Small Intestine To Large Intestine Flashcards
• A long tube-like organ that connects the stomach and the large intestine
• It helps to further digest food coming from the stomach.
Small intestine
It absorbs nutrients (vitamins, minerals, carbohydrates, fats, proteins) and water from food so they can be used by the body.
Small intestine
Three segments of small intestine
duodenum, jejunum, and ileum
SMALL INTESTINE: SURFACE MODIFICATION
Epithelium
Plicae circularis
Villi
Striated/ brushed border on villus
Ridge of mucosa and submucosa in small intestine
Plicae circularis
Projection of the mucosa epithelium with lamina propria core in small intestine
Villi
• Microvilli on the apical surface of columnar epithelial cells in small intestine
Striated/brushed border on villus
Plicae circulares also known as
Valves of Kerckring
valvulae conniventes
horizontal mucosal folds
Horizontal folds that are seen grossly
Core of submucosa and a covering of mucosa
Most developed in jejunum
Absent in first part of duodenum and distal half of ileum
Valves of Kerckring
plicae circulares
Fingerlike projections on surface of plicae circulares
Intestinal Villi
Abundant in proximal segments of small intestine
Often absent in distal ileum
Made up of epithelium and lamina propria
Intestinal Villi
Core of villi has______ (lymphatic capillary that end blindly near the tip of each intestinal villus)
lacteal
• T-cells in between epithelial cells
Intraepithelial lymphocytes (IEL)
Cell types in intestinal villi
1) absorptive cells (enterocytes)
2) goblet cells
3) enteroendocrine (argentaffin) cells
4) M-cells
Cell types on villi:
Most numerous
Columnar cells with microvilli (brush border; striated border)
Microvilli consist of a core of actin filaments that are enveloped by cell membrane
Absorptive cells (Enterocytes)
Cell types on villi:
Among absorptive cells
Number increases as one goes distally
Secrete mucus to protect and lubricate the lining
Goblet cells
Cell types on villi:
Scattered over entire epithelium
Columnar with microvilli
Secrete numerous regulatory
hormones for the digestive system
Enteroendocrine (argentaffin) cells
Cell types on villi:
Scattered over entire epithelium
Located at the base of intestinal glands
Secretes lysozyme and defensins thus provide host defense against microbes
Paneth cells
Paneth cells secrete
Secretes lysozyme and defensins thus provide host defense against microbes
Intestinal villi: Lamina propria of small intestine
Has…
crypts of Lieberkuhn
Simple tubular glands
Invagination of epithelium into lamina propria
Ducts open between adjacent villi
Lined by low columnar epithelium
Crypts of Lieberkuhn
The only glands in submucosa of small intestine
Glands of Brunner
Confined to submucosa of duodenum
Compound coiled tubular, mucus-secreting glands
Ducts open into bottoms of Crypts of Lieberkuhn
Glands of Brunner
Glands of Brunner secretes
Mucus
Epidermal growth factor (EGF)
Large aggregates of lymphoid nodules in ileum
M-cells (membranous epithelial cells)
Peyer’s patches
SMALL INTESTINE: MUSCULARIS EXTERNA
Muscle fibers:
Inner circularly arranged
Outer longitudinally arranged smooth muscle cells
With myenteric plexus of______
auerbach
SMALL INTESTINE: ADVENTITIA OR SEROSA
__________
Posterior aspect of 2nd and 3rd segments of duodenum
___________
Rest of small intestine
Adventitia
Serosa
Distinct histological features of the small intestine:
- Plicae circularis, villi & microvilli - increases functional surface area
- Phagocytic Paneth cells in intestinal gland/crypt
- Brunner’s Glands in the submucosa of the duodenum
- Peyer’s patches of lymphoid tissue in ileum
Long, tube-like organ that is connected to the small intestine at one end and the anus at the other.
Large intestine
Portion of the digestive system most responsible for absorption of water and electrolytes
Large intestine
Segments of large intestine
Cecum and vermiform appendix
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anal canal
Large intestine Grossly differs from small intestine because of:
Sacculations or haustra
Appendices epiploicae
Teniae coli
Cells in the mucosa of large intestine:
• Majority of cells; abortive in nature
With shorter microvilli than in small intestine
Enterocytes
Cells in the mucosa of large intestine:
• More numerous than in small intestine
Goblet cells
Cells in the mucosa of large intestine:
Fewer than in small intestine
Secrete glucagon, serotonin, somatostatin and pancreatic polypeptide
Enteroendocrine cells
Cells in the mucosa of large intestine:
Similar to those in small intestine
M-cells
In large intestine ______
GALT has more lymphoid nodules than small intestine and can extend to submucosa
Lamina propria
__________ compared to small intestine:
Longer
More goblet cells
No Paneth cells
Crypts of Lieberkuhn
LARGE INTESTINE: MUSCULARIS EXTERNA
Outer layer of longitudinallyarranged smooth muscle fibers form three narrow bands
Are about 1 cm in width each and equidistant from each other
Tenia coli
Large intestine
Inner circular smooth muscle -
haustration
3 thick bands of longitudinal smooth muscle in large intestine
taenia coli
Large intestine is adventitia? Or serosa? Mostly
Serosa
____________ in large intestine is only in parts of ascending colon and descending colon that press directly on posterior body wall
Adventitia
In serosa of large intestine - adipose tissue form pendulous masses called
appendices epiploicae
Distinct histological features of the large intestine:
- Microvilli only - increase functional surface area
- Abundance of goblet cells in epithelium for lubrication
- Tenia coli of muscularis externa
Lacks villi, has few glands, has lymphoid nodules in the lamina propria,
Incomplete muscularis mucosae
Thick submucosa, thin muscularis and no teniae coli
Appendix
