Byfdjpkc.fudan.edu.cn/_upload/article/files/2a/2d/074a...PowerPoint Presentation Author Chun-min...
Transcript of Byfdjpkc.fudan.edu.cn/_upload/article/files/2a/2d/074a...PowerPoint Presentation Author Chun-min...
DIG
ES
TIV
E S
YS
TE
M
By Chunmin LIANG & James Williams
What will happen if a little bean
is swallowed by you?
Please write a story by yourself.
I will provide you a chance for presentation
if it is convincing enough.
A little bean
Team work
General Function Of Digestive Tract
• Ingestion
• Mastication
• Motility
• Secretion
• Hormone release
• Chemical digestion
(from macromolecules to smaller molecules)
• Absorption (into blood and lymph)
• Elimination
General structure :
1. Mucosa
2. Submucosa
3. Muscularis
4. Serosa
The mucosa comprises:
Epithelium
Muscularis mucosae: a thin layer of smooth muscle seperating
mucosa from submucosa
Lamina propria: loose CT rich in blood vessels,
lymphatics, lymphocytes, smooth
muscle cells and often small glands
The submucosa contains :
Connective tissue layer with
①larger blood and lymph vessels
②submucosal plexus(nerves)
③sometimes glands
④lymphoid tissues
Mucosal Immune System,MIS
(mucosal-associated lymphoid
tissue,MALT):
lymphoid tissues distributed in the
mucosa of digestive tract ,
respiratory tract、et al.
The first barrier against microbial invaders
50% of lymphoid tissues located in MALT
Pre-
plasma cell Lymph
nodes
Thoracic
duct Blood
Circulate back
to gut mucosa Plasma cell
Recirculation of lymphocytes
Lymphoid
nodules IgA
SP(secretory piece)
sIgA
Key point: How to understand the immune response in digestive tract?
antigen
M cell
lymphocyte
macrophage
Pre-
plasma cell Memory
B cell
Pre-
plasma cell
The Muscularis :
Smooth muscle,
consists of two layers
①Inner circular
②External longitudinal
The Serosa:
① can be “true serosa” (with a covering of
mesothelium)
② or “fibrosa” (without mesothelium)
Congenital megocolon
Tongue
Mucosa:
There are mainly 4 types of papillae
① Filiform papillae
② Fungiform papillae
③ Vallate papillae
④ Foliate papillae
Skeletal muscle
Cross each other in 3 planes
Providing the flexibility for speech,
positioning food,chewing and swallowing.
The comparation of 4 different papilla
Types Quantity Structural characteristics
Filiform
Most
numerous Sharp,partly keratinized,
lacking taste buds
Fungiform
Less Resemble mushroom,
has taste buds on its expanded
upper surface
Vallate
Least
numerous Largest,near the V-shaped
groove, have more numerous
taste buds (≥1/2 )
Foliate
papillae
Less poorly developed,
on the sides of tongue
Taste bud • Ovoid structure
• Each containing 50-75 cells
• Located in stratified epithelium of
the tongue and oral mucosa
The structure and function of taste bud
Salty
Sour
Sweet
Bitter (Half,elongated)
(Slender)
(Stem cells) Stem cells divide and
give rise to the other
two types
(apical)
(sensory axon form synapse with taste cell)
molecules (tastants) dissolved in saliva
Esophagus
Epithelium is stratified
squamous, non-keratinized
Submucosa has glands
(mucous)
Muscularis mucosae made of longitudinal bundles of smooth muscle
Serosa has mesothelium only within abdominal cavity
Muscularis externa can have skeletal and/or smooth muscle
Upper 1/3: skeletal muscle
Middle 1/3: mixed
Lower 1/3: smooth muscle
Mucosa and submucosa swell into the lumen to form
longitudinal ruga.
Stratified squamous, non-keratinized epithelium
Submucosa has glands (mucous)
Muscularis externa have skeletal
and/or smooth muscle
Traveling from esophagus to stomach,
the little bean finds that...the epithelium has changed!
Super!
Abrupt transition from stratified squamous epithelium to
simple columnar epithelium
The structures of Stomach
Gastric glands
mucosa submucosa muscularis serosa
Surface of mucosa covered with
simple columnar epithelium
Submucosal nerve plexus
Myenteric nerve plexus
Stomach • Is a mixed exocrine-endocrine organ
• Digests food
☆ continue the digestion of carbohydrates
☆ add acidic fluid to the ingested food
☆ transform food into a viscous mass
(chyme) by muscular activity
☆ promote the initial digestion of proteins by pepsin
• Secretes hormones
Famous HCl: hydrochloric acid
Pylorus Fundus/Body Cardia
Stomach ①
②
③
④
There are 4 regions with
different gastric glands...
(Deep pits and short glands)
Lamina
propria
Fundic glands
Muscularis mucosa
HCl and pepsin are mainly secreted in the
body and fundus regions
Cells in fundic gland
1.Surface mucous cells secret neutral mucus against
acidic gastric fluid
2.Mucous neck cells secret acidic mucus in the
top area of the gland
3.Parietal cells secret HCl and intrinsic
factor mainly in the upper
part of the gland
4.Chief cells secret pepsinogen in the
base of the gland
5.Enteroendocrine cells 6.Undifferentiated cells (stem cells)
?
...equiped with mitochondria and tubulovesicles
Intracellular secretory canaliculus
Parietal cell
Active
Under the observation of electron microscope
Rich in mitochondria
hydrochloric acid
FIGURE 15-19
The main steps in the synthesis of HCl
by parietal cell
Carbonic anhydrase
CO2 H2O + H2CO3 H+ + HCO3-
Intracellular canaliculus
Cl-
exchange
H+
Energy-dependent
+
HCl
( Hydrochloric acid )
pepsinogen pepsin
Chief cell
also named as zymogenic cell
Predominant in the lower
region of glands
Home work The comparation of 3 different cells
Types
Distribution L.M.
E.M.
Function
Parietal
cell
Chief cell
Neck
mucous
cell
?
( please send your answers to me by e-mail )
Inner layer
circular
Outer layer
longitudinal
Small Intestine: includes the duodenum, jejunum and ileum.
Mucosa
Submucosa
Muscularis
(2 layers)
Serosa
Villi
Central lacteal
Blood vessels
Intestinal gland
FIGURE 15-28
Observed by scanning electron microscope
Villi and Intestinal glands
Villus Absorptive cell
Striated border = microvilli = increase the absorptive surface area 20-fold
L.M. E.M. Function
Absorptive cell
central lacteal
Filled with
chylomicron
Demonstrated by your microscope, you will find…
Transport absorbed lipid into circulatory system…
Goblet cell
Acidic mucus
• Lie between the absorptive cells
• Increasing in number from duodenum to ileum
• Secrete acidic mucus for protection
from A. pancreatic enzymes
B. impeding bacterial invasion
Paneth cell
• Only found in intestinal glands
• Lies in the base of gland
• L.M. ---Acidophilic granules
• E.M.---RER, Golgi complexes
• Play antibacterial effects
Undifferentiated cell
Acidophilic secretory granules
contain lysozyme and defensin
Fight against
bacterial invasion
intestinal gland
The comparation
of 3 segments
Could you distinguish them,
Which is which?
duodenum, jejunum and ileum.
Key point: Which structures of small intestine are related with the
increased surface for enhancing absorption ?
Length:
Plica circulares: composed of mucosa and submucosa
Villi:
Apical microvilli:(striated border)
20-fold
10-fold
3-fold
Composed of epithelium and lamina propria
12 to 24 feet
So, as to my little bean, it is absolutely a long trip...
Large intestine (colon)
• no villi
• abundant goblet cells
• abundant large deep intestinal glands(crypts)
• absorptive cells have irregular short microvilli
• more lymphoid tissues in the lamina propria
Appendix
• narrow fingerlike
• at the inferior of cecum
• smaller and irregular lumen
• fewer and shorter crypts
• has no tenia coli
• masses of lymphatic tissue
in mucosa and submucosa
appendicitis If our little bean hides here,
what will happen?
The border of rectum and anal canal
Look!
The little bean was happy because he believed he arrived a new place…
Hey!! I still
alive!!