Histo Of Git

Front 1

four principle layers

Back 1

mucosa, submucosa, muscularis externa, serosa

Front 2

mucosa

Back 2

 Innermost layer: consists of:
 Epithelium:
- Stratified squamous or simple columnar epithelium
- Permeable barrier
- Produces hormone for digestion and motility of GIT
- Produces mucus for lubrication and protection
 Lamina propria:
- Loose CT rich in blood and lymph vessels; with smooth muscle and lymphoid tissue
 Muscularis mucosae/Interna:
- Very thin layer composed of:
o Inner circular layer
o Outer longitudinal layer
- Function: Moves the mucosa independent of other movements of the GIT  increasing contact time with food for absorption.

Front 3

submucosa

Back 3

 Dense CT with blood and lymph vessels and glands
 Only Esophagus and duodenum have submucosal glands
 Feature: Submucosal plexus or Meissner’s plexus

Front 4

muscularis propria/externa

Back 4

Generally has 2 layers (stomach has 3 layers):
 Inner circular layer
 Outer longitudinal layer
 Feature: Myenteric plexus or Auerbach’s plexus in between the 2 muscular layers
 Function: Moves GIT; propels and mixes the food
 Blood and lymph vessels in the CT between muscle sublayers

Front 5

serosa/adventitia

Back 5

Thin layer of loose CT with adipose tissue covered by mesothelium  simple squamous epithelium
 Serosa: If the organ or segment is located inside the peritoneum (intraperitoneum)
 Adventitia: If the organ or segment is located outside the peritoneum or retroperitoneum; no mesothelium present, only CT
 No serosa in oral cavity

Front 6

hard palate

Back 6

 Lining: Keratinized Stratified Squamous Epithelium (also the lining epithelium for gums and gingival)
 For protection of oral mucosa during mastication; interdigitates with underlying CT
 No muscularis externa and serosa
 Replaced by bone

Front 7

soft palate

Back 7

 Lining: Nonkeratinized Stratified Squamous Epithelium
 Submucosa with numerous small mucous glands
 Core of skeletal muscle, numerous glands and lymphoid nodules in mucosa
 Included are lips, inner cheeks, floor of the mouth
 In the lips, transition from oral nonkeratinized to keratinized of the skin can be observed

Front 8

tongue

Back 8

strongest ms body, base ant wall pharynx,
lining: NK strat. squa epi
Mucus glands at the base of tongue; Serous glands at the body, infront of sulcus terminalis
 Mass of skeletal muscle covered by mucous membrane
 Smooth on ventral surface/lower surface irregular on dorsal surface due to presence of papillae
 Muscle fibers cross one another in 3 planes that is separated by CT: longitudinal, vertical and horizontal
 Sulcus terminalis: separates the posterior 1/3 from anterior 2/3 of dorsal surface

Front 9

small lymphoid aggregations tongue

Back 9

Types of small lymphoid aggregations:
1. Small collection of lymph node
2. Lingual tonsils at posterior 1/3
 Papillae: Small eminences that cover tongue’s dorsal surface, elevation

Front 10

taste buds

Back 10

Onion shape structures, each containing 50-100 cells; buds rest on basal lamina that secretes amorphous material
 Modified columnar cells
 Contains gustatory receptors
 Detect at least 5 broad categories
1. Metal ions: SALT
2. Hydrogen ions from acids: SOUR
3. Sugars, organic compounds: SWEET
4. Alkaloids, toxins: BITTER
5. Contain amino acids: SAVORY/UMAMI
 1st two ions has an ion channel receptor, the next 3 has G-protein receptor
 Hot and spicy foods are perceived by pain receptors

Front 11

components taste buds

Back 11

Components:
1. Neuroepithelial Taste cell: receptors; connected to afferent nerve fiber
2. Supporting cell: sustentacular cells
3. Basal cell: responsible for mitotic activity/replacement of all cell types
4. Taste pores: small opening, for stimulus to come in contact with the taste bud
5. Tastants: substance being release to elicite taste

Front 12

filiform papillae

Back 12

Elongated, conical shape
- Most numerous and are present over the entire dorsal surface of tongue (primarily in rows parallel to sulcus terminalis)
- Facilitates food movement during chewing process
- Feature: Keratinized/Cornified tips and has NO taste buds

Front 13

fungiform papillae

Back 13

Resembles a mushroom; narrow stalk, smooth surface and dilated on the upper portion
- Contains scattered taste buds on upper surface
- Irregularly interspersed among filiform papillae
- Richly vascularized giving reddish color

Front 14

foliate papillae

Back 14

Poorly developed and rarely seen (developed in rodents)
- Maybe found in lateral surface; few and hard to locate
- Consist of two or more parallel ridges and contains many taste buds

Front 15

circumvallate papillae

Back 15

Largest and least numerous; 7-12 circular papillae with flattened surfaces that extend above other papillae(tallest)
- Deep with grooves at the base are openings of Serous/Von Ebner’s glands.
- Distributed in the V-shaped sulcus of the posterior of the tongue; has MANY taste buds on lateral sides of its furrows
- Has two glands: Serous glands and small mucous glands
-

Front 16

serous/von Ebner's glands

Back 16

secretes lipase that prevents formation of hydrophobic layer over the taste buds.
o Flow of secretion washes away food surrounding papillae, so that newly received gustatory stimulus can be processed

Front 17

cemeuntum

Back 17

Produced by cementocytes, encased in lacunae like osteocytes
- Similar in composition to bone except the absence of Haversian system
- Labile and react to stresses to which it is subjected to resorbing old tissue or producing new tissue
- Covers the dentin in root area
- Nourishment comes from periodontal ligament
- Only tissue considered as both basic part of tooth and component of periodontium

Front 18

peridontal ligament

Back 18

Permit limited movement and support during mastication
- Fibers that penetrate the cementum and binds it to bony walls or alveolar bone which permits movement of tooth

Front 19

alveolar bone

Back 19

Immediate contact with periodontal ligament -> serve as periosteum
- Immature bone
- Projects Sharpey’s Fibers: connecting bridge between two structures
- Perforating vessels: penetrate the periodontal ligament
- Many of collagen fiber bundle of periodontal ligament penetrate this bone  bind to cementum

Front 20

parts peridontium

Back 20

cementum, peridontal lig, alveolar bone

Front 21

dentin

Back 21

Calcified tissue that is bulk of the tooth
- Harder than bone due to its higher Calcium content (70% Ca-Hydroxyapatite)
- Other components: Type I collagen fibrils; glycosaminoglycans (secreted by odontoblast), phosphoproteins, and phospholipids.
 Odontoblast: secretes organic matrix that line internal surface of the tooth; produce dentin
 Odontoblast Process/Tome’s Fibers: becomes longer as dentin becomes thicker
 Dental Tubules: extensive branch near the junction between dentin and enamel
 Predentin: unmineralized matrix initially produced by odontoblast
- Sensitive to stimuli: perceived as pain
- Highly innervated, but has few unmyelinated nerve fibers in internal (pulpar) portion

Front 22

enamel

Back 22

Hardest component of the human body
- Inorganic component is mostly hydroxyapatite crystal (96% mineral; 3% water)
- Resist acid dissolution with fluorapatite but no collagens
- Ameloblast: Secretes enamel matrix
 Produced by cells of ectodermal origin
 Organic enamel composed of amelogenins and enamelins
 Consist of enamel rod/prism bounded by interrod enamel
 Prism arrangement is important for enamel’s strength and mechanical property
 Forms a protective epithelium that covers the crown
 Ameloblast process: forms apical extensionwith numerous secretory granules with protein for enamel matrix
 In permanent teeth, ameloblasts are lost, enamel formation not possible

Front 23

pulp

Back 23

Innermost layer; consists of loose CT
- Highly innervated and vascularised  sensitive to pain and the only sensory modality recognized in teeth
- Composed of odontoblast, fibroblast, thin collagen fibrils, ground substance with glycosaminoglycans

Front 24

layers tooth

Back 24

dentin, enamel, pulp, peridontium (cementum, peridontal lig, alveolar bone)

Front 25

gingival sulcus

Back 25

Gingival sulcus: small deepening surrounding the crown, between enamel and epithelium
 Depth of gingival sulcus: important indication of potential periodontal disease

Front 26

gingiva

Back 26

Mucous membrane firmly bound to periosteum of the maxillary and mandibular bones
 Composed of Keratinized Stratified Squamous epith. and lamina propria
 Junctional epithelium: specialized epithelium bound by tooth enamel
 Gingival sulcus:

Front 27

esophagus

Back 27

No digestion
 Muscular tube that serves as a passageway of food from mouth to stomach through peristaltic contractions and relaxation of esophageal sphincters.
 Prevent retrograde flow of gastric contents
 MUCOSA: Lined by Non-keratinized stratified squamous epithelium
o Lamina propria near cardioesophageal junction contains esophageal gastric glands: secrete mucus
 SUBMUCOSA: Has esophageal gland that secrete mucus
MUSCULARIS EXTERNA:
o Proximal segment: Skeletal muscle
o Mid segment: Mixed of skeletal and smooth muscle
o Distal segment: Smooth muscle which makes up the lower esophageal sphincter(LES)
 SEROSA/ADVENTITIA:
o Proximal and mid segment: In thoracic area  adventitia
o Distal: Serosa, because the most distal end is already inside the peritoneum

Front 28

cardioesophageal junction

Back 28

Most distal portion; transition from stratified squamous to simple columnar epithelium (squamocolumnar junction)

Front 29

stomach

Back 29

MUCOSA: presence of RUGAE, folds formed by mucosa and submucosa.
o Lined by simple columnar epithelium
o Surface epithelium forms gastric pits-> where the branched tubular glands of each region empty
o Lamina propria: loose CT with smooth muscle cells and lymphoid nodules
o Presence of muscularis mucosae that separate the mucosa from submucosa
 SUBMUCOSA: dense CT with blood and lymph vessels
 MUSCULARIS EXTERNA: has 3 sublayers
o Outer longitudinal layer
o Middle circular layer
o Inner oblique layer
Pylorus sphincter: Fusion of thick middle layer or circular layer
 SEROSA/ADVENTITIA: Serosa

Front 30

cardia

Back 30

Cardia: Narrow circular region at the transition from esophagus to stomach
 Cardiac glands: SHORT gastric pit; simple branched tubular; terminal portions are LONG coiled with large lumen
 Mucous/secretory cells  Produce mucous and lysozyme to attack the bacterial walls
 Few scattered parietal cells  Secrete H+ and Cl-

Front 31

fundus/body

Back 31

Branched tubular but with less coiling; gastric pit is shorter than gastric gland
 Most of the parietal cells and chief cells are situated in this region

Front 32

pylorus

Back 32

Pyloric glands: deeper lnger gastric pits and shorter coiled gastric glands that also produce mucus and lysozyme
 Gastrin (G) cells: intercalated among the mucous cells; release gastrins which stimulates the secretion of acid by parietal cells
 D cells: secrete somatostatin which inhibits the release of gastrin and other hormones
 Pyloric sphincter: mass of muscle formed by middle circular layer

Front 33

parts gastric glands

Back 33

Isthmus – Near the gastric pit/ foveolae; has mucous cell
2. Neck – Dtem cells, mucous neck cell that is different from the mucous cell in the isthmus, and few parietal cells
3. Base – Composed of parietal cells and chief cells; some neuro or enteroendocrine cells and neck mucous cell

Front 34

neck mucous cell

Back 34

Produces acid mucous (different from surface epithelium mucus) to protect the gastric epithelium from harsh, acid environment of the stomach
- Present in between parietal cells; mucous secretion is different from that of surface epithelium mucous cells
- Basophilic cytoplasm

Front 35

stem cell

Back 35

Low columnar, develop into mature cells when they are needed; seen in the neck of the gland

Front 36

surface epi cells

Back 36

Simple columnar, lies in entire stomach, produce neutral mucus for gastric lining protection

Front 37

cells in gastric glands

Back 37

surface epi cells, stem cell, neck mucous cell, parietal, peptic/chief/ enteroendocrine

Front 38

enteroendorcrine cell

Back 38

Found at the base of foveolae, secrete SEROTONIN, also found in small and large intestines main ducts of liver and pancreas

Front 39

peptic/zymogenic/chief cell

Back 39

Have basophilic cytoplasm (bluish) due to increase of Rough Endoplasmic Reticulum; produce lipase; and an inactive pepsinogen

Front 40

pancreatic/oxyntic cell

Back 40

Mainly in the upper half of the glands (numerous in neck and isthmus); rounded and pyramidal in shape
- Cytoplasm is deeply eosinophilic/acidophilic (pinkish) due to high number of mitochondria
- Single spherical centrally located nucleus
- Produces HCL, potassium and other electrolytes and gastric intrinsic factor (GIF)
- Striking feature of active secretion is: deep circular invagination of apical plasma membrane called intracellular canaliculus (high mitochondria)
- Inactive form  Tubulovesicular structure in apical plasma membrane (few mitochondria)

Front 41

small intestine

Back 41

secretion
 Presence of Plicae circulares (valves of Kerckring), series of folds on the wall(mucosa and submucosa) = increasing surface area by 3x
 Plicae are most developed in proximal jejunum and terminal duodenum
 Villi: Extension/protrusion of mucosa from each plicae (fold of epithelium and lamina propria); increases surface area by 10x
 Microvilli: Apical modification; extension of cell membranes covering cytoplasm; 3000 microvilli for each columnar cell; increasing the surface area by 20x
 Overall increases the surface area by 600x

Front 42

enterocyte

Back 42

Tall columnar cells with brush border packed with microvilli

Front 43

paneth cell

Back 43

Broad base with narrow apex, at the base of intestinal gland; exocrine cells with large eosinophilic secretory granules in their apical cytoplasm that contains lysozyme
 For innate immunity and regulate microenvironment/control of intestinal flora of intestinal crypts

Front 44

microfold M cells

Back 44

Specialized epithelial cells overlying the lymphoid follicles of Peyer’s patches
 Function: endocytose antigens and transport them to the underlying macrophages and lymphoid cells

Front 45

goblet cells

Back 45

Less abundant in duodenum; increases in ileum; protect and lubricate the lining of the intestine

Front 46

small intestine lining

Back 46

MUCOSA: Appearance of plicae circulares
o Lining: simple columnar epithelium with villi
o Glands: Crypts of Lieberkuhn, a simple tubular glands between of villi for renewal of epithelium cell population
o Muscularis mucosae: Bruck’s muscle, strands of smooth muscle extends within core of villus; helps in expelling contents toward mesenteric lymphatic and thoracic duct
Peyer’s Patches: Lymphoid nodules in the lamina propria of some areas of small intestines, mostly seen in the Ileum.
 SUBMUCOSA: Free of glands except in duodenum (presence of glands of Brunner)
 MUSCULARIS EXTERNA: Inner circular layer and outer longitudinal layer with Auerbach’s plexus
 SEROSA/ADVENTITIA: Serosa except Duodenum (retroperitoneum) is covered by adventitia

Front 47

duodenum

Back 47

Has submucosal Brunner’s glands, that protect duodenal luminal surface against the acidity of gastric juice by secreting alkaline mucus bringing intestinal contents to optimum pH for pancreatic enzyme action.
 Clusters of coiled tubular glands that opens into intestinal glands at initial porion of duodenum
 LEAF-like villus
 Line of defense: IgA, intracellular junction and GALT

Front 48

jejunum

Back 48

Prominence of picae circulares
 TALL-SLENDER villus
 Absence of lymphoid tissue; has lymph vessels-plexuses, capillary networks, venules and veins
 Closed tubes at first

Front 49

ileum

Back 49

Prominence of Peyer’s Patches  aggregates of lymphoid nodules; important component of GALT; covering epithelium = M cells
 Lamina propria: rhythmic movement of villus

Front 50

ileo-cecal valve

Back 50

Marks the end of small intestine
- Shows an abrupt change in villous pattern which is found in small intestine mucosa, to the glandular pattern found in colonic mucosa.
- There is also thickening of muscularis mucosa which is smooth muscle tissue found beneath the mucousal layer of digestive tract

Front 51

appendix

Back 51

Narrow irregular lumen; evagination of cecum
 Unlike large intestine, appendix have complete layer of covering (inner circular and outer longitudinal)
 Because in appendix, all taenia coli converge forming a complete covering circumferentially
 Fewer and shorter glands
 Function: participant in immunologic function due to abundant number of lymphoid nodules in the mucosa
 MUCOSA: absence of villi, lined by simple columnar with striated border
 SUBMUCOSA: numerous fat cells and invaded by solitary lymph nodes
 MUSCULARIS EXTERNA: Inner circular and outer longitudinal layer

Front 52

blood circulation in villus

Back 52

Blood vessels penetrate the muscularis externa  forms plexuses in the submucosa  branches in the muscularis mucosae  distributes itself in the villus into a capillary network  capillary network will drain into the veins going to submucosa again  submucosal plexus  penetrate again the muscularis externa  drain into the main venous drainage
- Capiillaries are fenestrated

Front 53

lymph vessel S.I

Back 53

Closes-ended tube in the villus called LACTEALS  Run to the region of lamina propria above the muscularis mucosae for lipid absorption
- Parasympathetic/cholinergic  increases
- Symphathetic/Adrenergic  decreases

Front 54

large intestine

Back 54

Mucosal membrane with no folds, no villi and no plicae except in its distal (rectal) portion; more goblet cells in large than in small intestine
 Intestinal glands are longer in large than small intestine
 No digestive enzymes are secreted
 Contains a large number of bacterial flora
 Functions:
 Absorption of water
 Formation of fecal masss
 Production of mucus for lubrication of hardening fecal material
 MUCOSA: Lined by simple columnar epithelium with striated border
o Lamina propria: Rich in lymphoid tissue (GALT) and related to abundant bacterial population inside the large intestine
 SUBMUCOSA: Same with small intestine
 MUSCULARIS EXTERNA: Inner circular layer and outer longitudinal
o Outer longitudinal layer: Sometimes disappears in some areas because is concentrated to a portion called Taenia coli  Three thick longitudinal bands of fibers if outer longitudinal layer
 SEROSA/ADVENTITIA: Presence of appendices epiploicae, small pendulous protuberance composed of adipose tissue

Front 55

rectum

Back 55

More glands and more cells, lymphoid tissue
 Perianal glands of Gay: large apocrine in region of valves similar to axillary sweat glands
 Rectal/anal sinuses : terminal branches of hemorrhoidal vessels
 Recto-anal junction (squamocolumnar junction)
 Colorectal zone: upper 1/3 lined by simple columnar/glandular epithelium
 Anal transitional zone: stratified squamous epithelium interspersed by columnar cells
 Squamous zone: lower 1/3 lined by nonkeratinized stratified squamous epithelium

Front 56

anal glands

Back 56

Anal glands: extends to submucosa and into the muscularis externa; branched tubular glands that secrete mucus
 Mucosal membrane forms -> rectal columns of Morgagni(anal columns) lined by simple columnar epithelium

Front 57

anus

Back 57

About 2cm above the anal opening – intestinal mucosa is replaced by nonkeratinized stratified squamous epithelium
 Contains a large plexus of veins, which when exclusively dilated and varicosed result into hemorrhoids
 Anal crypts: where circum/perianal glands open
 Muscularis externa: thickens at the level of anal transition zone to form internal anal sphincter (IAS) -> smooth muscles

Front 58

pelvic ms

Back 58

external anal sphincter (EAS)- skeleal

Front 59

cell renewal

Back 59

Continuous through mitotic stem cells
o Stomach: 3-5 days
o Small intestines: every 5-6 days
o Enterocytes, goblet cells: within 6 days
o Enteroendocrine: 4 weeks
 New cells migrate upward until they reach the tip, where apoptotic cells are sloughed off.