Jejunum, Ileum and Colon Flashcards
Deglutition
swallowing
Divisions of small intestine
duodenum
ileum
jejunum
measurement of:
duodenum
ileum
jejunum
first 25cm
- 5m
- 5m
ILEUM
- Feels like
- colour
- located
single wall
paler (Peyers patches)
Mainly in the lower R quadrant
Modifications to Increase Surface Area
- Plicae circulares
- Villi
- Microvilli
Plicae circulares
circular folds
villi contain
capillaries and lacteals.
Folds of the mucosa
Microvilli:
folds of cell membranes of absorptive cells
Lacteal
network of blood and lymph capillaries found in villi
how do carbs and proteins get into blood to liver
via hepatic portal vein
-Fat into lymph
fat-soluble toxins circulate systemically b4 going to liver for
detoxification
Arterial supply
Terminal branches of SMA
→ arterial arcades
→ vasa recta
Venous drainage
tributaries of SMV
Lymphatic drainage
SM lymph nodes.
LARGE INTESTINE
extends from
consists of
from ileocecal junction to anus
cecum, colon, rectum, anal canal
features of large intestine
✓ Absence of villi
✓ Presence of goblet cells
✓ Deep intestinal glands
large intestine movements are
sluggish (18-24 hours)
large intestine function
Absorption of water and salts,
secretion of mucus
extensive action of microorganisms.
how much chyme enter the cecum
1500 mL
% of volume reabsorbed
yielding
90
80-150mL of faeces
large intestine absorbs
water and electrolytes
Ileocaecal fold
where Ileum joins the large intestine
Ileo-caecal valve
sphincter formed by the extension of smooth muscle from the ileum
position of caecum
inf to the ileocaecal opening.
Appendix is attached to the
postero-medial wall of the caecum
Blood supply to caecum and appendix is derived from
SMA
Teniae coli
: 3 longitudinal muscle bands
Appendices epiploicae
short peritoneal fold filled with fat
peritoneal folds that have mesentery
Appendix, transverse & sigmoid colon
Cecum covered..
completely by peritoneum, but has no mesentery
Ascending & descending colon covered
by peritoneum anteriorly & on the sides
Ascending, transverse, descending and sigmoid colon
Arterial supply
Ascending and proximal two-thirds by SMA
- Ileocolic
- Right colic
- Middle colic
Ascending, transverse, descending and sigmoid colon
Venous drainage
tributaries of SMV & IMV
Lymphatic drainage
- Lymph channels follow the arteries
SM and IM lymph nodes.
RECTUM
located
description
follows
S3
thick muscular tunic 15 cm long
sacrococcygeal curve
rectum: concavity is maintained by
puborectal sling
Houston’s valves
what are they
what do they do
semi-lunar transverse folds of rectal wall
protrude into the rectum and overlap
Houston’s valves function
support weight of faecal matter
Houston’s valves
- width
- made of
- supplied by
12mm
circular muscle coat of the rectum
sup,middle ,inf. rectal arteries
where does the anus begin
where muscles pass through pelvic diaphragm
Muscles of the anus are
(1) The external sphincter.
(2) The pubo-rectalis muscle
(3) The longitudinal muscle of the rectum.
(4) The internal sphincter.
In Anal canal
superior epithelium is
inferior epithelium is
simple columnar
stratified squamous
Internal anal sphincter muscle is
smooth
External anal sphincter muscle is
skeletal muscle
what is Hemorrhoids
Vein enlargement or inflammation
Colon/Rectum covered by peritoneum
– Cecum
– Transverse
– Sigmoid
– Anterior descending and ascending
Colon/Rectum NOT covered by peritoneum
post ascending and descending
Secretions of the Small Intestine
Mucus
Digestive enzymes
Brunner’s glands
function of mucus
Protects against digestive enzymes and stomach acids
Brunner’s glands
aka
what are they
Stimulated by
- Duodenal glands
- tubular mucous glands of the submucosa
- vagus nerve, secretin, chemical or tactile irritation of duodenal mucosa
Intestinal crypts (of Lieberkuhn)
- what
- where
- cells divide
- secrete
- tubular glands in mucosa
- inbetween villi
- every 3-6 days to renew epithelium
- watery intestinal juice which mixes with chyme
Intestinal flora
- what is it
- produce
permanent normal bacteria
vitamins, e.g. K, which get absorbed
Hormones
Cholecystokinin stimulates… to release….
Secretin stimulates… to release….
GB and pancreas to release stored bile
pancreatic ducts to release acid neutralizer
Cells of mucosa
Absorptive cells
Goblet cells
Endocrine cells
Granular cells (paneth cells)
Absorptive cells w micro villi
what do they do
where
produce digestive enzymes and absorb digested food
small intestine
goblet cells
produce
where
protective mucus
colon
Endocrine cells produce
regulatory hormones
Granular cells (paneth cells): function
protect from bacteria
JEJUNUM
feels like
contains
located
double wall..thicker than ileum
plicae circulares
mostly upper left quadrant
