3: Development of Gut / Salivation and Swallowing Flashcards
What does the folding in week 4 and 5 create? (3 things)
- Primitive Gut
- Abdominal Wall
- Coleomic Cavity
What does the lateral folding do?
Makes primitive gut become tubular
What are the 3 regions of the primitive gut?
- Foregut
- Midgut
- Hindut

What surrounds the gut?
Mesoderm
What does the mesoderm split into?
- Somatic MEsoderm
- Splanchninc Mesoderm

What does the somatic mesoderm develop into?
Muscle and fasciae of abdominal wall
What does the splanchnic mesoderm develop into?
SM of gut wall
What is the space created by the mesoderm split caled?
Coleomic cavity (intraembryonic cavity)

What is the coleomic cavity the forerunner of?
Pleural and peritoneal cavities
What does the coleomic cavity surround?
Gut cavity

What does the rotation of the mid-gut loop establish?
Disposition of abdominal viscera (internal organs)

What does the first rotation of the midgut loop do?
Lengthens small and large intestines
What does the second rotation of the midgut loop do? (2 things)
- Puts small and large intestines in position
- Gives mesentry of small intestine its twisted appearance
When and where does the hindgut end?
At cloaca
Week 6
What happens after the hindgut ends at the cloaca?
Cloaca undergoes anteroposterior division
Wedge of mesoderm fold (urorectal fold) grows down and splits cloaca:
- Anteriorly: Urogenital Sinus + Urethra
- Posteriorly: Anorectal Canal

Where is the superior part of the anal canal derived from?
Hindgut
Where is the inferior part of the anal canal derived from?
Endoderm
Where do the superior and inferior parts of the anal canal meet?
Pectinate line

What is the Vitelline Duct?
Tube that connects yolk sac to midgut lumen
Supposed to obliterate but can persist → causes problems
What are the problems that occur if the Vitelline Duct persists? (3 things)
- Meckel’s Divericulum
- Vitelline Cyst
- Vitelline Fistula

What is Meckel’s Diverticulum? (3 points)
- Vitelline duct bulges out from small intestine
- Contains ectopic gastric / pancreatic tissue
- Ectopic tissue secrets enzymes and acids into tissue → ulceration

What is Vitelline Cyst?
Duct forms fibrous strand (of ligaments) on either end

What is Vitelline Fistula?
Direct communication between umbilicus and intestinal tract → faecal matter comes out of umbilicus (belly button)
FFFFFistula iffffeeeee khara leaking out

What happens to the primitive gut if cell growth of some structures is so rapid?
Lumen of primitive gut is obliterated
What restores the obliteration of the primitive gut lumen?
Recanalisation
What is recanalisation?
Restoration of the lumen of the primitive gut
What occurs if recanalisation of the primitive gut lumen is unsuccesful? (2 things)
- Aterisa: complete loss of lumen
- Stenosis: narrowing of lumen

What is pyloric stenosis?
Narrowing of the exit of the stomach
What is pyloric stenosis caused by?
Hypertrophy of circular muscle in pyloric sphincter region
What are some abdominal wall defects? (2 things)
- Gastroschisis
- Omphalacoele
What is Gastroschisis?
Failure to close abdominal wall at embryo folding
→ Gut tube and its derivatives outside body

What is Omphalacoele?
Part of the gut remains outside of abdominal cavity through the belly button
But still covered by thin amnion layer

What are some hindgut abnormalities? (3 things)
- Imperforate Anus (D)
- Anal / Anorectal Agenesis (B)
- Hindgut Fistulae (A)

Wha is Imperforate Anus?
Failure of anal membrane to rupture
D in picture

What is Anal / Anorectal Agenesis?
No development of anus / rectum
B in picture

What is Hindgut Fistulae?
Abnormal connection within the hindgut
A in picture

What are the functions of saliva? (3 things)
- Lubricates + wets food
- Starts digestion of carbs (amylase)
- Protects oral environment
What type of gland are salivary glands?
Ducted exocrine glands
What are the salivary exocrine glands made up of?
- Acini (lined with acinar cells)
connected via:
- Duct cells

What are the 3 pairs of salivary glands?
- Parotid glands (25%)
- Sublingual glands (5%)
- Submaxilary glands (70%
What is the saliva of the Parotid glands like?
Serous saliva
Water secretion:
- Lots of enzymes
- Little mucus
Subway is a green logo so beh mucus, but parrot’s don’t have bogies
What is the saliva of the Sublingual glands like?
Mucus saliva
Viscous secretion:
- No enzymes
- Lots of mucus
Subway is a green logo so beh mucus, but parrot’s don’t have bogies
What is the saliva of the Submaxillary glands like?
Mixed serous and mucus saliva
Serous + mucus acini
Best of both worlds living life to da MAX
What is the chemical property of saliva?
Hypotonic
What is the general serous saliva secretion mechanism?
- Acinar cells secrete isotonic fluid with enzymes
- Duct cells then remove Na+ and Cl-, and add HCO3-
What is the in-depth serous salivary secretion mechanism?
- Acinar cells actively secrete Cl- into duct lumen
* Water + Na+ follow - Na/K-ATPase Antiporter lowers Na+ concentration inside Duct Cell
- This causes Na+ to diffuse from Duct Lumen → Duct Cell
- Na/K-ATPase Antiporter increases K+ concentration inside Duct Cell
- This causes Cl- to be expelled via K/Cl-Symporter
* This lowers Cl- concentration in Duct Cell - This causes Cl- to diffuse from Duct Lumen → Duct Cell via Cl/HCO3-Antiporter
- HCO3- goes other way via Cl/HCO3-Antiporter

What nervous system controls salivary secretion?
Autonomic (PS NS & SNS)
What does the Parasympathetic NS do in salivary secretion? (2 things)
- Increases Primary secretion (acinar cells)
- Increases HCO3- secretion (duct cells)
Which nerves supply parasympathetic innervation to the Parotid gland (for salivation)? (2 things)
- Glossopharyngeal N. (CN 9)
- Otic ganglion
What does the Sympathetic NS do to salivary secretion?
Reduces blood flow to glands → reduces salivary flow → dry mouth
What nerves supply sympathetic innervation to the Parotid gland? (1 thing)
Superior Cervical Ganglion
Where does the oesophagus extend from and to?
Pharynx → Stomach
What are the 3 layers of the oesophagus?
- Mucosa
- Submucosa
- Muscularis Externae

What is the layers of the oesophagus mucosa? (3 things)
- Non-Keratinised Stratified Squamous
- Lamina Propria
- Muscularis Mucosa (MM)

What can be foud in the Submucosa of the oesophagus?
Mucus secreting glands
What is the difference between the upper and lower oesphogeal Muscularis Externae?
In upper 1/3 of oesophagus, the ME is:
- Striated (skeletal) muscle →for conscious swallowing
- Somatic (voluntary) control
In lower 2/3 of oesophagus, the ME is:
- Smooth muscle under autonomic control (peristalsis)
- PNS control
What are the 3 phases of swallowing?
- Voluntary Phase
- Pharyngeal Phase
- Oesophageal Phase
What happens in the Voluntary Phase of swallowing?
Tongue moves bolus back onto the pharynx
What happens in the Pharyngeal Phase of swallowing?
Afferent information from pressure receptors in Palate & Anterior Pharynx → Swallowing Centre in Brainstem → triggers set of movements
What set of movements are triggered by the Swallowing Centre in Brainstem? (4 things)
- Breathing inhibition
- Raising of larynx
- Glottis closure
- Upper oesophageal “sphincter” opens
What happens in the Oesophageal Phase of swallowing? (2 things)
- Peristalsis propels bolus into stomach
* Coordinated by extrinsic nerves from Swallowing Centre in Brainstem - Lower Oesophageal “sphincter” opens
What are some swallowing disorders? (2 things)
- Dysphagia (difficulty swallowing)
- Odynophagia (pain when swallowing)
What are the causes of Dysphagia? (2 things)
- Primary oesophageal disorder
* e.g motility problems of smooth muscle → NO peristalsis (achalasia) - Secondary oesophageal disorder
* e.g obstruction / compression of oesophagus because tumour
What are the 2 types of Dysphagia?
- Oesophageal Dysphagia (for solids)
- Oropharyngeal Dysphagia (for liquids)
How do you investigate Oesophageal dysphagia?
With barium swallow / endoscopy
How do you investigate Oropharyngeal dysphagia?
With flexible endoscopy evaluation of swallowing
How is gastro-oesophageal reflux prevented by the body? (3 things)
- Lower oesophageal “sphincter” (one way valve)
* Stops stomach contents refluxing into oesophagus - Angle of His (at same point of “sphincter”)
- Crus of diaphragm (helps with sphincter activation)

What are the consequences of gastro-oesophageal reflux?
Barret’s oesophagus
- Abnormal changes of epithelial cells of oesophagus
- Non K Stratified Squam – Metaphasia →Columnar / Goblet Cells
What is Barrets oesophagus associated with?
Adenocarcinoma
What are the symptoms of Gastro-oesophageal reflux disease? (3 things)
- Cough
- Hoarseness
- Asthma