Term
| What are the layers of the lower GI? |
|
Definition
1) Mucosa
2) Submucosa
3) Muscularis externa
4) Serosa or fibrosa
5) Extrinsic glands |
|
|
Term
| What are the layers of the Mucosa? |
|
Definition
1) Epithelium
2) Lamina propria
3) muscularis mucosa |
|
|
Term
| Describe the epithelium of the Mucosa of the lower GI: |
|
Definition
1) faces lumen
2) various types
- correlated with function performed
3) strat. squam. in esophagus & anal canal
4) simple columnar in stomach & intestine
5) basal lamina underlies epithelium |
|
|
Term
| Describe the lamina propria of mucosa of lower GI: |
|
Definition
1) loose CT contains BV's, nerves, lymphoid tissue
2) glands sometimes present |
|
|
Term
| Describe the muscular mucosa of the lower GI: |
|
Definition
1) 2 layers of smooth muscle
- inner circular
- outer longitudinal (not always distinct)
2) Single longitudinal layer in esophagus |
|
|
Term
| What type of tissue is in the submucosa of lower GI: |
|
Definition
1) loose CT
2) lymphoid tissue
3) larger BV's
4) nerves |
|
|
Term
| What type of nervous innervation is found in submucosa of lower GI? |
|
Definition
1) Small autonomic ganglia
- symp. & parasymp. fibers
- post-G. parasymp. neurons
- collectively referred to as Meissner's plexus
2) Glands sometimes present |
|
|
Term
| What type of muscle is predominantly found in muscularis externa? |
|
Definition
Smooth muscle except in upper 2/3 of esophagus
1) Generally composed of inner circular layer
- controls size of lumen
2) Outer longitudinal layer
- shortens tube locally |
|
|
Term
| Describe muscularis externa of lower GI: |
|
Definition
1) Often relatively thick distinct layers
- except in stomach
- 3 less distinct layers |
|
|
Term
| How is the muscularis externa of lower GI innervated? |
|
Definition
1) A nerve plexus & autonomic ganglia
- sym. & parasym. fibers
- post-G parasym. neurons
- collectively referred to as myenteric plexus or Auerbach's plexus
- commonly lie between the layers |
|
|
Term
| Describe the serosa or fibrosa of lower GI: |
|
Definition
1) if retroperitoneal:
- adventitia or fibrosa (CT)
2) Otherwise continuous w/ mesentery
- CT covered by serosa or mesothelium on outer surface |
|
|
Term
| What are the extrinsic glands of lower GI: |
|
Definition
1) Liver
2) Gall bladder
3) pancreas
4) located outside GI tract w/ ducts that empty into duodenum |
|
|
Term
| What are the two main functions of the GI tract? |
|
Definition
|
|
Term
| Where are Microfold (M) cells found? |
|
Definition
|
|
Term
| What is the function of M cells? |
|
Definition
1) Take up antigens by endocytosis
2) transfer them to underlying by exocytosis
- transcytosis
3) Nuclei located near base of epithelial layer
- they extend processes & fold over lymphocytes that migrate into the lamina propria
4) Lymphocytes exposed to antigens in extracellular space
5) luminal surface of M cells extend processes to take up foreign substances |
|
|
Term
| What are the two types of diffuse lymphatics in lower GI: |
|
Definition
1) GALT
- lamina propria
- gut associated lymphatic tissue
2) MALT
- lamina propria
- mucous associated lymphatic tissue |
|
|
Term
| What happens in diffuse lymphatic tissue? |
|
Definition
1) The Lcytes that were exposed to Ag's by M cell's are turned into plasma cells & produce Ab's
2) lamina propria contains many Lcytes & plasma cells |
|
|
Term
|
Definition
| 1) Trigger mast cells to release histamine |
|
|
Term
|
Definition
| 1) Travel in lymph to react w/ Ag's throughout body |
|
|
Term
|
Definition
| 1) Transferred back by transcytosis into secretions like saliva & milk |
|
|
Term
|
Definition
1) lamina propria of esophagus
2) eosiniophilic granules
3) single nucleus |
|
|
Term
|
Definition
1) eosinophilic granules, bilobed nucleus
2) lamina propria of stomach |
|
|
Term
| What are Peyer's patches? |
|
Definition
Found in regions of GI tract where Ab production is so intense that prominent lymph nodules are formed in lamina propria
1) Ileum |
|
|
Term
|
Definition
1) located in sm. intest.
2) secrete lysozyme
- antibacterial |
|
|
Term
| What is the function of the esophagus? |
|
Definition
1) transport of food bolus
2) ~10 in long
3) Transition from pharynx to esophagus
4) mucous glands in mucosa & submucosa
- lubricate passageway to aid in transporting food bolus to stomach |
|
|
Term
| Describe the structure of the Mucosa: |
|
Definition
1) Strat. squam. epithelium
2) Non-keratinized |
|
|
Term
| Describe the lamina propria of mucosa of esophagus: |
|
Definition
1) CT - poor in elasticity
- not highly cellular
2) thickness varies
3) mucous glands only near pharynx & stomach
- superficial esophageal glands
- cardiac glands |
|
|
Term
| Describe the muscularis mucosa : |
|
Definition
1) One longitudinal layer
2) mostly thicker than in other parts of GI except at top of esophagus
- absent or present in small slips of muscle |
|
|
Term
| Where are esophageal glands found? |
|
Definition
1) Submucosa
- tall papilla |
|
|
Term
| Where is the muscularis externa striated? |
|
Definition
1) upper 1/3 of esophagus
- cont. of pharynx
2) middle 1/3 is mixed
3) lower 1/3 all smooth |
|
|
Term
| What supplies the parasympathetic innervation of lower GI tract? |
|
Definition
1) Vagus nerve
- colon supplied by pelvic nerve
2) These nerves innervate parasym. ganglia in walls of GI tract |
|
|
Term
| What supplies sympathetic innervation to GI? |
|
Definition
1) Celiac, superior, inferior mesenteric ganglia
- send post-G fibers to the gut |
|
|
Term
|
Definition
1) wave of contraction of inner circular layer of m. externa
2) pushes food & accompanied by a dilation of the esophagus just before constriction
- caused by contraction of longitudinal muscles that shorten & expand the wall of the esophagus
3) cutting nerve supply (autonomic) to gut does not stop peristalsis |
|
|
