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LECTURE. DIGESTIVE SYSTEM part 1 Oral cavity, esophagus & stomach. Department of histology, cytology and embryology KhNMU. General description and significance. The digestive tract is: a long tube extending from oral cavity to the anus and associated glands . - PowerPoint PPT Presentation
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DIGESTIVE SYSTEM part 1
Oral cavity, esophagus & stomach
Department of histology, cytology and embryology KhNMU
LECTURE
General description andGeneral description and significancesignificance
The digestive tract is: The digestive tract is: a long a long tubetube extending from extending from oral cavityoral cavity to the to the anusanus and and associated glandsassociated glands..
Main functions are: Main functions are: ingestion, fragmentation, ingestion, fragmentation, digestion, absorption of nutrientsdigestion, absorption of nutrients and and elimination of elimination of waste products.waste products.
Classification and embryogenesisClassification and embryogenesis
3 compartments:3 compartments: AnteriorAnterior Oral cavity, pharynx, Oral cavity, pharynx, esophagus esophagus
MiddleMiddle Gastrointestinal tract Gastrointestinal tract
PosteriorPosterior Last 1/3 rectum, anus Last 1/3 rectum, anus
EmbryogenesisEmbryogenesis
EmbryogenesisGut – from endoderm,
stomatodaeum, proctodaeum – from ectodermConnective tissue, muscles are from mesoderm
amnion
yolk sac
EmbryogenesisEmbryogenesis
Yolk Sac
Oral Plate
CloacalPlate
foregut
midgut
hindgut
Allantois
Heart
General plan of General plan of structurestructure FOUR principal membranes:FOUR principal membranes:
Mucosa: EpitheliumMucosa: Epithelium
Lamina propriaLamina propria
Muscularis mucosaeMuscularis mucosae SubmucosaSubmucosa Muscularis externaMuscularis externa Serosa or adventitiaSerosa or adventitia
1c
2
4
3a
2a
2b
3b
1a
1b
Mucosa: 1.epithelium (buccal)
Mucosa: 2. lamina propria – con.t. –nutrition, support, protection (GALT),
absorption, secrition (glands),
villi3. muscularis mucosae
Submucosa - Submucosa - con.t. - big bl.vessels, glands, nerve plexuses, lymphatic nodules,
provides motility of mucosa
Muscularis externa – circular, longitudinal layers
Serosa or adventitiaSerosa or adventitia
Oral Cavity Oral Cavity consists of a number of suborgansconsists of a number of suborgans
FunctionsFunctions::
Ingestion, Ingestion, STRUCTURESTRUCTURE::
Fragmentation Fragmentation 1. Mucosa1. Mucosa
Moistening Moistening 2. Submucosa2. Submucosa
Speech Speech (not always present ! )(not always present ! )
Facial expression Facial expression 3. Muscularis ext.3. Muscularis ext.
Sensory reception Sensory reception (facial muscles)(facial muscles)
Breathing Breathing 4. Adventitia4. Adventitia
(absent)(absent)
The The outer surfaceouter surface (skin) (skin) of the lip is covered by thin skin (ts). of the lip is covered by thin skin (ts).
The The inner inner surface (oral)surface (oral) is lined by a is lined by a mucosamucosa
The tThe transitional zoneransitional zone
oral side skin side
low mag.
oralskin
sk sk
sk
tsts
ss
ss
bv
sg
lpLipLip
LipLip
Vermilion - Vermilion - “red” transitional “red” transitional zonezone In newborn there are small villi for sucking In newborn there are small villi for sucking (Krok). (Krok).
The cheek is similar to the lipThe cheek is similar to the lip. .
red area
ss
p
bv
Tongue Tongue
EEpithelium (E) & underlying ct.pithelium (E) & underlying ct.
SSkeletal muscle (SM) runkeletal muscle (SM) runss in 3 planes. Embedded in the skeletal in 3 planes. Embedded in the skeletal muscle muscle lielie glands (G). glands (G).
PPapillae. Most numerous are conical, apillae. Most numerous are conical, keratinizedkeratinized filiformfiliform (f) (f) papillae; papillae; function – function – general sensationgeneral sensation
fungiformfungiform and and foliatefoliate papillae are scattered. papillae are scattered.
At the sulcus terminalis, lie 8 -12 large At the sulcus terminalis, lie 8 -12 large circumvallatecircumvallate papillae (C). papillae (C).
- - Taste sensationTaste sensation
E
SMG
Cf
Tongue, filiform & fungiform papillaeTongue, filiform & fungiform papillae
filifili
ctct
ss ss funginss
CCircumvallatircumvallate papillae papilla
TongueTongue
papilla with taste budspapilla with taste buds
high
med
fp
tb
TThe mucosa (m) is tightly bound to the bone (b)he mucosa (m) is tightly bound to the bone (b).. The The epithelium (ss) epithelium (ss) is disturbedis disturbed in chewing and swallowing in chewing and swallowing and so and so tends to be tends to be keratinizedkeratinized, and lamina propria , and lamina propria forms deep papillae, protruding in the epithelium.forms deep papillae, protruding in the epithelium.
Hard Hard PalatePalate
Maxillaunerupted tooth
hard palate
epithelium
m
b
ss
lowmed
Soft Soft palatepalate
smEpithelium
sg
oral cavity
Its upper surface faces the respiratory passages Its upper surface faces the respiratory passages - - pseudostratified epitheliumpseudostratified epithelium..
Facing oral cavity epithelium isFacing oral cavity epithelium is stratified squamous stratified squamous. . Krok !Krok !
Lingual Lingual TonsilTonsil
Lingual tonsil (T) Lingual tonsil (T) locateslocates on the dorsum of the tongue. on the dorsum of the tongue.
Together with palatine, pharyngeal tonsils form Together with palatine, pharyngeal tonsils form "ring"."ring".
At time of chronic inflammation may undergo At time of chronic inflammation may undergo tonsilectomy.tonsilectomy.
ssc
mg
sk
T
TOOTHTOOTH
ToothToothdevelopmendevelopmentt Enamel organ Enamel organ
(epith)(epith) AmeloblastsAmeloblasts EnamelEnamel Dental papillaDental papilla OdontoblastsOdontoblasts DentineDentine Dental sac –Dental sac –
cementum,cementum,
pulppulp
SALIVARY GLANDSSALIVARY GLANDS
SalivaSaliva: water, mucus, amylase, : water, mucus, amylase, lysozyme, a/b, ions lysozyme, a/b, ions
I. Large salivary glandsI. Large salivary glands
3 pairs: parotid, submandibular, sublingual 3 pairs: parotid, submandibular, sublingual
function - function - IN RESPONIN RESPONcece TO TOPARASYMPATHETIC ACTIVITYPARASYMPATHETIC ACTIVITY
II. Minor salivary glandsII. Minor salivary glandsffunction - CONTINUOUSLYunction - CONTINUOUSLY
General structureGeneral structure Compound branched acinar or acino-tubular Compound branched acinar or acino-tubular
glandsglands Connective tissue capsuleConnective tissue capsule Lobulated structureLobulated structure Lobules contain secretory units and small Lobules contain secretory units and small
ductsducts
Interlobular connective tissue with ducts and Interlobular connective tissue with ducts and vesselsvessels
5 Intercalated duct
Striated duct,
Next are interlobular and general
Mucous acinus
Serous acinus
Secretory unitSecretory unit
Myoepithelial cells (contractile)
surround secretory portions
and small ducts – intercalated and striated
Myoepithelial cells
Nucleus
ParotidParotid
high
lowlow
su
nRER
sd
The parotid is a serous The parotid is a serous gland secreting amylase. gland secreting amylase.
Secretory unit Secretory unit (s(suu)) is is acinaracinar. .
Pyramidal aPyramidal acinar cells have cinar cells have round basally-placed round basally-placed nuclei (n) with abundant nuclei (n) with abundant basal RERbasal RER
low
med
Sublingual Sublingual glandgland
This gland has This gland has mucous &mucous & mixed mixed secretory secretory unitunits but s but
mostly mucous.mostly mucous.high
me
med
id
itd
n
idsd
MixedMixed acinus with a acinus with a SSerous erous demilunedemilune
msu
msu
Submandibular glandSubmandibular gland
It is It is predominantly serous gland shows blue, predominantly serous gland shows blue, pure serous acini (sa) & pale, mucous pure serous acini (sa) & pale, mucous and and mixed with mixed with serous demilunes (m/s) serous demilunes (m/s)..
low
highmed
lobule
ided
sa
m/s
sublingual gland
Submandibular gland
Striated duct
demilune
Demilune
Intercalated duct
Parotid gland
Sublingual Sublingual glandgland
CompaCompare!re!
Demilune
Striated duct
Esophagus Esophagus (=(= PharynxPharynx))
6-7 longitudinal folds.6-7 longitudinal folds.
The muscularis externa. The muscularis externa.
The upper The upper 1/3rd1/3rd is composed of skeletal muscle; is composed of skeletal muscle; the lower the lower 1/3rd1/3rd - - smooth muscle; the middle smooth muscle; the middle 1/3rd1/3rd shows a blending of the two varieties of shows a blending of the two varieties of muscle.muscle.
Epithelium is stratified squamous nonkeratinizedEpithelium is stratified squamous nonkeratinized
Esophagus
1) Mucosa-epithelium, laminapropria & muscularis mucosae,2) Submucosa, 3) Muscularis externa 4) Adventitia
EsophagusEsophagus
Mucosal Mucosal cardiac cardiac glands (mg) are in the lamina propria (lp) glands (mg) are in the lamina propria (lp) (mm) in the upper and lower thirds of the esophagus(mm) in the upper and lower thirds of the esophagus. .
If they are not fully effective, the excessive reflux results in If they are not fully effective, the excessive reflux results in pyrosis (heartburn) – the rise of the gastric contents upward pyrosis (heartburn) – the rise of the gastric contents upward toward the neck.toward the neck.
mg
lp
ss
mm sm
me
EsophagusEsophagus
A mucous A mucous esophageal esophageal glandglands propers proper (mg) (mg)
lie in the submucosa (s). lie in the submucosa (s).
mgs
mm
me
muscularis externa (me). muscularis externa (me). = = smoothsmooth (sm) & skeletal (sm) & skeletal muscle (sk). muscle (sk).
lymphatic nodules (lymphatic nodules (LL)) are in the mucosa (m). are in the mucosa (m).
L
sub
me
sm
sk
mEsophagus,
middle 1/3rd - med. mag. .
EsophagusEsophagus
The enteric nervous system is extensive and its The enteric nervous system is extensive and its neurons neurons and fibers and fibers form form in thein the submucosa submucosa ((Meissner’s plexusMeissner’s plexus) () (M')M') and in the muscularis and in the muscularis externa (externa (Auerbach’s plexusAuerbach’s plexus) () (A'A').).
M'
A'str.sq.epi
musc. muc.submuc.muscul.
externa.
submucosal gl.
lymphatic nodule
lumen
med
high
high
Esophagus/Stomach junction. -
Epithelium is changed from stratified squamous to
simple columnar (sc).
1
2
3
E
E
S
S
sc
sc
gp
gp
low
med high
Stomach - generalStomach - general
The process of The process of digestiondigestion essentially begins in the stomach; essentially begins in the stomach; little little absorptionabsorption and and excretionexcretion also also occur here.occur here.
The stomach is composed of a mucosa, submucosa, The stomach is composed of a mucosa, submucosa, muscularis externa & serosa. muscularis externa & serosa.
The mucosal lining is a The mucosal lining is a simple columnar simple columnar secretsecretoryory epithelium epithelium (mucous)(mucous). .
Folds (rugae),Folds (rugae), gastric pits gastric pits, mammilated areas., mammilated areas.
GlandsGlands vary in different regions of the stomach. vary in different regions of the stomach.
StomachStomach mucosa:mucosa:
``````epitheliumepithelium
lamina propria:lamina propria: gastricgastric glands ; ;
muscularis mucosae: both muscularis mucosae: both circular and circular and longitudinal longitudinal layerslayers of SM.of SM.
submucosa:submucosa:
muscularis:muscularis: the inner oblique layer, the inner oblique layer, circular layer and longitudinal layer of circular layer and longitudinal layer of SM. SM.
serosa serosa
Stomach, mucosal lining & gastric pitsStomach, mucosal lining & gastric pitsGGastric pits (gp)astric pits (gp) are are invaginations ofinvaginations of a simple columnar a simple columnar
epitheliumepithelium
The mucus blanket which protects the lining from The mucus blanket which protects the lining from stomach acids is present here.stomach acids is present here.
gpsc
Lamina propria contains glandsLamina propria contains glands fundic glandsfundic glands (in the body, fundus) secrete the (in the body, fundus) secrete the
enzymes and acid of the stomach. While enzymes and acid of the stomach. While cardiaccardiac and and pyloricpyloric glands predominantly secrete mucus. glands predominantly secrete mucus.
The fundic glands are simple tubular.The fundic glands are simple tubular.
They contain 4 cell types:They contain 4 cell types:
1. Mucous neck cells1. Mucous neck cells2. Chief cells 2. Chief cells , , or zymogenic cells or zymogenic cells
columnar and basophilic cells - in the columnar and basophilic cells - in the body of the glands. body of the glands.
produce produce pepsinogen and lipasepepsinogen and lipase..
3. 3. Parietal cells
secrete secrete hydrochloric acidhydrochloric acid ( HCL ) and ( HCL ) and intrinsic factorintrinsic factor. . The latter is necessary for The latter is necessary for
absorption of vitamin Babsorption of vitamin B1212 in the ileum in the ileum
4. Enteroendocrine cells (APUD)4. Enteroendocrine cells (APUD)
20 different types20 different types 4 principal hormones:4 principal hormones: Gastrin Hcl secretionGastrin Hcl secretion Secretin, cholecystokinin (CCK), Secretin, cholecystokinin (CCK),
gastric inhibitory peptide (GIP) gastric inhibitory peptide (GIP) pancreatic and gallblader pancreatic and gallblader activity and gastric secretion activity and gastric secretion
Pernicious anemiaPernicious anemia follows the follows the absence of parietal cells (i.e. loss of absence of parietal cells (i.e. loss of epithelium due to gastric ulcer)epithelium due to gastric ulcer)
Disturbance of different cells may call Disturbance of different cells may call the different pathology.the different pathology.
Digestion of different substances Digestion of different substances begins in different regions.begins in different regions.
Fundic Fundic stomachstomach
The lowest mag. shows the mucosaThe lowest mag. shows the mucosa (m)(m), , submucosasubmucosa (sm) with (sm) with folds called rugaefolds called rugae (r) (r)
& the muscularis externa (me). At higher mag. gastric pits (gp)& the muscularis externa (me). At higher mag. gastric pits (gp), , fundic glands (fg), &fundic glands (fg), & muscularis mucosa (mm) comprisemuscularis mucosa (mm) comprisess the the mucosa. Outside is the submucosa (sm) and muscularis mucosa. Outside is the submucosa (sm) and muscularis externa (me). externa (me).
2
m sm
r
me
gp
fg
mmsm
me
low
med
Fundic Fundic stomachstomachmucosamucosa
In fundic stomach,In fundic stomach,
gastric pits occupy gastric pits occupy about 1/about 1/5 5 the the mucosa; fundic mucosa; fundic glands comprise the glands comprise the remaining 3/4ths. remaining 3/4ths.
gastricpit
fundicgland
Isthmus
Neck
Base
Cardiac StomachCardiac Stomach, ,
GGastric pitsastric pits occupy ½ of occupy ½ of mucosamucosa. .
GGastric glands astric glands are simple tubular are simple tubular and slightly branchedand slightly branched
Cells are mucus-secreting andCells are mucus-secreting and
occational endocrineoccational endocrine
gastricpit
cardiacglands
sc
mm
Stomach, pyloricStomach, pyloric
GGastric pitsastric pits occupy 3/4ths the depth of the occupy 3/4ths the depth of the mucosa; the remaining 1/4th mucosa; the remaining 1/4th areare pyloric gland pyloric glands s – short and branched– short and branched. .
The major cell of the gland is the pale mucous The major cell of the gland is the pale mucous (mn); (mn); parietal cells are absentparietal cells are absent as the pyloric as the pyloric stomach nears the intestine.stomach nears the intestine.
gastricpit
gastric gland
mn low
Fundic Stomach, nerve supplyFundic Stomach, nerve supply, , - med & high mag - med & high mag
Elements of the submucosal (s) and myenteric (m) nerve plexuses are Elements of the submucosal (s) and myenteric (m) nerve plexuses are present.present.
fundicglands
musc.mucosa
submucosa muscularisexterna
inner
middle
outer
s
m
smooth muscle
artery
vein