Biol 204 Exam 1 lecture 1

Major organs of the digestive system

Oral cavity

pharynx

esophagus

stomach

small intestine

large intestine

anus

Acessory organs of digestive system

Teeth

tongue

salivary glands

liver

gallbladder

pancreas

alimentary canal

same thing as digestive tract

whole passage from which food moves from mouth to anus

Gastrointestinal tracts

Stomach + intestines

ingestion

intake of food

propulsion

movement of bolus through swallowing or peristalsis

Mechanical digestion

physical breakdown of food (mastication / muscular contractions )

Chemical digestion

physical breakdown of food with enzymes/ acids

Absorption

uptake of nutrient molecules

(villi help intestine absorb important nutrients)

Compaction

absorbing water and consolidating the residue into feces

Defecation

elimination of feces

Physiological processes of the digestive system

ingestion

propulsion

mechanical digestion

chemical digestion

absorption

compaction

defactation

Digestive functions of oral cavity

ingestion: food enters the digestive tract

mechanical digestion: mastication

Chemical digestion: salivary enzymes

Sensory evaluation: Taste, texture, and temperature

Initiation of swallowing: Tongue pushes bolus into the pharynx

amylase

salivary enzyme that begin carb digestion

Bolus

food ball mixed with saliva

How much teeth are in each part of the Jaw

16

Incisor

blade shaped located in the front of the tooth, used for clipping or cutting

1 root

canine

Cuspids

pointed for puncturing and shredding

1 root

Premolar

1-2 roots

broad and lumpy for crushing shredding and grinding

molar

2-3 roots

broad and lumpy for crushing shredding and grinding

Crown

neck

root

Root canal

passageway for blood vessels and nerves to the pulp cavity

Enamel

hard coating of the crown, non living, made of hydroxyapatite crystals

hydroxyapatite crystals

make up enamel

contain calcium and phosphate

what are hydroxyapatite crystals made of

in enamel

calcium and phosphate

is the enamel living tissue?

false

cementum

Bone like material covering the roots that anchor the tooth to the bone

Dentin

yellowish tissue that makes up the bulk of teeth

offers strong support to enamel due to elasticity

% hydroxyapatite in dentin

70

Pulp

mass of loose connective tissue,

blood

lymphatic vessels

and nerves

Pulp function

tooth sensation

dentin formation

Odontoblasts

cell bodies responsible for dentin formation

in pulp, odontoblast process into the dentin

dentinal tubules

contain odontoblast process and dentinal fluid

channels that run from pulp to beneath the enamel

Odontoblast processes

cytoplasmic extensions emanating from odontoblasts extending into dentin

Does dentin have never fibers?

no

Extrinsic Salivary glands

Major glands

parotid, submandibular, sublingual

stimulated by food

How much saliva do Extrinsic Salivary glands make

1-1.5 L of saliva, stimulated by food

Intrinsic Salivary glands

small glands dispersed through oral tissues

secrete saliva continuously in small amounts

for lubrication and oral health

Composition of saliva

Water

electrolytes (buffer saliva)

mucus

enzymes (begin carb digestion)

antimicrobial substances

Functions of saliva

Lubricates food and helps to swallow

begins carb digestion

facilitates taste

protects oral tissues and teeth

buffers acids in moth

Electrolytes in saliva

Na+ K+ Cl- HCO3-

Deglutition

Mechanism of swallowing involving 22 muscles coordinated by the swallowing center

Proce

Deglutition phases

oral

pharyngeal

e

Oral Deglutition phase

Under voluntary control

tongue compacts food and saliva into a bolus, pushes it into laryngopharynx

Pharyngeal Deglutition phase

Bolus moved through the pharynx into the esophagus

larynx rises so epiglottis blocks the trachea

Epiglottis during pharyngeal phase

Esophageal phase

Bolus pushed down toward stomach by peristalsis

Cardiac sphincter opens after food enters the stomach, the sphincter closes, which prevents regurgitation.

4 layers of digestive tract

Mucosa

Submucosa

Muscularis Externa

Serosa/Adventitia

All organs have the same basic pattern of tissue layers in their walls

Mucosa

One of the 4 layers of the digestive tract

1st layer

Consists of

epithelium

lamina propia

muscularis mucosae

Submucosa

One of the 4 layers of the digestive tract

2nd layer

Muscularis Externa

One of the 4 layers of the digestive tract

3rd layer

1. inner circular later

2. outer longitudinal layer

Serosa / Adventitia

One of the 4 layers of the digestive tract

4th later

Serosa : organs inside peritoneal cavity

Adventitia: organs outside the peritoneal cavity

epithelium

In mucosa, the 1st layer

lamina propia

In mucosa, the 2nd layer

muscularis mucosae

In mucosa, the 3rd layer

inner circular layer

In muscularis externa, the 1st layer

outer longitudinal layer

In muscularis externa, the 2nd layer

Enteric NS

NS of GI tract

embedded in walls of the digestive and includes two plexuses (network of nerves) as well as their associated ganglia

Myenteric (auerbach’s) plexus

Between circular and longitude layers of muscularis

Control of motility and movement of digestive tract (peristalsis)

submucosal (Meissner’s) plexus

in submucosa

regulate GI secretions

Peristalsis

Coordinated wave of muscle contraction and relaxation that pushes food forward

In esophagus

stomach

intestine

Rule of peristalsis

contract behind bolus

relax in front of bolus

Where does peristalsis happen

esophagus

stomach

intestine

long reflex

central loop

Short reflex

local loop

Saliva is composed of approximately 99%

water

electrolytes found in saliva

sodium, potassium, chloride, Bicarbonate

The glycoproteins responsible for the viscous quality of saliva are called

mucins

The enzyme that begins carbohydrate digestion in the mouth

salivary amylase

Saliva contains antimicrobial substances such as

immunoglobulin A, lysozymes

what is deglutition regulated by?

the medulla