GHM L3 Flashcards
What is the GI tract?
Passageway of the digestive system, runs from the mouth to the anus
Describe the tissue structure of the GI tract
- Mucosa
- Submucosa
- Muscularis Externa
- Serosa
- Lumen
- Mesentery
What does the mucosa consist of?
- Epithelium
- Lamina propria
- Muscularis Mocosae
What does the muscularis externa consist of?
Circular muscle
Longitudinal muscle
What does the serosa consist of?
Connective tissue
Epithelium
Different parts of mouth
- Lips + cheeks
- Palate
- Tongue
What do the lips and cheeks consist of?
Orbicularis oris muscles, buccinator muscles
Vestibule
Oral Cavity - lies between teeth + gums
Labial frenulum - median attatchment of each to each gum
What does the palate consist of?
- Hard palate
- Soft Palate
State the function of the hard palate
Made from palatine bones + palatine processes from maxillae
It is corrugated which helps it created friction between tongue + pallate
State the function of the soft palate
Fold in palate, formed by skeletal muscle
- Closes nasalpharynx when swallowing
- Downward projection off soft palate - uvula
- Anchored by palatoglossal + palotopharyngeal arches
State the functions of the tongue
- Mixing of food when chewing
- Produces bolus
- Initiates swallowing, taste, speech
What are the intrinsic muscles of the tongue responsible for?
Change in shape of tongue
What are the extrinsic muscles of tongue responsible for?
Change in position of tongue
What is the lingual frenulum responsible for?
Medial attacthment between tongue and floor of mouth
What is ankyloglossia?
Fused tongue
Tied tongue
Short frenulum
How is ankyloglossia treated?
Surgery
What are the 4 digestive processes in the mouth?
Ingestion
Mechanical digestion (mastication)
Chemical digestion
Propulsion
Name a drug which can be absorbed through the oral mucosa
Nitroglycerine - used to alleviate angina pain
Describe the process of mastication
- Cheeks + lips closed. Holds the food between the teeth, the tongue mixes food with saliva to soften it
- Teeth cut + break down solid food
- Voluntary contractions of muscles that close the jaw
- Rythm / pattern of jaw movements controlled by stretch reflexes + responses to pressure inputs from receptors in cheeks, gums, tongue
State 4 functions of the Saliva
- Dissolve + moiston food
- Contains enzymes which start breakdown of starch
- Production of bolus
- Cleans mouth
How are chemoreceptors stimulated?
By acidic substances
How are mechanoreceptors stimulated?
By mechanical stimuli
Xerostomia
Strong sympathetic stimulation
Salivation inhibited
What are the 3 extrinsic salivary glands?
- Parotid
- Submandibular
- Sublingual
What are buccal salivary glands?
Intrinsic salivary glands
Scatted across oral mucosae
Keeps mouth moist
Describe the composition of saliva
Secreted by serous cells and mucous cells
99.5% water, slighly acidic:
- Electrolytes e.g. Na+
- Metabolic waste, urea
- Salivary amylase, lingual lipase
- Lysozymes, Defensins
- Mucin
What is the role of “friendly bacteria”?
Convert nitrates from food derived into nitric oxide
How can saliva be used in medicine?
Can detect conditions
Including oral cancer, diabetes
Can detect hormones
State two patholgies related to the salivary glands
- Mumps
- Sjogrens syndrome
Describe what causes Mumps
- Inflammation of parotid gland
- Caused by myxovirus
Easily transmited through saliva
Symptoms of Mumps
- Sterelity in males
What causes Sjogrens syndrome
- Autoimmune condition
Symptoms of Sjogrens syndrome
-Affects salivary + lacrimal glands
-Xerostomia
Function of intrinsic salivary glands
Continuosly keep mouth moist
Function of extrinsic salivary glands
Produce secretions when ingested food stimulates chemoreceptors and mechanorecptors in mouth
What increases salivation
Ingested food in mouth
Thought of food
Smell of food
Irritants in lower regions of GI tract
Sympathetic stimulation
What decreases / inhibits salivation
Dehydration
Extremely strong sympathetic stimulation
Describe the position of the oesophagus
Oesphagus runs through the thorax, from the pharnyx to the stomach
It joins onto the stomach via the cardiac orifice
It pierces the diaghragm at the oesophagul haitus
How does the oesphagus join to the stomach?
It joins onto the stomach via the cardiac orifice
How does the oesphagus join to the diaphragm?
It pierces the diaghragm at the oesophagul haitus
What are the different layers of the oesphagus?
- Mucosa
- Submucosa
- Adventitia
- Muscularis Externa
What type of epithelium is the mucosa made of?
Stratifed squammus epithelium
What is the function of the submucosa?
- Mucus secretion
- arealor connective tissue
What are the two layers of the muscularis externa?
- Longitudinal
- Circular
Describe the muscle composition of the muscularis externa
Proximal third = skeletal muscle
Middle - mix of skeletal + smooth
Inferior - smooth
What is the adventitia made of?
Fibrous connective tissue
Instead of serosa
What are the different types of epithelium
8 Different types:
- Simple squamous
- Stratified squamous
- Simple cuboidal
- Stratified cuboidal
- Simple columnar
- Pseudostratified columnar
- Stratifed comumnar
- Transitional
State the function and location of simple squamous epithelium
Lungs, lymphatic vessels, blood vessels
Diffusion, filtration, lubrication
State the function and location of stratified squamous epithelium
Oesophagus, mouth, vagina
Protection against abrasion
State the function and location of simple cuboidal epithelium
ducts, secretory regions of small glands, kidney tubules
section + absorpiton
State the function and location of stratified cuboidal epithelium
Secretory glands (salivary, sweat)
Protection
State the function and location of simple columnar epithelium
Cilliated tissue, found in bronchi
Non-cilliated in digestive tract
Secretion (mucus + enzymes), absorption
State the function and location of pseudostratified columnar epithelium
Cilliated tissue, trachea
Secrete mucus
State the function and location of stratified columnar epithelium
Urethra
Protection
Compare and contract the adventitia and the serosa
The adventitia is made of dense fibrous connective tissue. The serosa is made of connective tissue surrounded by mesothelium (provides friction)
The adventitia is retroperitoneal, and serosa is intraperitoneal
Adventitia is found in mouth, pharynx, oesophagus, pylorus of stomach, distal duodenum, ascending colon, descending colon, anal canal
Serosa is found in most of stomach, duodenum, caecum, sigmoidal canal, transverse canal, rectum
Describe the function of the pharynx
Allows passage for fluid, food, air
Pharyngeal constrictor muscle contracts, propels food into oesophagus
Type of epithelium in pharynx
Stratified squamous epithelium
Describe the structure of the pharynx
Allows passage for food, fluid, air
Histology similar to oral cavity
Stratified squamous epithelium
2 layers of skeletal muscle:
inner layer: longitudinal musckle
outer layer: pharyngeal contrictor muscle
What is deglutition
Chewing
What is the “boccal phase” of deglutition?
Voluntary contractions of the tongue
What is the “pharyngeal-oesophagal phase” of deglutition?
Involuntary contractions of the tongue
Which parts of the upper GI system does deglutition involve?
Pharynx
Oesophagas
Soft Palate
Tongue
22 muscle groups
Describe the 4 stages of deglutition
1.Upper oesophagal sphincter contracted - closed.
2. BOCCAL PHASE: Tongue touches hard palate, this forces food bolus into oropharynx
3. Involunary phase / pharyngeal-oesophagal phase, larynx + uvula rise to prevent food bolus from entering respiaratory passageways, tongue blocks off mouth, upper oesophagal sphincter relaxes, therefore, opens, food bolus can enter
4. Outer pharyngeal constrictor muscles contract, propels food bolus into oesophagas
5. Food bolus moves from oesophagas to stomach via peristalsis
6. Gastroesophagal sphincter relaxes, opens, food enters stomach
What causes hitaus hernia?
- Abonormal location of oesophagogastric junction
- This leads to gastric cardia above diaphragm
THIS CAN BE CAUSED BY OBESITY
What does hitaus hernia lead do?
Weakened diaphragm, increased intra-abdomenal pressure
Acid reflux
Describe the anatomy of the stomach
Refer to diagram L3
- Cardia - surrounds cardiac orifice
- Fundus - bulges over cardia, dome shaped below diaghragm
- Body - midportion
PYLORIC REGION
pylorus - gate keeper
funnel shaped
pyloric sphincter - Greater curvature - Convex lateral surface, contain ruggae, longitudinal folds
- Lesser curvature - concave medial surface
What is the function of the stomach?
Turns food bolus into chyme
What are omenta?
Omenta are mesenteries which arise from the curvatures of the stomach
They “tether” the stomach to body wall and other body organs
State the two types of omenta and describe their structure and positioning
Lesser omenta - from liver to lesser curvature
Greater omenta - drapes from greater curvature
contains fatty deposits
Which 2 vessels are involved in the blood supply of stomach?
Celiac trunk
Veins of hepatic portal system
What is the sympathetic ANS supply of stomach?
- Splanchnic nerve
- Celiac PLEXUS
What is the parasympathetic ANS supply of stomach?
Vagus nerve
What happens during physical digestion in the stomach?
Denaturation of proteins
By enzymatic digestion of proteins by enzyme pepsin (or renin in infants)
Stomach secretes Intrinsic factor required in absorption of vitamin B12 - lack of intrinsic factor, lack of absoprtion of b12, pernicous anemia
Physical digestion delivers chyme to small intestine
Describe the tissue structure of the stomach wall
Diagram L3
Mucosa
Submucosa
Muscularis externa
Serosa
Lumen
Production of gastric juice
- Mucus produces gel like substance which protects mucosa from gastric juice
-Mucus traps bicarbonate rich fluid beneath it
-This produces Smooth lining of mucosae has deep gastric pits which develop tubular gastric glands which secrete gastric juice
-Gastric juice contains pepsionogens (chief cells) and HCl (parietal cells)
-Stomach produces 2.5L gastric juice
pH in lumen of stomach wall
1-2
pH above mucosa in stomach wall
6-7
Describe the mucosa of the stomach
Simple columnar epithelium, composed of mucous cells
These mucous cells produce a cloudy, protective double layer of alkaline mucus. The outer layer / surface layer is viscous insoluble mucus which traps a layer of bicarbonate-rich fluid underneath
The inner layer is a smooth lining consisting of many gastric pits which lead to gastric glands which produce gastric juice
State the function of mucous neck cells
Help produce double layer of mucus in the stomach mucosa
What is the mucosal barrier and how is it formed?
Portective layer of bicarbonate-rich mucous
Formed by tight junctions between epithelial cells
(surface mucous cells produce HCO3- and mucus, mucous neck cells produce mucus, this combines to form bicarbonate rich mucus which forms the mucosal barrier, pH 7)
Why does the stomach renew its surface epithelium often (every 3-6 days) ?
Epithelial cells which are damaged are quickly replaced by dividing stem cells
(Stem cells divide to form daughter cells which can specialise into epithelial cells)
State 2 glandular cells found in the gastric glands and state their functions
Parietal cells - secrete HCl - digestion, disinfectant
Chief cells - secrete pepsinogen - produces pepsin - protein digestion
