Cells of the Alimentary Canal Flashcards
Consists of the epithelium lamina propria, and muscularis mucosae
Mucosa
The submucosa consists of
Connective tissue
Usually consists of 2 coats, an inner circular muscle coat and an outer longitudinal muscle coat
Muscularis externa
The serosa or adventitia covers the
Gut wall
Exhibits stratified squamous epithelium and a highly developed muscularis externa
Esophagus
Located at the posterior or posteriolateral aspect of the trachea
Esophagus
The outermost layer of the esophagus, the adventitia, is continuous with the adventitia of the trachea that holds both organs in place in the
Body wall
In the esophagus, glands are present in the
Lamina propria or sub mucosa
Esophageal glands near the stomach protect the esophagus from
Gastric contents
The upper esophagus has which type of muscle?
Striated
The lower esophagus has which type of muscle?
Smooth
The middle esophagus has which type of muscle?
Mixture of striated and smooth
Characterized by a mucosa with increased surface area due to gastric pits and gastric glands
Stomach
In addition, the stomach mucosa is thrown into transient folds called
Rugae
In the stomach, which cells produce granules that contain glycoproteins (mucins) that combine with water to form a protective and insoluble gel?
Surface mucous cells
Surface mucous cells also produce
-diffuse into the surface mucous gel
HCO3-
In the stomach, which cells produce a soluble mucous?
Neck mucous cells
In the stomach, which cells produce HCl, HCO3-, and intrinsic factor?
Parietal cells
A glycoprotein that complexes with vitamin B12 in the stomach and duodenum
-Essential for B12 absorption in the ileum
Intrinsic factor
Important for red blood cell development
B12
Without B12, a person can develop
Pernicious anemia
To carry out the job of producing acid, the parietal cells exhibit dramatic
Plasticity
When the parietal cell is not activated, the plasma membrane is organized into
Intracellular tubules and vesicles
When the parietal cell is activated, these structures coalesce into an intracellular canaliculus, which is a huge surface through which
H+ and Cl- can move into the lumen
The parietal cell is stimulted by
ACh, Histamine, and Gastrin
Activation of one of these effectors potentiates the activity of the
Others
Responsible for the production of pepsinogen and gastric lipase
Chief cells
Chief cells are stimulated by
Neural stimulation and secretin
Chief cells are typically protein producing cells and are characterized by having a prominent
Golgi and rER
Produced as a proenzyme
Pepsin
Increase blood flow and HCO3- secretion
Prostaglandins
Under stressful conditions, the taking of aspirin and NSAIDS inhibit the protective effects of the
Prostaglandins
Cells found in multiple locations in the GI tract, which influence gut function by coordinating the function of the different organs that make up the gut
Diffuse Neuroendocrine System (DNES) cells
The DNES produces hormones that are predominantly members of the
Cholecystokinin/gastrin family or secretin/glucagon family
Secrete hormones into the extracellular matrix where they enter capillaries in the lamina propria
DNES
A key feature of the stomach that helps distinguish it from other organs is that the stomach is made up of
3 layers of muscle
The mucosa surface area of the small intestine is increased by
Villus projections and Crypt of Langerhans invaginations
In addition, the submucosa of the small intestine is folded into permanent folds called
Plicae circularis
The apical surface of the epithelial cells of the small intestine is also folded into
Microvilli
Intestinal cell that is responsible for absorption of lipids, sugars, amino acids, vitamins, minerals, ions, and water
Enterocytre
Produces transmembrane enzymes that are responsible for the terminal digestion of proteins and carbohydrates
Enterocyte
Produce a protective layer of mucous in the small intestine to protect it from enzymatic digestion
Goblet cells
Replace epithelial cells as they die in the small intestine
Stem cells
Small intestine cells that produce lysozyme as well as TNF-a, defensins, and cryptidins
Paneth cells
Anti-bacterial enzyme that controls the gut flora
-stored in granules and released into the gut lumen
Lysozyme
Defensins and cryptidins have which type of effect?
Antimicrobial effect
Protection of the intestine from antigens is also due to the presence of a well developed immune system referred to as
Gut Associated Lymphoid Tissue (GALT)
These immune cells are located throughout the gut and become more and more evident as you descend the small intestine and enter the
Large intestine
Organized as diffuse lymphatic tissue, solitary nodules, or aggregated nodules
GALT immune cells
In the lower parts of the intestine, these nodules are called
Peyer’s Patches
Evident over nodules in follicle associated epithelium
M Cells
Transport antigens to underlying immune cells
M cells
This results in the activation of lymph cells that travel to the lymph nodes where they are stimulated to
Proliferate
The lymphocytes can travel to the lamina propria and differentiate into plasma cells that produce
IgA and IgE
Transcytosed across the epithelium to the lumen, where it decreases adherence of foreign material to the epithelium and neutralizes viruses and bacterially produced toxins
IgA
Can also go into the liver where it is complexed to secretory component and released into bile
IgA
Decreases adherence of foreign material epithelium, neutralizes viruses and bacterially produced toxins
IgA
DNES cells are also found in the small intestine, particularly in the
Crypts of Lieberkuhn
To carry out its function, much of the large intestine exhibits a simple columnar epithelium made up of
Absorptive cells, goblet cells, and stem cells
The large intestine also contains
Immune cells and DNES cells
Increases as we descend the large intestine
The number of lymphocytes and goblet cells
In the anal canal, the simple columnar epithelium changes to become
Stratified squamous epithelium
Surface area is increased in the large intestine by the presence of crypts in the mucosa and folds of submucosa called
Plicae semilunaris
The external longitudinal muscle coat of the colon is modified to form
Teniae coli
In the anal canal, the circular smooth muscle sphincter is the
Internal anal sphincter
The enteric nervous system consists of the
Submucosal (Meissner’s) plexus and the Myenteric (Auerbach’s) Plexus
Can sense chemicals and material in the lumen
Sensory fibers in the lamina propria
These sensory fibers have cell bodies in the submucosa and they can signal the
Myenteric plexus as well as the muscularis mucosae glands
Can stimulate contraction of the muscularis externa as well as send signals back to the submucosal neurons
Myenteric plexus neurons
