digestive system chapter 22

bio104

digestive system

gastrointestinal tract (alimentary canal) plus accessory organs that break down food into nutrients to be absorbed in the bloodstreamand delivered to body cells in useable form..

alimentary canal

continuous tube consisting of the oral cavity, pharynx, esophagus, stomach, small intestine, large intestine

accessory organs of the digestive system

organs that aid digestion but are not part of the alimentary canal, including the teeth, tongue, salivary glands, liver, pancreas, and gallbladder.

what are the basic functions of the digestive system

ingestion, secretion, propulsion, digestion, absorption, defecation

ingestion

bring food and water into the mouth

secretion

the process of releasing digestive enzymes, hormones, acid and mucus into the digestive tract to aid in food breakdown.

propulsion

the movement of food through the digestive tract, achieved by muscular contractions known as peristalsis.

digestion

mechanical and chemical breakdown of food into smaller components for absorption.

defecation

eliminate waste products from the body through the anus.

motility

the ability of the digestive system to move contents through the digestive tract, largely driven by muscle contractions. mixing, churning, propulsion. regulated by the autonomic nervous system and endocrine hormones

how does the autonomic nervous system affect digestion?

sympathetic nervous system inhibits digestion, parasympathetic nervous system stimulates digestion.

endocrine hormones

chemical messengers that regulate various digestive processes, including motility and enzyme secretion. can inhibit or stimulate digestion.

lumen

concentric layers of tissue surround a spacewithin the digestive tract where food and liquids pass through, playing a crucial role in digestion and absorption.

4 main layers of the tissue in the alimentary canal from deep to superficial

mucosa, submucosa, muscularis externa, serosa(adventitia)

mucosa

the innermost layer of the alimentary canal, responsible for secretion and absorption, including simple columnar or stratified squamous epithelial tissue with goblet cells that secrete mucus.

lamina propria

a layer of connective tissue within the mucosa that supports the epithelium and contains blood vessels, lymphatics, and immune cells.

muscularis mucosae

a thin layer of smooth muscle in the mucosa, responsible for local movements of the mucosal layer and enhancing the absorption and secretion processes.

submucosa

layer of dense irregular ct with blood vessels and submucosal glands

submucosal glands

glands located in the submucosa that secrete digestive enzymes and mucus to aid in digestion.

submucosal plexus (meissner’s plexus)

a network of nerves located in the submucosa that regulates digestive processes such as secretion and blood flow.

muscularis externa

layer of smooth muscle responsible for peristalsis and segmentation in the digestive tract. inner circular and outer longitudinal layers.

myenetric plexus (auerbach’s plexus)

a network of nerves located between the layers of the muscularis externa that coordinates peristalsis and digestive tract motility.

serosa

viseral peritoneal membrane that covers the external surface of the digestive organs, providing protection and support made of simple squamous epithelium and loose ct.

adventitia

outermost dense irregular connective tissue layer of organs not covered by peritoneum, anchoring them to surrounding structures.

outer parietal peritoneum

membrane that lines the abdominal cavity, serving as a protective layer for internal organs.

inner visceral peritoneum

membrane that covers the organs within the abdominal cavity, providing a lubricated surface to facilitate movement and reduce friction.

mesenteries

folds in ther peritoneum between loops of intestines

greater omentum

“fatty apron” that hangs from the base of the stomach made of adipose tissue

lesser omentum

a small fold of peritoneum that extends from the liver to the lesser curvature of the stomach. adipose tissue that protects and insulates

peritonitis

inflammation of peritonium (GI organs) that results from trauma when blood or contents of an abdominal organ leak into peritoneal cavity causing pain, infection and rebound tenderness. It is fatal if left untreated. treatments involve antibiotics and or surgery.

oral cavity

the beginning of the alimentary canal. ingestion, secretion, chemical and mecanical digestion and propulsion posterior to teeth and bounded by cheeks lined with stratified squamous nonkeratinized epithelium. accesory organs are teeth, tongue and salivary glands

bolus

a soft mass of chewed food that is formed in the mouth during the process of digestion, prepared for swallowing.

cheeks

buccinator muscle and oral mucosa that form the lateral walls of the oral cavity, playing a role in manipulation of food during chewing and speech.

lips

obicularis oris muscle covered with stratified squamous keratinized epithelium

labial frenulum

a fold of tissue that connects the inside of the lips to the gums, helping to stabilize the position of the lips.

vestibule

space between lips, cheeks and gums

hard palate

anterior 2/3 made up of maxilla and palatine bone

soft palate

the posterior 1/3 of the roof of the mouth, consisting of muscle and tissue that separates the oral cavity from the nasal cavity.

gingiva

the soft tissue that surrounds the base of the teeth and covers the jawbone, commonly known as gums.

uvula

part of the soft palate prevents food from entering nasal cavity

teeth

organs of mechanical digestion.

mastification

chewing to increase surface area of food. more surface area allows for more nutrients to be absorbed.

alveoli

bony sockets in maxilla and mandible that hold the teeth in place.

dentition formula

a representation of the number and arrangement of teeth in an individual's mouth, typically expressed in a series of fractions.

3214123

3- tricuspids (molars)

2- bicupids (premolars)

1- cuspids (canines)

4- incisors

32 permenant adult teeth

and their respective positions in the dental arch, indicating how many of each type are present. same for top and bottom jaw

crown

the visible part of a tooth above the gum line, covered in enamel, and responsible for chewing and grinding food.

enamel

the hard, outer layer of a tooth that protects it from decay and wear made of hard mineralized substances mostly calcium.

dentin

the layer of a tooth beneath the enamel, making up the bulk of the tooth structure and providing support and protection.

root

the part of a tooth that is embedded in the jawbone and anchors it in place, providing stability and support. below gumline

tongue

skeletal muscle covered with stratified squamous epithelium

lingual frenulum

a thin band of tissue that connects the underside of the tongue that attaches tongue to oral cavity

papillae

tastebudsthat are found on the surface of the tongue. They contain sensory receptors for taste.

4 kinds of tastebuds

filiform (no taste), fungiform, circumvallate, foliate papillae

salivary glands

exocrine glands that produce saliva (water, enzymes,mucous and other solutes), aiding in digestion and mouth lubrication.

parodid glands

The largest salivary glands located over the masseter muscle, which produces 25-30% of saliva that aids in digestion and lubricates the mouth.

submandibular glands

Salivary glands located along the mandible that produce approximately 60-70% of saliva, aiding in digestion and lubrication.

parotid duct

A duct that carries saliva from the parotid glands to the oral cavity, facilitating the digestive process.

submandibular ducts

Ducts that transport saliva from the submandibular glands to the floor of the mouth, aiding in digestion.

sublingual glands

Salivary glands located beneath the tongue that produce 5% of saliva production, important for digestion and lubrication.

sublingual ducts

Ducts that convey saliva from the sublingual glands to the oral cavity, contributing to the digestive process.