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FoundSci Unit 7 > Lower GI > Flashcards

Lower GI Flashcards

1
Q

What is the main function of the small intestine?

A

Absorption of nutrients

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2
Q

What are modifications in the small intestine that increase its surface area?

A
  1. Plicae circularis - permanent circular folds of mucosa and submucosa, numerous in duodenum and jejunum
  2. Intestinal Villi - processes of mucosa formed by epithelium and lamina propria
  3. Microvilli - located on apical surface of surface epithelium
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3
Q

What layers are in the small intestine typically?

A

Mucosa

Submucosa - duodenal glands in duodenum

Muscularis externa

Adentitia - parts of duodenum

Serosa - most

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4
Q

What is a typical submucosa like in the small intestine?

A

Lacks glands, except for duodenum

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5
Q

What is a typical muscularis externa like in the small intestine?

A

Typical of GI tube

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6
Q

What is a typical serosa like in the small intestine?

A

Most lined with serosa except for portions of duodenum

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7
Q

What is a typical mucosa in the small intestine?

A

Epithelium - simple columnar cells with well developed microvilli and striated border. Goblet cells present that secrete mucus for lubrication. T cells (intraepithelial lymphocytes)

Lamina propria - loose CT that extends into villi. Contains lacteals (lymphatic capillaries), intestinal glands, and unremarkable muscularis mucosae

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8
Q

What are the intestinal glands?

A

Crypts of Lieberkuhn

Lined by simple columnar epithelium on a basal lamina

Open into lumen of small intestine at base of and between villi

Simple tubular glands

Contain many cell types:
- paneth cells - part of immune response, secrete bactericidal agents and maintain intestinal flora
- goblet cells
- stem cells near base
- enteroendocrine (DNES) cells - secrete hormones

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9
Q

What makes the duodenum different from other parts of small intestine?

A

Presence of duodenal or Brunner’s glands in submucosa

Secrete bicarbonate mucus that neutralizes acidic chyme from stomach

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10
Q

What makes the jejunum different from other parts of the small intestine?

A

Lacks distinct distinguishing features

Plicae circulares well developed

Narrow villi

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11
Q

What makes the ileum different from other parts of the small intestine?

A

Transition from jejunum to ileum is gradual

Contains Peyer’s patches formed by lymphatic nodules

Patches contain M cells that function in antigen transport and immune response

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12
Q

What is the function of the large intestine?

A

Absorption of water and electrolytes

Elimination of waste

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13
Q

What layers are present in the large intestine?

A

Mucosa

Muscularis externa

Serosa

Adventitia

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14
Q

What are the characteristics of the mucosa of the large intestine?

A

Lacking villi

Surface cells with short, irregular microvilli

Intestinal glands numerous and longer

Goblet cells more numerous to lubricate fecal mass

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15
Q

What are the characteristics of the muscularis externa in the large intestine?

A

Inner layer is complete

Outer layer of smooth muscle reduced - 3 teniae coli

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16
Q

What are the characteristics of the serosa and adventitia of the large intestine?

A

Serosa lines most of the large intestine (intraperitoneal)

Part of rectum is retroperitoneal so it is lined with adventitia

17
Q

What is unique to the structure of the vermiform appendix?

A

Mucosa is typical of colon bt with fewer and short glands

Abundant lymphoid nodules in lamina propria and submucosa - suggest it plays a role in immune system

2 uniform layers of muscularis externa present but lacks teniae coli

18
Q

What is appendicitis and what can it be caused by?

A

Inflammation of vermiform appendix

Blockage of appendix leads to buildup of mucus, increase pressure, and rupture

Infection of mucosa causes inflammation and ulceration

19
Q

What is unique about the structure of the rectum?

A

Transverse rectal folds - folds of inner circular layer of muscularis externa

Longitudinal folds - folds of submucosa and mucosa that allow for distension

2 complete layers of of muscularis externa but no tenia coli

Adventitia and serosa - intraperitoneal lined with serosa and retroperitoneal lined with adventitia

20
Q

What is the function of the rectum?

A

Storage and voiding of waste

21
Q

What is the function of the anal canal?

A

Voiding of waste

22
Q

What is the structure of the anal canal?

A

Transition to stratified squamous epithelium, transition in innervation and in muscle type

Anal columns - columns of Morgagni, folds of submucosa and mucosa, superior border marks the rectoanal junction

Anal valves - compress sinuses

Anal sinuses - located behind valves, contain anal glands that secrete mucous for movement of feces

Pectinate line

Intersphincteric line - between internal and external sphincters

23
Q

What is the epithelium below and above the anal columns?

A

Simply columnar above

Simple cuboidal below

24
Q

What is the pectinate line? How does the epithelium change?

A

Formed by inferior border of anal columns and anal valves

Anal columns to pectinate line is simple cuboidal and muscularis mucosae terminates at pectinate line

Below pectinate line is stratified squamous epithelium

25
Q

What is the intersphincteric line? How does the epithelium change?

A

Divides internal from external anal sphincters

Internal anal sphincter - thickening of inner circular layer of muscularis externa

External anal sphincter - skeletal muscle

Pectinate line to intersphincteric line is nonkeratinized stratified squamous epithelium

Inferior to intersphincteric line is keratinized stratified squamous epithelium

26
Q

What is intestinal sprue?

A

Disorders of small intestine related to disruption of mucosa

Presents as malabsorption like weight loss, diarrhea, steatorrhea, anemia, and vitamin deficiencies

27
Q

What is celiac disease?

A

Inflammatory response triggered by gluten

Biopsy of small intestine necessary to confirm diagnosis

4 features: villus atrophy, disordered epithelial with atrophied microvilli, inflammation of lamina propria, and intestinal gland hyperplasia

28
Q

What is Hirschsprung’s Disease?

A

Congenital megacolon

Absence of enteric nerves in portion of bowel due to failure in migration of neural crest cells

Results in absence of peristalsis in affection portion of the gut

Feces backs up into functional bowel increasing diameter

FoundSci Unit 7 (14 decks)

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