Part B Digestive System

From mucosa of jejunum in response to fats, increases contractility of gallbladder to release bile

Cholecystokinin (CCK)

From mucosa of duodenum in response to acid

Secretin

From mucosa of upper small intestine in response to fats to decrease peristalsis

Gastric inhibitory peptide

How does peristalsis or "forward flow" work?

Distension, coordinated contraction of circular and longitudinal muscles

How does mixing work?

Movement within the biomass of the digesting contents themselves

Defects in ________'s plexus lead to malabsorption

Meissner’s

Goals of chewing: (2)

1. Lubricate food with saliva, 2. Decrease size to facilitate swallowing

What two nerves regulate the swallowing reflex and where?

Coordinated by CN 9/10 in medulla

Step 1 of swallowing reflex:

Nasopharynx closes, breathing inhibited

Step 2 of swallowing reflex:

Laryngeal muscles contract, glottis closes, larynx elevated

Step 3 of swallowing reflex:

Peristalsis in pharynx, upper esophageal sphincter relaxes

What are the three narrowings of the esophagus?

1. Upper sphincter, 2. Aortic narrowing, 3. Diaphragmatic narrowing

The esophagus starts at level __ vertebra and lies on vertebral column

level of C6 vertebra

Esophagus passes through diaphragm via ______ _____ at level of ___

Esophageal hiatus at level T10

Aorta and inferior vena cava pass through the diaphragm at ___ and __, respectively

Aorta at T12, IVC at T8

What part of esophagus can act as sphincter to prevent gastric acid reflux?

Distal part

Where esophagus enters the stomach

Cardia

The esophagus is innervated by

Both sympathetic and parasympathetic (vagus)

Step 1 of esophageal motility:

Upper esophageal sph relaxes to allow food to enter

Step 2 of esophageal motility:

Upper esophageal sph contracts to prevent food reflux into pharynx

Step 3 of esophageal motility:

Primary peristaltic contraction to push food down

Step 4 of esophageal motility:

Secondary peristaltic contraction clears esophagus of remaining food

Step 5 of esophageal motility:

Relaxation of lower esophageal sph via vasoactive inhibitory peptide (VIP)

Step 6 of esophageal motility:

Relaxation of orad region of stomach to allow food bolus

What part of the esophagus that becomes nonfunctional can cause gastric reflux?

Lower esophageal sphincter (LES)

Lower esophageal sph cannot close completely, aperistalsis due to abnormal innervation of enteric system, dysphagia, dilated upper esophageal sph

Achalasia (cardiospasm)

Condition where distal end of esophagus is closed

Esophageal atresia

Condition where there is a hole between esophagus and trachea

Tracheoesophageal fistula

Which disorder causes newborn coughing after breastfeeding?

Tracheoesophageal fistula

Which disorder causes newborn vomiting after breastfeeding?

Esophageal atresia

Esophageal cancer is increased by: (2)

1. Opioids, 2. Hot tea

Protrusion of part of the stomach into mediastinnum through esophageal hiatus of diaphragm

Hiatal hernia

Abdominal part of esophagus, cardia, part of fundus slide up through esophageal hiatus

Sliding hiatus hernia

Fundus and peritoneum passes through esophageal hiatus, cardia does not

Paraesophageal hiatus hernia

This type of hiatal hernia causes regurgitation and heart burn

Sliding hiatus hernia

This type of hiatal hernia causes only retrosternal pain

Paraesophageal hiatus hernia

Gastric reflux and retrosternal pain only happens for how long?

5-10 minutes

Operation used to correct gastroesophageal reflux by wrapping fundus around lower part of esophagus

Fundoplication

Operation to burn tissue around lower esophageal sphincter which becomes thicker and prevents herniation

Radiofrequency treatment

What quadrant is the stomach in?

Upper left quadrant

Pathway of stomach: (5)

Cardia, fundus, body, pyloric part, pyloric sphincter

Notch at the top of stomach by cardia

Cardiac notch

Notch at the bottom part of stomach by pylorus

Angular notch

Three parts of pylorus?

Antrum, canal, sphincter

This region includes the fundus and proximal body of stomach

Orad region

This region includes the antrum and distal part of stomach, mixes food and propels into duodenum

Caudad region

The muscle layer of the stomach is called ____ ________

Tunica muscularis

Stomach has three types of muscle cells

Circular, longitudinal, and oblique

Three motor functions of stomach:

1. Storage, 2. Chyme (mechanical digestion), 3. Controlled rate of passage of food to duodenum

The fundus contains 3 types of cells:

1. Mucoid, 2. Chief, 3. Parietal

Which cell type produces pepsinogen?

Chief cells

Which cell type produces HCl and intrinsic factor?

Parietal

This hormone stimulates acid secretion and growth of parietal cells

Gastrin

Gastrin is produced by

G cells

Condition where gastrin oversecretion by non-β- cell tumors in pancreas causes ulcers in stomach

Zollinger-Ellison syndrome

Hormone in duodenum that inhibits HCl secretion

Secretin

Enzyme in stomach used to breakdown food

Pepsinogen

Endocrine cells in antrum produce 4 hormones:

1. Histamine, 2. Somatostatin, 3. Gastrin, 4. Serotonin

Gastric secretion by vagus nerve, activated by senses even if stomach is empty

Nervous secretion

Gastric secretion stimulated by food ingestion

Gastric / digestive secretion

Cell type that secretes mucus

Goblet cells

Pepsin is activated by

HCl (turns into pepsinogen)

Cell type that secretes somatostatin

D cells

Cell type that secretes cholecystokinin

I cells

Cell type that secretes secretin

S cells

Step 1 of gastric motility:

Orad region relaxes to accomodate food

What mediates receptive relaxation for gastric motility?

CCK

Step 2 of gastric motility:

Caudad region contracts, mixes with gastric secretions

Step 2a of gastric motility:

Slow waves in caudad depolarize smooth muscle

Step 2b of gastric motility:

Action potential and contraction if threshold is reached

Step 2c of gastric motility:

Wave of caudad contraction closes distal antrum, pushes food into stomach to be mixed

Step 2d of gastric motility:

Vagal stimulation (parasym) increases gastric contraction; (sym) decreases it

Contractions at 90 minute intervals to clear stomach of residual food (even during fasting)

Migrating myoelectric complex

What regulates the migrating myoelectric complex?

Motilin

Which region of stomach contracts to propel food into duodenum?

Caudad region

Fat inhibits gastric emptying by the release of what hormone?

CCK

Peristaltic waves create a gradient of food. The ____ ________ chyme is sent to the antrum

Most digested chyme

What is the peristaltic pump?

Intense waves that force chyme through pylorus in bursts into duodenum

(Parasym or Sym) Stimulates gastric motility of longitudinal muscles

Parasympathetic

(Parasym or Sym) Activates gastric secretions

Parasympathetic

(Parasym or Sym) Sensory for gastric reflexes

Parasympathetic

(Parasym or Sym) Inhibits peristalsis, secretions

Sympathetic

(Parasym or Sym) Causes pyloric contraction

Sympathetic

(Parasym or Sym) conveys pain

Sympathetic

What treatment is used for gastric ulcers that don't respond to medication?

Vagotomy