisions of Pharynx (throat)

nasopharynx

oropharynx

laryngopharynx

From uvula to epiglottis.

lined with stratified squamous to protect from abrasion.

oropharynx

From hyoid bone to esophagus.

lined with stratified squamous to protect from abrasion.

laryngopharynx

lies posterior to trachea.

~25cm long (~10 inch).

Propulsion (Transfers bolus to stomach).

Limited secretion.

Mucosa is lined with stratified squamous.

esophagus

3 phases of swallowing (deglutition)

voluntary

pharyngeal

esophageal

aka buccal phase

voluntary

Only phase under conscious control.

Tongue pushes bolus toward oropharynx.

voluntary

Involuntary control.

Controlled by swallowing reflex (initiated in medulla oblongata of brain).

Bolus contacts sensory receptors in oropharynx to trigger reflex.

Uvula and soft palate elevate & close off nasopharynx.

pharyngeal

Epiglottis closes

prevent aspiration

Involuntary control.

upper esophageal sphincter relaxes → neurons trigger muscularis to undergo peristalsis.

Peristaltic waves move bolus down esophagus.

esophageal

Lower esophageal sphincter fails to close adequately.

Stomach contents reflux – including the HCl.

The HCl irritates the lining of the esophageal wall = heart burn!

Gastroesophageal Reflux Disease (GERD)

5 anatomical regions of the stomach:

cardia

fundus

body

pyloricantrum

pylorus

Esophagus empties into this.

Gastroesophageal sphincter (aka lower esophageal sphincter or cardiac sphincter) must relax for bolus to enter.

cardia

Dome-shaped top

fundus

Largest portion

body

Inferior portion

pyloric antrum

connects antrum & pylorus

pyloric canal

Terminal portion.

Empties into duodenum of small intestine.

Pyloric sphincter.

pylorus

THREE layers of smooth muscle in the stomach

longitudinal muscle layer

circular muscle layer

oblique muscle layer overlying mucosa

churning = turns food into

chyme

Secrete ACIDIC mucus

mucous neck cells

Secrete HCl.

Produce intrinsic factor (needed for absorption of B12 – typically absorbed in small intestine).

parietal cells

Secrete inactive pepsinogen (becomes active pepsin when encounters acidic pH = for protein digestion.

Secrete gastric lipase = for lipid digestion)

chief cells

Secrete hormones

enteroendocrine cells

Condition in which the body cannot absorb enough Vitamin B12, because it lacks intrinsic factor.

pernicious anemia

3 divisions of the small intestine

duodenum

jejunum

ileum

important area for chemical digestion

duodenum

Secretions from gall bladder & pancreas enter through this

major duodenal papilla

Produce an alkaline mucus

duodenal (Brunner’s) glands

important area for absorption of nutrients

jejunum

Terminates at the cecum (part of large intestine)

ileum

sphincter; controls movement of material into cecum from ileum

ileocecal valve