Chapter 24 - Digestive System

What is the alimentary canal also called?

GI tract / digestive tract

What structures make up the digestive tract?

Oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus

What are the accessory organs of digestion?

Teeth, tongue, salivary glands, liver, gallbladder, pancreas

what is the digestive system responsible for?

providing raw materials to support life

what do food molecules do in the digestive system?

catabolize for energy and supply anabolic reactions

what is ingestion?

take in food

what is propulsion?

move food through GI

what is an example of mechanical processing?

chewing

what is chemical digestion?

enzymatic breakdown of large molecules

what are secretions?

enzymes, acids, mucus, water

what is absorption?

move organic molecules from gut to interstitial fluid

what is excretion?

indigestible food ejected from body

what is digestive activity controlled by?

chemical of mechanical stimuli

What are the two modes of control of the digestive system?

Extrinsic and intrinsic

What is the Enteric Nervous System (ENS)?

Nerve plexus of the gut (“gut brain”)

What are short reflexes?

ENS only

What are long reflexes?

input from the ANS

How many hormones regulate digestion?

18

Where are digestive hormones produced?

Enteroendocrine cells in the GI tract

What do local mechanisms use to trigger secretion?

Prostaglandins and histamine

Where are most digestive organs located?

Peritoneal cavity in the abdomen

What lines the peritoneal cavity?

Parietal peritoneum

What covers the digestive organs?

Visceral peritoneum

Why do peritoneal layers secrete fluid?

To reduce friction during movement

What is ascites?

Excess peritoneal fluid causing abdominal swelling

What is peritonitis?

Inflammation of the peritoneum due to damage or infection

What are mesenteries?

Sheets of peritoneum that support digestive organs

What are retroperitoneal organs?

Organs anchored to the body wall

What do mesenteries contain besides organs?

Blood vessels, lymphatic vessels, nerves, and adipose

What does the lesser omentum hold?

stomach

What does the falciform ligament hold?

liver

What does the greater omentum hold?

intestine

What happens to GI venous blood?

Enters hepatic portal circulation

Why does blood go to the liver first after digestion?

Liver processes or absorbs nutrients before blood returns to circulation

what are waves of contraction that move the food bolus along the gut called?

peristalsis

Single-point contractions that chop up the bolus and allow enzymes access to inner regions are called ….

segmentation

How does the parasympathetic nervous system affect digestion?

Increases muscle activity and secretion

How does the sympathetic nervous system affect digestion?

Decreases muscle activity and secretion

what allows extrinsic control of digestive activity?

ENS and ANS

What does the oral cavity connect?

Environment to pharynx

What type of epithelium lines the oral cavity?

Stratified squamous epithelium

What are the walls of the oral cavity made of?

Muscular cheeks

What structure forms the floor of the oral cavity?

tongue

What forms the roof of the oral cavity?

hard and soft palate

What is the role of the soft palate during swallowing?

Closes off the nasopharynx

What type of tissue is the tongue made of?

muscular

What covers the surface of the tongue?

papillae

What do papillae provide?

Friction and house taste buds

What secretion from the tongue lubricates food?

mucin

What secretion from the tongue starts lipid digestion?

Lingual lipase

Saliva is mostly what?

water

What enzyme in saliva digests starch?

amylase

What substance in saliva provides lubrication?

mucin

What immune components are found in saliva?

antibodies and antimicrobials

What is the role of saliva in oral hygiene?

Cleanses mouth and controls oral bacteria

How does saliva help taste?

Dissolves food chemicals

How does saliva help swallowing?

Moistens food for bolus formation

What digestion begins in the mouth?

Chemical digestion of carbohydrates

What effect does saliva have on oral pH?

buffers oral pH

How does the parasympathetic nervous system affect saliva production?

increase secretion

How does the sympathetic nervous system affect saliva production?

decrease secretion “dry mouth”

Where are the parotid salivary glands located?

Inferior to the zygomatic arch

What do the parotid salivary glands secrete?

thick secretion, high salivary amylase

Where are the sublingual salivary glands located?

Inferior to the tongue

What do the sublingual salivary glands secrete?

watery secretion, high in buffers

Where are the submandibular salivary glands located?

Posterior floor of the mouth

What do the submandibular salivary glands secrete?

buffers, mucin, amylase

What is the main function of teeth?

Mastication and mechanical digestion

Soft center containing blood vessels and nerves in connective tissue (pulp) is called the … …

pulp cavity

Bone-like tissue surrounding the pulp cavity containing odontoblasts that maintain dentin throughout life is called …

dentin

What covers the crown of a tooth?

Enamel composed of hydroxyapatite

What covers the root of a tooth?

cementum

What holds the tooth in the alveolus of the jaw?

periodontal ligaments

what are incisors used for?

cutting

what are cuspids/ canines used for?

tearing and piercing

what are bicuspids / premolars used for?

crushing, mashing, grinding

what are molars used for?

crushing, grinding

what are your 3rd molars called?

wisdom teeth

how many deciduous teeth do you have under the age of 12?

20

how many permanent teeth do you have by age 21?

32

a tooth that fails to erupt and remains in the jaw, causing pain, often requiring surgical removal is a … …

impacted tooth

Demineralization of enamel and dentin by bacteria, exposing nerve and causing pain causes … …

dental caries

Infection of gingiva with an immune response eroding bone around teeth, leading to tooth loss is called …. …

periodontal disease

what part of the pharynx is at the back of the mouth?

oropharynx

what part of the pharynx is located superior to the voice box?

laryngopharynx

What does the pharynx connect?

Oral cavity to esophagus

Why is the pharynx considered a shared space?

Shared with the respiratory system

What type of epithelium lines the pharynx?

Stratified squamous epithelium

What structures are found in the lamina propria of the pharynx?

Tonsils and mucus glands

What type of muscle surrounds the pharynx for swallowing?

Skeletal muscle

what is the muscular tube that connects the pharynx to the stomach?

esophagus

What is the inferior constriction point of the esophagus called?

Gastroesophageal sphincter

Gastric juice regurgitates into the esophagus, causing erosion. this is called ….

heartburn

What type of epithelium lines the esophagus?

Stratified squamous epithelium

Why does the esophagus have large folds in the mucosa and submucosa?

To keep the lumen closed during rest

What do esophageal glands in the submucosa secrete?

Mucus to reduce friction

What type of muscle is found in the upper 2/3 of the esophagus?

skeletal

What anchors the esophagus in place?

adventitia

Which phase of swallowing is voluntary?

buccal

What happens to the soft palate during the buccal phase?

It is raised to protect the nasopharynx