Lecture 34: Lower GI Histology Flashcards
Duodenum
Villi: spatulate/leaf-like
Deep crypts of Lieberkuhn
Brunner’s glands present
Jejunum
Villi: long and narrow
Crypts of Lieberkuhn present
NO submucosal glands
Ileum
Villi: long and narrow, rounded at the tip
Crypts of Lieberkuhn present
NO submucosal glands
Crypts of Lieberkuhn
Simple tubular glands with intestinal mucosa; open between adjacent villi and extend to muscularis mucosa
Goblet cells
Secrete mucus, stem cells
Enterocytes
Columnar epithelial cells with basal nuclei, perinuclear Golgi, and apical brush border. Produce dissacharidases, enteropeptidases, and other enzymes which digest different types of food molecules and activate zymogens
Paneth cells
Basal crypt cells with eosinophilic granules; secrete lysozyme, defensins, and tumor necrosis factor alpha; may phagocytize some microorganisms to help regulate intestinal flora
Enteroendocrine cells
Stain with chromium, silver; produce peptide hormones and serotonin; may produce paracrine or autocrine secretions
Brunner’s glands
Form bicarbonate and mucus to neutralize gastric acid; found in the submucosa of the duodenum
What are the functions of the large intestine?
Secrete mucous/lubrication, absorption of fluid, formation of fecal mass, continuation of digestion
Occluding/tight junctions of GI tract
Protective mechanism that prevents toxic material from seeping back through gut wall and into lamina propria (which would cause infection)
Inner mucosal layer secreted by goblet cells
Contains antimicrobial proteins which resist microbial penetration
Rapid cell turnover
Protective mechanism that replaces cells lost in GI tract due to hostile environment
What are toll-like receptors?
Pattern recognition receptor which recognizes structurally conserved molecules broadly shared by pathogens (PAMPs); located on enterocytes
What is IgA’s role in defense of the gut tract?
Primary immunoglobulin released by GALT; IgA directly coats microorganisms, inhibiting them from binding to epithelium
Role of M cells in defense of gut tract
Sample particulate antigen and present to antigen presenting cells in underlying lamina propria
GALT
Gut Associated Lymphoid Tissue; contains aggregation of lymphocytes, eosinophils, neutrophils; contain appendix, Peyer’s patches, mesenteric lymph nodes
Peyer’s patches
Dome shaped lymphoid structures under mucosal surface with B and T-cell dependent areas and many HEVs
Which of the following best describes the olfactory mucosa?
A. Stratified columnar epithelium with goblet cells and a distinct basement membrane
B. Simple ciliated columnar epithelium with goblet cells and a distinct basement membrane
C. Stratified, non-keratinized epithelium lacking goblet cells with thick basement membrane
D. Pseudostratified ciliated columnar epithelium lacking goblet cells with no distinct basement membrane
D. Pseudostratified ciliated columnar epithelium lacking goblet cells with no distinct basement membrane
Which of the following is NOT a necessary part of the respiratory membrane?
A. pneumocyte I B. basal lamina of pneumocyte I C. dust cells D. basal lamina of endothelial cell E. endothelial cell
C. dust cells
Which of the following is characteristic of an arteriole?
A. Thick tunica adventitia and large lumen
B. Thick tunica media in relation to size of lumen
C. Thin tunica media and relatively large lumen
D. Large blood-filled lumen
E. Large amounts of elastic fibers in tunica media
B. Thick tunica media in relation to size of lumen
Where in the body of a normal, healthy individual would you expect most erythrophagocytosis to be occurring?
A. Marginal zone of spleen B. Medulla of thymus C. Hematopoietic cord in bone marrow D. Cords of Billroth in spleen E. Paratrabecular sinus in lymph node
D. Cords of Billroth in spleen
Which of the following sequences best describes the flow of RBCs through the spleen?
A. Trabecular arteries, central arteries, splenic arteries, penicillus, venous sinuses
B. Splenic artery, central arteries, trabecular arteries, venous sinuses, penicilus
C. Trabecular arteries, splenic arteries, central arteries, penicillus, venous sinuses
D. Splenic artery, trabecular arteries, central arteries, penicillus, venous sinuses
D. Splenic artery, trabecular arteries, central arteries, penicillus, venous sinuses
The simple cuboidal epithelium of this portion of the kidney tubule is composed of cells in the form of truncated pyramids which are characterized by basal striations that mark the location of the mitochondria
A. Proximal convoluted tubule
B. Descending thin segment of loop of Henle
C. Ascending thick segment of loop of Henle
D. Distal convoluted tubules
E. Collecting ducts
A. Proximal convoluted tubule
Renin is secreted by which of the following?
A. Liver B. Macula densa C. Atrial cells of heart D. Mesangial cells E. Juxtaglomerular cells
E. Juxtaglomerular cells
