GI Flashcards
Below the upper third of the oesophagus is a four-layered tube
* 1st Layer (inner mucosal layer)
- Made up of a lining epithelium
- An underlying connective tissue called lamina propria
- Muscularis mucosae (smooth muscle)
Functions:
* Production of the mucus that lubricates and protects the inner surface of the alimentary canal
* Secretion of digestive enzymes and substances that break down food
* Absorption the breakdown products of digestion
* Maintenance of a barrier to prevent the entry of noxious substance and pathogenic organisms
Below the upper third of the oesophagus is a four-layered tube
* 2nd layer
* Also known as submucosal layer
- consists of dense connective tissue and aggregates of adipose tissue
- Contains the blood vessels, nerves, and structures responsible for secreting digestive enzymes
- Deliver their secretions either directly to the lumen of mucosal glands or via ducts that pass through the mucosa to the luminal surface
Below the upper third of the oesophagus is a four-layered tube
3rd layer
* Refer as muscularis externa
- Consists of inner layer of circularly smooth
muscle and outer layer of longitudinally
smooth muscle - Facilitate movement of contents of the GI
tract
Below the upper third of the oesophagus is a four-layered tube
* 4th layer
Also known as serosal layer
- Consists of the mesothelium which is
comprised of a layer of simple squamous
epithelium - This is the outermost layer of organs that are
suspended in the peritoneal cavity - It is continuous with the parietal peritoneum
and mesenteries that make up the ventral and
dorsal abdominal wall
A layer of fatty peritoneum
Greater Omentum
(* Hangs from the stomach over the anterior
surface of the transverse colon and the small
intestine
* When inflammation develops in the intestinal
wall, with many lymph nodes of greater
omentum → tends to adhere to the site,
walling off the inflammation and temporarily
localize the source of the problem
* Inflammation of the omentum and peryton
may lead to scar tissue and formation of
adhesions between structures in the abdominal
cavity, such as restrict motility and may lead to
obstruction)
Muscle Layer of alimentary canal
* ___ layers of smooth muscle (involuntary muscle)
* Consists of blood vessels, lymph vessels and a
plexus (network of sympatric and parasympathetic
nerves) which refers as ____ plexus
* Contraction and relaxation of these muscle layers
occur in waves which push the contents of the tract
onwards, called “peristalsis” which under the
influence of sympathetic and parasympathetic nerve
* The contraction helps food mixes with digestive
juices
* Onward movement of contents of the tract is
controlled by sphincters, which prevents backflow in
the tract, allows time for digestion and absorption to
take place
2, myenteric
The activity of breaking down foodstuff by chewing is called _____
mastication
Salivary secretion from the _____, sublingual and submandibular glands
parotid
pH of saliva:
5.8 – 7.4
Swallowing Process
___ stage:
* With the mouth closed, the voluntary muscles of the tongue and cheeks push the bolus
backwards into the pharynx
____ stage:
* When food is swallowed, the soft palate closes the nasal passages and the epiglottis moves over the glottis to close the larynx and the trachea. This allows the foodstuff to move down the oesophagus and prevent aspiration
____ stage:
* The presence of the bolus in the pharynx stimulates a wave of peristalsis that propels the bolus through the oesophagus to the stomach
Oral, Pharyngeal, Oesphageal
Stomach is divided into 3 regions:
- The fundus
- The body
- The pylorus
Pyloric sphincter, guarding the opening
between the stomach and the duodenum:
When the stomach _____ → pyloric sphincter is relaxed and open
When the stomach ______ → the sphincter is closed
is inactive, contains food
3 smooth muscle layers of stomach:
- An outer layer of longitudinal fibres
- A middle layer of circular fibres
- An inner layer of oblique fibres
Gastric juice contains:
Water:
(Further liquefies the food swallowed)
Mucus:
(Lubricates food in preventing mechanical injury to the stomach wall)
(Acts as a barrier between the stomach wall and the highly corrosive gastric juice)
Hydrochloric acid:
(Acidifies the food and stops the action off salivary amylase)
(Kills ingested microbes)
(Provides the acid environment needed for the action of pepsins)
Intrinsic factor (a protein):
(Helps in the absorption of vitamin B12 from the ileum)
Pepsinogen
(It is activated to pepsins by hydrochloric acid)
(These enzymes begin the digestion of proteins, breaking them into smaller molecules)
(Pepsins have evolved to act most effectively at a very low pH, 1.5 and 3.5)
餐後嘔吐、早飽感:
postprandial vomiting, early satiety
