S3) Anatomy of the Abdomen Flashcards
State the structure and functions of the mucosal epithelial layer
- Structure: selectively permeable barrier
- Function: promote absorption, produce hormones and mucus, facilitate transport and digestion of food
State the structure and function of the mucosal lamina propria
- Structure: lots of lymphoid nodules and macrophages
- Function: produce antibodies (mainly IgA)
State the structure and functions of the muscularis mucosae
- Structure: layers of smooth muscle orientated in different directions
- Function:
I. Keeps epithelium in contact with gut contents
II. Keeps crypt contents dynamic
Describe the structure of the submucosa of the gut
- Contains dense connective tissue, blood vessels, glands, lymphoid tissue
- Contains submucosal plexus (Meissner’s)
Describe the contents of the inner circular muscle layer
Contains myenteric (Auerbach’s) plexus
Describe the structure of the serosa in the gut
- Continuous with mesenteries
- Contains blood and lymph vessels and adipose tissue
What kind of epithelia is found in the gut?
- Stratified squamous (oesophagus and distal anus)
- Simple columnar (everything else)
What is an enterocyte?
An enterocyte is a simple columnar epithelial cell that absorbs nutrients
The enterocyte is the most predominant cell in the small intestine and lumen.
Describe it structure
- Consists of apical and basolateral membranes
- Blood vessels/lymphatics lie immediately below cell
How are enterocytes adapted for their absorbative function?
Microvilli (collectively termed brush border)
Where are goblet cells found?
- Scattered in between enterocytes
- Increase in number from duodenum to colon
Describe the structure of the goblet cell
- Narrow base (mucus compresses nucleus to its base)
- Larger apical size
Goblet cells secrete mucus.
What are the three main functions of mucus?
Protects epithelia from:
- Friction (acts as lubricant)
- Chemical damage (acidic environment)
- Bacterial inflammation (forms physical barrier)
Where are gastric surface mucous cells found?
Gastric surface mucous cells line gastric mucosa/gastric pits
What do gastric surface mucous cells do?
Secrete mucus/HCO3 that forms barrier to stomach acid
How is the gut tube adapted for the increased surface area required for absorption?
- Permanent folds
- Villi
- Microvilli
Why does the stomach form temporary folds?
- The stomach needs to be easily expandable
- Temporary folds form called rugae
Crypts are found in the small intestine and colon.
What type of cells do they contain?
Contain specialised cells:
- Stem cells
- Paneth cells
- Enteroendocrine cells
What are stem cells?
Stem cells are cells that reside in crypts that constantly divide to replace epithelia
Where are paneth cells found and what do they do?
- Location: base of crypts
- Function: secrete antibacterial proteins to protect stem cells
How can paneth cells be identified?
Paneth cells contain vesicles which stain red
Where are enteroendocrine cells found and what do they do?
- Location: deeper in crypts and gastric glands
- Function: secrete hormones that control the function of the gut e.g gastrin, CCK, secretin
Briefly, identify states where crypts are affected by inflammatory bowel disease
- Crypt alteration
- Cryptitis – inflammation of wall
- Crypt abscess – neutrophils in lumen
Describe the organisation of glandular tissue in the gut
- Organised secretory cells – acini and tubules
- Connected to a duct
Provide 3 examples of exocrine glands in the gut
- Salivary glands
- Pancreas
- Brunners glands
Differentiate between the secretions of acini and tubules
- Acini secrete serous secretions (+ enzymes)
- Tubules secrete mucous e.g. Brunner’s glands
What type of secretions do salivary glands produce?
- Serous secretions
- Mucous secretions
Describe the pathophysiology of ulceration of the gut
- Erosion through muscularis mucosae
- Failure of protective mechanisms e.g. mucus production
Describe the pathophysiology of Coeliac’s disease
- Inability to tolerate gliadin
- Damages mucosa
- Results in poor digestion and malabsorption
Identify the 5 layers composing the abdominal wall
- Skin
- Fascia/fat: superficial and deep
- Anterolateral muscles
- Transversalis fascia
- Peritoneum
Identify the 4 anterolateral muscles composing part of the abdominal wall
- External oblique
- Rectus abdominis
- Internal oblique
- Transverse abdominis
What is an aponeurosis?
An aponeurosis is a thin sheet-like tendon
What is the rectus sheath?
The rectus sheath is the aponeurosis of the lateral muscles surrounding the rectus abdominis
What is the arcuate line of the rectus sheath and why is it significant?
- The arcuate line is the lower limit of the posterior layer of rectus sheath
- It is the point at which inferior epigastric vessels pierce rectus abdominus, found half way between the umbilicus and pubic crest
What is the mesentery?
The mesentery is a double fold of peritoneum that attaches certain viscera to the posterior abdominal wall
What does the mesentery contain?
- Blood vessels
- Lymph vessels
- Nerves
- Fat
Provide two definitions of a peritoneal ligament
A peritoneal ligament is:
- A double fold of peritoneum that connects two viscera together
- A double fold of peritoneum that connects a viscera to the abdominal wall
Provide two examples of peritoneal ligaments that connect 2 viscera together
- Gastrocolic ligament: stomach to transverse colon
- Gastrosplenic ligament: stomach to spleen
Provide two examples of peritoneal ligaments that connect a viscera to the abdominal wall
- Falciform ligament: liver to anterior abdominal wall
- Triangular ligaments: liver to diaphragm
What are omenta?
Omenta are double folds of peritoneum
Where is the greater omentum found?
Greater omentum hangs down off the greater curve of the stomach
Where is the lesser omentum found?
Lesser omentum connects lesser curve of stomach to liver
Identify the 3 purposes of a sphincter
- Divide tube into sections
- Control movement along the tube
- Prevent reflux of material
Identify 6 sphincters found in the human body
- Upper oesophageal
- Lower oesophageal
- Pyloric sphincter
- Sphincter of Oddi
- Ileo-caecal (valve)
- Anal sphincter: internal and external
Majority of the sphincters in the body are under autonomic control.
Identify the sphincter which is under somatic control
External anal sphincter is under voluntary control
Identify 4 consequences of sphincter failure in the GI tract
- Duodenal ulceration
- Reflux
- Incontinence
- Dysphagia
Blood supply to the gut comes from three branches of the aorta.
Identify them
- Coeliac trunk
- Superior mesenteric artery
- Inferior mesenteric artery
Describe the venous drainage of the gut
All venous drainage goes to liver via the hepatic portal vein
How much fluid should there be in the peritoneal cavity?
20 - 25 ml
Identify and describe 2 differences between the ileum and jejunum
- Ileum has more lymphoid tissue because it is near the large colon and needs protection from the bacteria
- Jejunum is more vascular (red) and has a greater surface area as it is the main site of transport and absorption
