Ch 26 Digestive System

digestive system is composed of the _____ & ______.

• gastrointestinal (GI) tract

• Accessory digestive organs

GI Tract

continuous tube: from oral cavity to anus

Accessory Digestive Organs

structures that secrete stuff into Gi tract, assisting in breakdown of food

structure of the GI (tract)

• oral cavity

• pharynx

• esophagus

• stomach

• large intestine

• small intestine

• anus

Structures of the Accessory Digestive organs

• parotoid salivary gland

• teeth

• tounge

• sublingual salivary gland

• submandibular salivary gland

• liver

• gallbladder

• pancreas

transport of food (2 ways)

• Peristalsis: GI tract moves like a wave

• Segmentation: backward-and forward motiion

2 forms of digestion (breakdown of food)

• mecanical: food is physically broken down (teeth)

• chemical: enzymes break down foor (saliva)

what are the 4 tissue layers of the walls of the GI tract? (deep to superficial)

• Mucosa

• Submucosa

• Muscularis

• Serosa (or adventitia)

Mucosa epithelium type

simple columnar with microvilli

• exception: esophagus

capillaries of the Mucosa layer

llamina propria

Submucosa layer contians

• larger blood & lymph vessels

• submucosal nerve plexus (sympathetic & parasympathetic innervation)

Musclaris layer is made up of

• 2 layers of smooth muscle

• myenteric nerve plexus

The 2 layers of smooth muscle of the Muscularis

• inner circular (circumferentially)

• outer longitudnial (lengthwise)

exception: esophagus & stomach

oral cavity

“mouth”- entrance to GI tract

oral cavity function

• ingestion

• digestion: mechanical & chemical

oral cavity tissue type

stratified, squamous epithelium (non-keratinzed)

structural features of the oral cavity

• cheeks, lips, and palate

• tounge

• salivary glands

• teeth

bolus

food mixed with saliva; semi-solid mass

salivary glands function

secrete saliva

• moistens food-becomes bolus

• begin chemical digestion of starch

• food molecules dissolved for taste

• cleanses oral cavity

• help inhibit bacterial growth (antibacterial substances)

3 Salivary glands

• partoid salivary glands

• submandibular salivary gland

• sublingual salivary gland

Which is the the LARGEST salivary gland?

partoid salivary gland

Which salivary glands secretes the most saliva? and how much?

submandibular salivary gland (65%)

tounge function

mechanincal digestion- grips food with papillae (pumps on tongue)

tonge contains…

taste buds (only some papillae contains tast buds)

pharynx tissue type

nonkeratinized stratified squamous epithelium

What is the Uvulas function during deglutition?

uvula seals off nasoparynx

Esophagus function

propulsion- moving bollous

esophagus tissue type

stratified squamous epithelieum non-keratinized

esophagus exception to histonogy layers?

muscularis

stomach function

• bolus is chemically and mechanically digested

• temporary storage

stomach exception to histology layers

has 3 muscularis layers instead of default 2, inorder to mechanically digest food

• inner oblique layer

• middle ciruclar layer

• outer longitudinal layer

in the stomach the bolus becomes…

chyme (toothpaste type of consistensy)

small intestine function

absorption of 90% of nutrients and water

small intestine tissue type

columnar epithelium with microvilii

duodenum contains

major duodenal papilla- bile & pancreatic juice

where does most digestion and absorption occur?

Jejunum of small intestine

Illeum

connects to cecum (1st part of large intestine) through ileocecal valve

What does the small intestine contain that increases surface area?

• circular folds

• villi

• microvilli

large intestine function

absorption of water from the remaining chyme —> feces

Defecation

when feces is eliminated

exception to histology layers in the large intestine

teniae coli- reduced outer longitudinal layer of muscularis

the 2 esophagus exceptions

• mucosa layer is non-keratinized stratified squamous epithelium

• muscularis layer- includes skeletal muscle

stomach exception to histology layers

muscularis has 3 layers instead on 2

does small intestion have any exceptions to histology layers?

NO (default condition)

large intestine exception to histology layers?

outer layer of musclaris forms teniae coli

liver functions

• produce and secrete bile

• detoxifies- breaksdown drugs and hormones

ducts of the liver

left and right hepatic ducts—> common hepatic duct

gallbladder function

stores, concentrates, and releases the bile that the liver produces

duct of the gallbladder

cystic duct

pancreas function

produce pancreatic juice

pancreatic juice-

• mucin

• digestive enzymes

• bicarbonate

ducts of the pancreas

main pancreatic duct merges with common bile duct