UNIT 5 - Digestive System

functions of digestive system

breakdown food

absorb nutrients

excrete waste

process of nutrient redemption

ingestion

secretion, motility, digestion, & absorption

defecation

ingestion

to bring food/liquid into your body

secretion

saliva and acid is secreted and used to break down food

motility

churning and pushing things down digestive canal

expose the things to epithelium

digestion

breaking down complex nutrients into simple nutrients

absorption

bringing minerals, nutrients, & more into your blood

defaction

getting rid of waste

digestive canal

continuous tube where the actual food/liquid moves

accessory digestive organs

parts that don’t actively touch the actual food/liquid

mesentery

facia that hold digestive organs together

layers of the digestive tract

(inner to outer)

lumen

mucosa

submucosa

muscularis externa

serosa

mucosa

epithelium

lamina propria (structural support)

muscularis mucosae (smooth muscle)

submucosa

houses blood & lymphatic vessels

submucosal nerve plexus (sensory neurons & chemo receptors that’re important for motility)

muscularis externa

circular & longitudinal layer (named after its orientation)

myenteric nerve plexus (contracts muscles)

serosa

epithelium

connective tissue

cell types of the digestive system

nonkeratinized stratified squamous → columnar (@ stomach & s. intestine) → squamous (@ anus)

parts of mouth

cheeks, lips, palate, uvula, teeth, salivary glands, tongue

cheeks

has buccinator muscles that aid w/chewing

lips

has orbicularis oris that aid w/chewing

palate

roof of mouth that consists of bony/hard palate & soft/muscular palate that aid in swallowing, speech prod., & saliva secretion

uvula

teardrop-shaped tissue hanging from soft palate’s center

teeth

aid in crushing, grinding, and tearing food

salivary glands

prod. saliva to aid in lubricating food

saliva

made up of 99.5% H2O and 0.5% solutes whcih include ions, lysozyme, immunoglobulin A, & amylase (Cl-)

usually produced autonomically

types of salivary glands

Parotid gland (CN IX)

Sublingual gland & Submandibular gland (CN VII)

tongue

has extrinsic and intrisic muscles (controlled by CN XII) to aid with speech and swallowing

extrinsice tongue muscles

in charge of side-to-side & in/out movement

helps w/manuvering food into bolus & swallowing

intrinsic tongue muslces

in charge of altering shape & size of tongue

helps w/swallowing & speech

steps of swallowing

1. voluntary stage

2. pharyngeal stage

3. esophageal stage

voluntary (oral) stage

food is chewed, mixed with saliva, & formed into bolus

tongue elevates and presses against hard palate to move bolus to oralpharynx

pharyngeal stage

initiated when bolus touches palatoglossal arch

soft palate rises to block nasal cavity & epiglottis flips down to block larynx

pharyngeal contracts to move bolus to esophagus

esophageal stage

bolus is moved towards stomach via peristalsis (automatic wave-like muscle contractions in esophagus)

functions of stomach

stores food

mechanically & chemically breaks down food

anatomy of stomach

gastric fold, pits, and glands

gastric folds (rugae)

microscopic folds found in stomach lining

gastric pits

surface invaginations formed by gastric pits

gastric glands

cells that secrete things into stomach lumen

EX: mucous neck cells, parietal cells, chief cells, & G cells

mucous neck cells

secrete mucus

parietal cells

secrete HCl and intrinsic factors

chief cells

secrete pepsinogen (in its inactive form until it reaches low pH to protect from randomly destroying amino acids) and gastric lipase

G cells

secrete gastrin

propulsion

peristaltic waves to push chyme towards the pylorus

retropulsion

when the pyloric sphincter closes, forcing larger food particles backwards for further mixing & grinding

vomiting

forceful expulsion of stomach contents

GERD stomach

gastroesophageal reflux disease

when stomach acid frequently flows back into esophagus (caused by weakend lower esophageal sphincter)