11: GT tract and oral cavity and oesophagus

Learn componenets

learn components

What is the peritoneum?

What is peritonitis?

Disease of the peritoneum- accumulation of peritoneal fluid

Abdominal swelling+pain

Name 6 functions of the digestive system

Ingestion, mechanical processing, digestion, secretion, absorption and excretion

Function mesentery proper?

Access route for blood/ lymph vessles

Layers of the gastrointestinal tract- alimentary canal?

Mucosa, submucosa, muscularis externa, adventitia

Composition mucosa?

Epithelium and lamina propria

Lamina propria=loose irregulal CT, blood/lymph vessles+ muscularis mucosa

Submucosa composition?

Dense irregular connective tissue

Exocrine glands

Larger blood/lymph vessles

Muscularis externa composition and function function?

Contains circular and longitudinal smooth muscle for peristalsis and segmentation (movement of ingesta).
Controlled by the myenteric nerve plexus; structure and function vary by region.

Serosa composition and function?

Loose irregular CT covered by simple squamous epithelia- outermost layer- found in oesophagus

contains vascular and nervous supplies for GIT

SUMMARY

Mucosa lines digestive tract– Moistened by glandular secretions– Lamina propria and epithelium form mucosa

Submucosa – Layer of dense irregular connective tissue

Muscularis externa – Smooth muscle arranged in circular and longitudinal layers – Adventitia

Serosa – Serous membrane covering most of the muscularis externa

Control of digestive function?

Motility

Rate of digestion/absorption

How are digestive functions controlled?

Enteric nervous system

Enterogasterones- hormones

Name 3 ways food is moves in GIT

Peristalsis

Segmentation

Haustral

Name 3 ways food is moved along the digestive tract

Local mechanisms- response to pH changes

Neural mechanisms- nervous reflexes

Hormonal mechanisms- enhance/inhibit muscle contraction

Control of digestive system?

Control of Digestive Function:

• Short reflexes: Local responses within the GI tract; triggered by local stimuli and act on smooth muscle and glands.

  • Regulated by enterogasterones

• Long reflexes: Involve the CNS; include cephalic reflexes (triggered by sight, smell, thought of food) / afferent signals from the GIT (chemo-, mechano-, and osmoreceptors).

Learn table of gastric hormones

Function of the oral cavity in the GIT

Analysis of food

Mechanical digestion-teeth

Lubrication- mixing mucus+ saliva with food

Limited digestion- chemical digestion

Function oesophagus?

Transport food from pharynx to dtomach

Composition oesophagus?

Walls contain mucosal, submucosal and muscularis layers

Composed of non keratinized stratified squamous epithelium

Has both smooth and skeletal muscle portions

Muscular layers of oesophagus?

Upper third- skeletal muscle

Lower two thirds- smooth muscle

Upper muscle?

Upper esophageal sphincter- skeletal muscle

Lower muscle?

Lower esophageal sphincter- smooth muscle

Mucosa, submucosa muscularis externa and adventitia

Name the 3 phases of swallowing

Buccal phase

Pharyngeal phase

Oesophageal phase

Buccal phase?

Bolus is pressed against the hard palate; tongue pushes it into the oropharynx, raising the soft palate to block the nasopharynx. Reflexes then move the bolus toward the stomach.

Pharyngeal phase?

Begins when the bolus touches the palatal arches and pharyngeal wall.

The larynx elevates and the epiglottis folds to direct the bolus past the closed glottis, while the uvula and soft palate block the nasopharynx.

Oesphageal phase?

The esophogeal phase begins as the contraction of pharyngeal muscles forces the bolus through the entrance to the oesophagus

Once in the oesophagus the bolus is pushed toward the stomach by a peristaltic wave

Dysphagia?

Difficulty swallowing

Barretts oesophagus?

Barrett’s Oesophagus:
A complication of GERD- gastroesophageal reflux disease, caused by acid exposure- reflux. The normal mucosa is replaced by metaplastic columnar epithelium, increasing the risk of oesophageal cancer.