Gastrointestinal Anatomy Flashcards by Hettie Stevens

Mouth boundaries

From lips to palatoglossal arches, cheeks form walls
Floor is mylohyoid muscle

Oral cavity is teeth to oropharynx
Vestibule is between teeth and lips

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Teeth

Made of dentine (pulp cavity containing nerves and vessels)
Crown covered in enamel
Anchored in sockets by periodontal ligament

Teeth and gums (gingivae) - superior and inferior alveolar nerves and vessels - from maxillary division at top, mandibular at bottom

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Numbers of teeth per quadrant

Decididuous (milk) - 2 incisors, 1 canine, no premolar, 2 molar
Adult - 2 incisors, 1 canine, 2 premolar, 3 molar

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Tongue

Made of muscles - intrinsic change shape, extrinsic move tongue
Root is anchored to mandible and hyoid bone
Stratified keratinised squamous epithelia
Covered in papillae - taste buds
Vallate papillae divide body from root of tongue

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Nerve supply to tongue

All motor - hypoglossal nerve
Posterior 1/3 - sensation and taste from glossopharyngeal
Anterior 2/3 - sensation - mandibular, taste - facial

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Looking into mouth

Palatoglossal arch in front
Then palatine tonsils
Palatopharyngeal arch

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Muscles of mastication

Temporalis and massete - superficial
Medial and lateral pterygoid - deep
- supplied by mandibular branch of trigeminal

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Deglutition

= swallowing

1) VOLUNTARY
- bolus to dorsum of tongue
- up against hard palate as mylohyoid contracts
- bolus to pharynx
- styloglossi and palatoglossi raise posterior part of tongue
2) INVOLUNTARY
- soft palate elevates, sealing off nasopharynx
- long pharyngeal muscles pull larynx upwards
- laryngeal orifice closed by aryepiglottic and oblique arytenoids
- pharyngeal constrictors constrict in sequence
- cricopharyngeus relaxes
3) INVOLUNTARY
- wave of peristalsis moves bolus down oesophagus

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Palate

Hard palate - palatal processes of maxillae and horizontal plates of palatine bones
Soft palate - 5 muscles - tensor and levator veli palatine, palatoglossus, palatopharyngeus, uvular

Maxillary artery supplies
Sensory - maxillary division of trigeminal
Motor - mainly from pharyngeal plexus

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Muscles of pharynx

External - constrictors
Internal - palatopharyngeus, salpingopharyngeus (by opening of eustachian tube in nasal cavity), stylopharyngeus (from back of ear)

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Suprahyoid muscles

Geniohyoid - to chin
Mylohyoid - under tongue, floor of mouth
Digastric - mentum to hyoid to mastoid process
Stylohyoid - to bottom of chin

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Infrahyoid muscles

Sternohyoid - to sternum
Omohyoid - to scapula
Thyrohyoid
Sternothyroid

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Parotid salivary gland

Duct pierces buccinator (cheek), enters oral cavity opposite 2nd maxillary molar tooth
Glossopharyngeal nerve innervates
Running through - facial nerve, external carotid, superficial temporal and maxillary artery, retromandibular vein

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Submandibular salivary gland

Duct opens adjacent to lingual frenulum under tongue

Facial nerve innervates

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Sublingual salivary gland

Numerous small ducts open into floor of mouth along sublingual folds
Facial nerve innervates

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Oesophagus

Starts at C6 (cricoid cartilage level), 25cm long
Mucosa stratified squamous epithelium
No serosal layer
Outer longitudinal and inner circular fibres

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Four main constrictions of oesophagus

1) At C5, cricopharyngeal sphincter
2) At aortic arch
3) At left main bronchus
4) Cardiac sphincter, gastro-oesophageal junction

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Arterial supply of oesophagus (and lymph)

Upper third - inferior thyroid artery
Middle - branch of thoracic aorta
Bottom third - left gastric artery

Lymph drains to posterior mediastinal nodes, left gastric nodes

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Stomach

Longitudinal, oblique and circular muscle fibres
Columnar epithelium
Intraperitoneal

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Nervous supply to stomach

Intrinsic - enteric NS - coordinates contractions and secretions
Extrinsic - autonomic - modify activity (parasymp increases)

Parasympathetic - anterior and posterior vagal trunks
Sympathetic - sympathetic trunks via coeliac plexus

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Blood and lymph supply to stomach

Veins drain to portal system
Lymph to coeliac nodes

Splenic artery behind stomach to spleen
Gastroepiploic arteries run below to stomach and spleen

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Lesser omentum

Two layers of peritoneum extending between liver and lesser curvature of stomach

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Lesser sac

Between lesser and greater omentum
Subsection of peritoneal cavity, posterior to lesser omentum and stomach, anterior to retroperitoneal organs of posterior abdominal wall

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Greater omentum

Two layers of peritoneum laying together -> 4 layers
Between greater curvature of stomach and transverse colon
Hangs like apron over intestines
Contains adipose tissue

Omental foramen is communication between lesser and greater omentum

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Endoscopy

OGD = oesophagogastroduodenoscopy
- lie on left side, swallow tube
TOE = transoesophageal echocardiography
- ultrasound probe through oesophagus to view heart

Indicated after upper GI bleed, foreign body, gastric cancer, GORD

Oesophagus histology

Stratified squamous epithelia, to protect from acid reflux
Peristalsis mediated by muscularis externa
Submucosal glands, especially in lower oesophagus

Epithelia
Lamina propria - not much, mainly gastric glands
Muscularis mucosa
Submucosa
Circular muscle
Longitudinal muscle
(NO Serosa)

Gastro-oesophageal sphincter

LES has no marked thickening of circular muscle, so physiological NOT anatomical sphincter

Stomach cell types

PARIETAL - dominant cell type, large cells with bright pink cytoplasm and central dark nucleus
CHIEF - light grey cytoplasm, nucleus at base of cell, abundant in gastric glands
ENDOCRINE - light grey cytoplasm (look very similar to chief), but less abundant
MUCOUS NECK - empty spaces in surface epithelium, found at bottom of gastric pits and scattered
SURFACE EPITHELIAL - dominant type lining gastric pits, columnar epithelial, nucleus at base

Histology of duodenum

Abundant tall villi separated by crypts
Brunner’s glands (submucosal)
Paneth cells found here in crypts - prominent apical eosinophilic granules, for host defence as secrete anti-microbial factors

Ileum histology

Abundant smaller villi separated by crypts

Peyer’s patches (lymph) pack mucosa, covered by flattened epithelium with less obvious villi

Large intestine histology

No villi, just crypts
Mucosa has crypts filled with mucus-secreting goblet cells
Loose connective tissue forms submucosa
Crypts of Lieberkuhn - crypts packed with mucus-secreting goblet cells, for salt and water secretion

Duodenum

In epigastric region
1st part at L1, intraperitoneal
Rest is retroperitoneal as forms C shape around pancreas
Simple columnar epithelium with villi and circular folds (pilicae circulares)

Secretion stimulated by secretin - local hormone, and vagus nerve
Dual blood supply and lymph drainage - 1st 1/3rd is foregut (coeliac), then midgut (superior mesenteric). Major duodenal papilla marks change

Pancreas

In epigastric region
Retroperitoneal, but tip of tail intraperitoneal
Duct opens at major duodenal papilla
Endo and exocrine gland

Secretion stimulated by cholecystokinin and vagus nerve

Blood supply to pancreas

Splenic artery runs along top of body
Superior and inferior pancreaticoduodenal arteries run around head

Corresponding veins drain to portal system - splenic vein biggest, posterior

Spleen

Red and white pulp
For removal of old RBCs from blood, largest lymphoid organ
Sits under 9th-11th ribs on left - left hypochondriac region
Intraperitoneal
Splenic artery and vein supply

Superior/anterior - stomach
Inferior - left colic flexure, left kidney

DELICATE and vulnerable to injury - if rupture by blunt trauma, significant bleeding, left flank pain

Foregut surface anatomy

Liver - deep to ribs 5-11 on right, crosses midline
Gallbladder - behind tip of 9th costal margin
Pancreas - neck overlies L1-2, body and tail left and superior
Spleen - 9-11th ribs on left (only palpable at 3x normal size)

Referred pain by region

Foregut -> epigastric
Midgut -> umbilical
Hindgut -> hypogastric

Retroperitoneal refer to back

Liver

Largest gland in body - 1.5kg in adult
Right hypochondriac region, extending to epigastric
Intraperitoneal, covered in visceral peritoneum apart from bare area where joins to diaphragm
Right, left, caudate (top) and quadrate (bottom) lobes
Falciform ligament across front, attaches to abdominal wall at front and diaphragm above
Lymph to coeliac nodes

Porta

In porta hepatis, fissure
Carries hepatic portal vein (80% blood to liver), L + R hepatic arteries, bile duct

Hepatic portal vein - SMV (midgut), IMV (hindgut) and splenic vein (foregut) all feed in

Functions of liver

METABOLIC - fats, proteins, carbs
PRODUCTION - bile, plasma proteins, albumin, clotting factors, urea
STORAGE - glycogen, vitamins, minerals
IMMUNITY - produce immune factors and remove bacteria
HOMEOSTASIS - regulates glycogen release in response to glucagon or insulin from pancreas, produces heat for body temperature control

Embryological remnants in liver

Ligamentum teres (round at bottom of falciform) - old umbilical vein 
Ligamentum venosum (between left and caudate lobes) - old ductus venosus, shunt

Gallbladder

In right hypochondriac region
Intraperitoneal
Arterial supply from branch of right hepatic artery

To store and concentrate bile made by liver
Secretion stimulated by cholecystokinin, into duodenum

Biliary tree

Left and right hepatic ducts
Common hepatic duct
+ cystic duct from gall bladder
-> common bile duct

Gallstones

Form from bile pigments, cholesterol crystals so don’t show up on X rays
If dislodge -> pain and jaundice

Cholecystitis = acute inflammation
Biliary colic = cystic duct blocked, pain but no jaundice

Laporascopic cholescystectomy

= Lap chole

Scope in port superior to umbilicus
Inflate abdominal cavity with CO₂ to create space
Insert other ports
Isolate cystic duct and cystic artery
Make small cut, insert contrast, choleangiogram
Cut and clip cystic duct and artery
Cut through fat and fascia attached to posterior wall to liver
Insert bag, put gallbladder in
Saline solution into cavity to ensure no bleeding

Arcuate line

Half way between umbilicus and pubic symphysis

No posterior rectus sheath below

Inguinal canal

From ASIS to pubic tubercle

Anterior - skin, superficial fascia, external oblique aponeurosis
Posterior - medial - conjoint tendon (where transverse abdominus and internal oblique fuse at pubic tubercle)
- lateral - transversalis fascia
Roof - lower edge of internal oblique and transverse abdominus
Floor - inguinal ligament

Inguinal ring

Deep - opening in transversalis fascia lateral to lateral to pubic tubercle
Superficial - above and lateral to pubic tubercle

Contains spermatic cord and inferior epigastric vessels to testes in men
Or round ligament of uterus to anchor to abdominal wall in women

Below midinguinal ligament - femoral nerve
Below midinguinal point - femoral artery

Acute appendicitis

Interpreted as midgut pain as refers to umbilical region initially - as inflammation just in viceral peritoneum and appendix wall
As develops, pain localises to right iliac fossa
McBurney incision to remove

Hernias

The protrusion of tissue or an organ from the confines of its normal cavity to outside of that cavity
Inguinal hernia - above inguinal ligament
Femoral hernia - below inguinal ligament to exit abdominal cavity

Blood and lymph to small intestines

Blood supply from jejunal and ileal branches of superior mesenteric artery
Corresponding veins drain to portal system
Lymph drains along arteries to superior mesenteric lymph nodes

Features of jejunum

Larger, densely packed circular folds, larger villi
Deep red
Thicker mucosal wall
Few Peyer’s patches (lymphoid tissue)
More vascular - longer vasa recta, less arcades
Less fat in mesentery
Upper left quadrant, umbilical region
Intraperitoneal
Mesentery attaches to left of aorta to posterior abdominal wall

Features of ileum

Smaller, fewer, sparser circular folds
Pale pink
Thinner mucosal wall
Many Peyer's patches (lymphoid tissue)
Less vascular - shorter vasa recta, more arcades
More fat in mesentery
Lower right quadrant, hypogastric region
Intraperitoneal
Mesentery attaches to right of aorta to posterior abdominal wall

terminal ileum is site for absorption of vitamin B12 with intrinsic factor from stomach

Location of branching of aorta

Passes into abdomen at T12
Coeliac trunk arises at L1 (high)
SMA arises at L1 (low)
Renal arteries arise at L2
IMA arises at L3
Bifurcation to form common iliac arteries at L4

Structure and function of large intestine

Principle function to absorb water
Venous drainage via SMV and IMV to portal vein
Ileocaecal valve prevents reflux from caecum to ileum

Ascending and descending colon - retroperitoneal
Transverse and sigmoid colon - intraperitoneal

Taeni coli

Thickened bands of muscle in large intestine, don’t go complete width of colon
Gives sacculated appearance

Free taeni coli - ascending colon
Omental taeni coli - transverse colon
Mesocolic taeni coli - descending colon

Rectum

Dilatable holding area in pelvis, above levator ani
Upper part - superior rectal artery from IMA, lymph to inferior mesenteric nodes
Lower part - middle rectal artery from internal iliac, lumph to internal iliac nodes

Anal canal is 4cm long tube, from anorectal ring to anus

Upper anal canal

Above pectinate line
Derived from endoderm
Simple columnar epithelium
Stretch sensors - inferior hypogastric plexuses
Superior rectal artery from IMA supplies
Superior rectal vein to IMV drains
Lymph to internal iliac nodes

Lower anal canal

Below pectinate line
Derived from ectoderm
Stratified squamous epithelium
Pain, temperature, pressure receptors - inferior rectal nerve
Inferior rectal artery supplies
Inferior rectal vein drains
Lymph to superficial inguinal group nodes

Anal pathology

Weakness in levator ani muscles -> incontinence or prolapse of rectum (and uterus in women)
Infection may seed next to anal canal at ischioanal fossa -> abscess formation
Potential portosystemic anastamoses site as dual system of blood drainage

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Gastrointestinal Anatomy Flashcards

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