GI Anatomy Flashcards
What are the three types of innervation to the tongue?
What are the four extrinsic muscles and four intrinsic muscles of the tongue?
Extrinsic Muscles: Palatoglossus, Styloglossus, Hyoglossus, Genioglossus.
Intrinsic Muscles: Transverse, Superior longitudinal, Inferior longitudinal, Vertical.
Explain the motor innervation of the tongue.
Vagus nerve - Innervates the palatoglossus muscle.
Hypoglossal nerve - innervates all 7 other muscles of the tongue.
What papilla are central to the tongue?
Filiform papillae - do not taste.
Why do the oral and pharyngeal parts of the tongue have different innervation?
Oral and pharyngeal parts have different innervation because they arise from different pharyngeal arches.
Oral part = anterior 2/3 before terminal sulcus.
Pharyngeal part = posterior 1/3 after terminal sulcus.
What nerve provides general sensation to the tongue?
- what is this a branch of?
Lingual nerve
- a branch of the Mandibular nerve CN V3
What nerves provides taste sensation to the tongue?
- what is this a branch of?
Chorda tympani
- Branch of the facial nerve CN VII
What nerve gives both taste sensation and general sensation to the posterior pharyngeal part of the tongue?
Glossopharyngeal nerve.
What are the major salivary glands?
Parotid
Submandibular
Sublingual
Where are the minor salivary glands found?
Throughout the oral mucosa.
Para-otid
Para-otid = next to ear
Explain the secretomotor nerve supply to the parotid gland.
• Originates in glossopharyngeal nerve - synapses in otic ganglion. Then carried to gland in auriculotemporal nerve.
Explain the secretomotor nerve supply to the submandibular gland.
Innervation from chorda tympani (cn. VII) - carried in lingual nerve.
Explain the secretomotor nerve supply to the sublingual gland.
Innervation from chorda tympani (cn. VII) - carried in lingual nerve.
Is the innervation to the salivary glands sympathetic or parasympathetic?
Parasympathetic - as not under conscious control.
Summary of innervation to the salivary glands:
What nerve passes through the parotid gland but does not supply it?
- Important in a parotidectomy.
Facial nerve
What are the muscles of mastication?
Temporalis
Lateral pterygoid
Medial pterygoid
Masseter
How does the temporalis move the mandible?
Anterior fibres elevate the mandible.
Posterior fibres retract the mandible.
How does the masseter move the mandible?
Elevates the mandible.
How does the medial pterygoid move the mandible?
Elevates the mandible
How do the laterl pterygoids move the mandible?
NETTERS
What are the functions of the small intestine?
Mechanical and chemical digestion.
Absorption of 90% of nutrients.
What are the functions of the large intestine?
Reabsorption of water and electrolytes.
Conversion of indigestible food into faeces.
What are the plicae circulares, and what is their function?
Plicae circulares are the perpendicular circular folds of the small intestine.
- they increase surface area of the small intestine and slow chyme flow.
What cells make up the intestinal glands (aka crypts of Lieberkuhn) of the small intestine?
- Enterocytes, Goblet cells, Paneth cells, etc. and multipotent stem cells to replace eroded epithelia.
- Produce intestinal juices rich in digestive enzymes and hormones.
What are lacteals of the small intestine?
A lacteal is a lymphatic capillary that absorbs dietary fats in the villi of the small intestine.
How does the histology of the largeintestine differ from that of the small intestine?
No circular folds or villi.
Many more intestinal glands which are deeper.
What is the function of enterocytes?
Absoptive cells with a microvilli border.
What is the function of goblet cells of the intestinal glands?
Secrete mucous to help faciliate faecal movement.
Hirschsprung’s disease
A disorder of the enteric nervous system. Hirschsprung’s disease involves agangliosis of both plexuses in the distal colon and rectum.
Leads to poo becoming stuck in the bowels.
How does Hirschsprung’s disease present?
Functional obstruction develops from spasms in the denervated colon.
Presents as severe constipation in the first 2 months.
What is the radiographic appearance of Hirschsprung’s disease?
Colonic distension.
Aganglionosis
The total absence of ganglion cells.
Meckel’s diverticulum
Meckel’s diverticulum is an outpouching or bulge in the lower part of the small intestine. The bulge is congenital (present at birth) and is a leftover of the umbilical cord.
- persistence of the vitellointestinal duct.
What are the symptoms of Meckel’s diverticulum?
Gastrointestinal bleeding (which can be seen in the stool).
Abdominal pain and cramping.
Tenderness near the navel (belly button).
Obstruction of the bowels, a blockage that keeps the contents of the intestines from passing.
What are complications of Meckel’s diverticulum?
Can lead to ulceration and cause gastric bleeding.
Omphalocele
A birth defect of the abdominal (belly) wall. The infant’s intestines, liver, or other organs stick outside of the belly through the belly button.
How is omphalocele treated?
Surgery.
Treat with antibiotic cream and wait for the skin to grow over the membrane (called “paint and wait”)
Gastroschisis
Gastroschisis is a birth defect of the abdominal (belly) wall. The baby’s intestines are found outside of the baby’s body, exiting through a para-umbilical defect in the abdominal wall.
How is gastroschisis diagnosed?
Antenatal US can show herniation to right of umbilicus, freefloating and small fetal abdominal circumference.
What is the difference between omphalocele and gastroschisis?
In omphalocele the herniated intestines are covered by a peritoneal membrane and amnion.
In gastroschisis the there is no surrounding membrane for the herniated bowel.
Meckel’s diverticulum
Meckel’s diverticulum is a congenital outpouching or bulge in the lower part of the small intestine.
- remnant of the vitelline duct.
- inflammation leads to Meckel’s diverticulitis
What is the main risk factor for diverticulitis?
Low fibre diet for an extended period of time.
Where does diverticulitis most commonly occur?
Sigmoid colon
Crohn’s disease affects where most severely in the small intestine?
Terminal ileum - causing terminal ileitis.
What is the effect of Crohn’s causing terminal ileitis?
Inflammation of the terminal ileum results in vitamin B12 not being asorbed. This can lead to vitamin B12 deficiency which can cause pernicious anaemia.
What is the lesser sac?
The lesser sac, also known as the omental bursa, is the cavity in the abdomen that is formed by the lesser and greater omentum.
Viteline duct
The vitelline duct acts as a communicating tract between the embryonic yolk sac and its primitive midgut during early human development.
In the case of an abdominal bleed, why should you avoid lying in the supin position?
When lying in the supine position blood pools into the perirenal and pararenal recesses (these are large spaces that can hold a large volume of blood).
Sitting upright causes blood to pool in the rectovesival and uterine pouches which absorb blood more slowly.
Blood supply to:
Midgut
Hindgut
Midgut = SMA
Hindgut = IMA
Sigmoid volvulus
Twisting of the sigmoid colon which leads to obstruction of blood supply.
What sign is seen on X-ray in a case of sigmoid volvulus?
Coffee bean sign
Anal fistula
An anal fistula is a small tunnel that develops between the end of the bowel and the skin near the anus (where poo leaves the body). They’re usually the result of an infection near the anus causing a collection of pus (abscess) in the nearby tissue. When the pus drains away, it can leave a small channel behind.
Where are the crypts of lieberkuhn found and what is their function?
Found in the small intestine.
Contain immune cells for defence.
Imperforate anus
Imperforate anus is a congenital defect in which the opening to the anus is missing or blocked.
Embryology
