University:
Glendale Community College
Course:
BIO160 | Introduction to Human Anatomy and Physiology
Academic year:

2019
Views:

172

Pages:

5
Author:

brnknoutel

Gross Anatomy of Small Intestine • Duodenum curves around head of pancreas – approximately 10 inches or “12 fingers” long • Greek 14th Century “intestinum duodenum digitorum” – retroperitoneal along with pancreas – receives stomach contents, pancreatic juice and bile • Jejunum is next 8 ft. (in upper abdomen) – covered with serosa and suspended by mesentery • Ileum is last 12 ft. (in lower abdomen) – covered with serosa and suspended by mesentery – ends at ileocecal junction with large intestine Gross Anatomy of the Small Intestine Surface Area of Small Intestine • Plicae Circulares (circular folds) up to 10 mm tall – increase surface area 3 x vs a smooth tube • Villi are fingerlike projections 1 mm tall on the plicae circulares – covered with absorptive epithelium and contain blood vessels, lymphatics (lacteals), smooth muscle fibers – increase SA 10 x • Microvilli 1 micron tall – folds of plasma membrane on absorptive cells forms a brush border supported by actin microfilaments – increase SA 20 x Plicae Circulares, Villi and Microvilli Absorbtive Cells Mucous Microvilli Goblet cell Intestinal Crypts • Pores opening between villi lead to intestinal crypts (of Lieberkuhn) – crypts are lined with absorptive cells, goblet cells, Paneth cells and rapidly dividing cells at the base – life span of cells is 3-6 days as cells migrate up to surface and get sloughed off and digested – Paneth cells produce antibacterial secretions