GIT 1

Dr.Deepak N.Khedekar/LTMMC/NOV/2016 1

DIGESTIVE SYSTEM-1

DR.DEEPAK N.KHEDEKARDEPARTMENT OF ANATOMY

NOV 2016


LIP


LIP• Entry point of the

alimentary canal. • Thin keratinized

epithelium of face skin changes to the thick parakeratinized epithelium of the oral mucosa.


• Skin of the face(Top), the red margin of the lip(middle), and the transition to the oral mucosa (lower).

• Change in thickness of the epithelium from the facial portion of the lip to the interior surface of the oral cavity


KERATINIZED EPITHELIUM-Lip (TOP)H&E ( ×120 )

• Keratinized epithelium (EP) of the face

• Dermis -Hair follicles (HF) , sebaceous glands and arrector pili muscle(Thin skin) BV- venous blood vessels, EP-epithelium,HF-hair

follicle ,M- melanin pigment ,SG-stratum granulosum ,SGl- sebaceous gland arrowheads, connective tissue papillae ,


KERATINIZED EPITHELIUM - LIP (TOP) H&E ( ×380 )

• Reddish brown material in the basal cells- pigment melanin (M)

• Dark blue near the surface- stratum granulosum (SG) with its deep-blue-stained keratohyalin granules.


RED MARGIN H &E × 120



• Keratinized Epithelium of the LIP is much thicker than that of the face.

• Stratum granulosum is present• Coloration of the red margin is due the deep

penetration of the CT papillae into the epithelium (arrowheads).

• Extensive vascularity of the underlying CT , (BV), allows the color of the blood



• Sensitivity of the red margin to stimuli such as light touch is due to the presence of an increased number of sensory receptors.

• Meissner’s corpuscle, (MC) seen in each of the two deep papillae in


MUCOCUTANEOUS JUNCTION, H&E × 120

• Transition from the keratinized red margin to the fairly thick stratified squamous parakeratinized epithelium of the oral mucosa.

• Stratum granulosum suddenly ends.


MUCOCUTANEOUS JUNCTION, H&E × 380

• Beyond the site where the stratum granulosum cells disappear, nuclei are seen in the superficial cells up to the surface(arrows).

• The epithelium is also much thicker at this point

• and remains so throughout the oral cavity.


DEEPER STRUCTURES OF LIP

• Labial glands –tubuloacinar, mucus secreting in deep CT

• Adipose cells• Central core is formed by Skeletal muscle-

orbicularis oris


LIP


TOOTH


TOOTH

• Major component of the oral cavity • Essential for the the digestive process. • Embedded in and attached to the alveolar

processes of the maxilla and mandible. (Gomphosis)

• Children have 10 deciduous (primary, milk) teeth in each jaw, on each side:

• Adult has 32 Permanent (secondary) teeth


TOOTH -HISTOLOGY3 specialized tissues:Enamel,Dentin,CementumParts of the tooth :Crown - Ends at the

neck, or cervix, of the tooth at the cementoenamel jn.

Root -covered by cementum, a bonelike material.


Enamel

• Hard, thin ,translucent layer of acellular mineralized tissue• Covers the crown of the tooth.

Dentin• Most abundant dental tissue • Lies deep to the enamel in the crown and

cementum• Unique tubular structure and biochemical

composition support the more rigid enamel and cementum


CEMENTUM

• Thin, pale-yellowish ,bone like calcified tissue • Covering the dentin of the root of the teeth.• Softer and more permeable than dentin. • Easily removed by abrasion when the root

surface is exposed to the oral environment.


ENAMEL

• Hardest substance in the body; • Consists of 96 to 98% calcium hydroxyapatite.• An acellular mineralized tissue.• Varies in thickness over the crown and may be

as thick as 2.5 mm on the cusps (biting and grinding surfaces) of some teeth.

• Once formed it cannot be replaced. • Unique tissue because, as it is a highly

mineralized material derived from epithelium.


ENAMEL

• Clinical crown-Enamel that is exposed and visible above the gum line

• Aanatomic crown- all of the tooth that is covered by enamel, some of which is below the gum line.


ENAMEL

Enamel rods- • Span the entire thickness of the enamel layer. • Thin structure extending from the Dentino-

Enamel junction to the surface of the enamel. • Where the enamel is thickest, at the tip of the

crown, the rods are longest• Embryology: Produced by ameloblasts


ENAMEL RODS • Rods reveal a keyhole shape.

• Head- upper ballooned part of the rod, oriented superiorly,

• Tail- lower part of the rod, is directed inferiorly.

• Within the head, the enamel crystals are oriented parallel to the long axis of each rod.

• Within the tail, the crystals are oriented more obliquely.


ENAMEL RODS


DENTIN

• Dentin is produced by neural crest–derived odontoblasts of the adjacent mesenchyme.

• Calcified material that forms most of the tooth substance.

• Lies deep to the enamel and cementum.


DENTIN

• Contains less hydroxyapatite than enamel, about 70%, but more than is found in bone and cementum.

• Like ameloblasts, odontoblasts are columnar cells that contain a well-developed rER, a large Golgi apparatus, and other organelles associated with the synthesis and secretion of large amounts of protein


DENTINAL TUBULES

• Apical surface of the odontoblast is in contact with the forming dentin

• Junctional complexes of the odontoblasts separate the dentine from the pulp

• Odontoblast processes embedded in the dentin in narrow channels called dentinal tubules .

• Tubules and processes continue to elongate as the dentin continues to thicken by rhythmic growth.


DENTIN -GROWTH LINES

• Also known as Incremental lines of von Ebner OR thicker lines of Owen

• Produces by Rhythmic growth of dentin produces certain “growth lines” in the dentin

• Mark significant developmental times such as birth (neonatal line)

• Study of growth lines has proved useful in forensic medicine.


CEMENTUM

• Avascular structure ,covers the root of the tooth.• Thin layer of bonelike material• Secreted by cementocytes , cells that closely

resemble osteocytes. • Like bone, cementum is 65% mineral. • Contain Lacunae and canaliculi consist of in the

the cementocytes and their processes,


CEMENTUM• Consist of canaliculi which do not form an

interconnecting network. • A layer of cementoblasts is seen on the outer

surface of the cementum, adjacent to the periodontal ligament.

• Sharpey’s fibers -Collagen fibers that project out of the matrix and embed in the bony matrix of the socket wall form the bulk of the periodontal ligament


CEMENTUM

• Elastic fibers are also a component of the periodontal ligament allowing slight movement of the tooth to occur naturally.

• Forms the basis of various orthodontic procedures

• During corrective tooth movements, the alveolar bone of the socket is resorbed and resynthesized, but the cementum is not.


SHARPEYS FIBRES


DENTAL PULP AND CENTRAL PULP CAVITY(PULP CHAMBER)

• Connective tissue compartment bounded by the tooth dentin.

• Space within a tooth • Occupied by dental pulp, a loose connective

tissue that is richly vascularized and supplied by abundant nerves

• Takes the general shape of the tooth


CENTRAL PULP CAVITY

• Apical foramen- Vessels and nerves enter the pulp cavity at the tip (apex) of the root

• Blood vessels and nerves extend to the crown of the tooth, where they form vascular and neural networks beneath and within the layer of odontoblasts.

• Because dentin continues to be secreted throughout life, the pulp cavity decreases in volume with age.


PULP CAVITY


SUPPORTING TISSUES OF THE TEETH

include…• Alveolar bone• Alveolar processes

of the maxilla and mandible

• Periodontal Ligaments

• Gingiva.


PERIODONTAL LIGAMENT

• Fibrous connective tissue• Joining the tooth to its surrounding bone. • Provides for the following : Tooth attachment (fixation) Tooth support Bone remodeling (during movement of a

tooth)


DRIED SECTION OF TOOTH

Shows following features…• Lines of schreger• Lines of Retzius• Interglobular spaces • Granular layers of Tomes


TONGUE

• Muscular organ projecting into the oral cavity.• Covered with a mucous membrane that • Consists of stratified squamous epithelium,

keratinized in parts • Resting on a loose connective tissue. • Parts : Root &Free part i.e body• Surfaces: Dorsal & Ventral


TONGUE- MUCOSA

• Dorsal surface Mucosa is modified to form three types of papillae:

filiform, fungiform, and circumvallate


TONGUE - PAPILLA

• Circumvallate papillae form a V-shaped row that divides the tongue into a body and a root

• Dorsal surface i.e. the portion anterior to the circumvallate papillae, contains filiform and fungiform papillae.

• Parallel ridges bearing taste buds are found on the sides of the tongue and are particularly evident in infants.


MUSCLES OF THE TONGUE

• Contains both intrinsic and extrinsic voluntary striated muscle.

• Arranged in three interweaving planes, with each arrayed at right angles to the other two.

• Arrangement is unique.• Provides enormous flexibility and precision in

the movements ,essential to human speech as well as to its role in digestion and swallowing.

• Arrangement also allows easy identification.


TONGUEDorsal surface,

H&E ×65; inset ×130


TONGUE, DORSAL SURFACE H&E.

Filiform papillae (Fil P)-• Most numerous of the

three types of papillae. • Conical projections of

the epithelium, with the point of the projection directed posteriorly.

• Do not possess taste buds

• Composed of stratified squamous keratinized E


TONGUE-DORSAL SURFACE, H&E

Fungiform papillae-• Isolated, slightly rounded, elevated structures situated

among the filiform papillae. • Large CT core (primary CT papilla) forms the center of

the fungiform papilla, and smaller CT papillae (secondary CT papillae) project into the base of the surface epithelium

• CT of the papillae is highly vascularized. • Deep penetration of CT into the epithelium,

combined with a very thin keratinized surface, the fungiform papillae appear as small red dots


FUNGIFORM PAPILLA


TONGUE-VENTRAL SURFACE, H&E ×65.

• Smooth surface of the stratified squamous E. (Ep)

• Epithelial surface usually not keratinized.

• CT is deep to the epithelium;

• Deeper still is the striated muscle (M).


TONGUE-VENTRAL SURFACE, H&E ×65.

• CT papillae, project into the base of the epithelium of both surfaces give the epithelial– CT junction an irregular profile.

• CT papillae are cut obliquely

• Appear as small islands of CT within the epithelial layer


TONGUE-VENTRAL SURFACE, H&E ×65

• Muscle (M)- is striated ,fibers travel in three planes.

• Nerves (N) observed in the CT septa between the muscle bundles.

• Surface of the tongue behind the vallate papillae (the root of the tongue) contains lingual tonsils


PAPILLAE AND ASSOCIATED TASTE BUDS

• Foliate, fungiform, and circumvallate, contain taste buds(Tb) in their epithelium.

Fungiform papillae-• Most numerous near the tip of the tongue. • Tb are present in the epithelium on their

dorsal surface.


TASTE BUDS

• Ducts of lingual salivary glands (von Ebner’s glands) empty their serous secretions into the moat surrounding each circumvallate papilla.

• Secretions flush material from the moat to allow the taste buds to respond to new stimuli.

• Taste buds in section appear as oval, pale-staining bodies that extend through the thickness of the epithelium. A small opening at the epithelial surface is called the taste pore.


TASTE BUDS

• Tb in the epithelium covering the circumvallate and foliate papillae are located in deep clefts


• C- cleft CTP, connective tissue papillae D, ducts Ep, epithelium lining the clefts LCT, loose connective tissue LSG, lingual serous glands SE, stratified nonkeratinized epithelium ,TP, taste pore


TASTE BUDS• Oval, pale-staining

structures that extend through much of the thickness of the epithelium.

• BC- Basal cells• NF- nerve fibers • NSC- neuroepithelial

sensory cells • SC- supporting cells• TP- taste pore


TASTE BUDS

• React to only five stimuli: sweet, salty, bitter, sour, and umami.

• Modalities appear to be more concentrated…@ the tip of the tongue- sweet stimuli, @Posterolateral to the tip-salty stimuli, Circumvallate papillae - bitter and umami

stimuli.


TASTE BUDS

Neuroepithelial sensory cells (NSC)- • Cells with the large, round nuclei,most numerous• Possess microvilli @ their apical surface• Form a synapse with the afferent sensory fibers that

make up the underlying nerve.Supporting cells (SC)-Contain microvilli on their apical

surface. Basal cells (BC)- small cells present at base• Stem cells for the supporting and neuroepithelial

cells which have a turnover life of about 10 days


• Portion of the alimentary canal that extends from…

• 1.Proximal part of the esophagus TO

• 2.Distal part of the anal canal

• Hollow tube of varying diameter. Tube has the Same basic structural organization throughout its length.


GITWall is formed by four distinctive layers. 1.Mucosa- consisting of a Lining epithelium, Lamina propria- an underlying connective tissue Muscularis mucosae, composed of smooth muscle2.Submucosa- consisting of dense irregular CT3.Muscularis externa- consisting in layers of

smooth muscle


BASIC LAYERS OF GIT

4.Serosa- a serous membrane consisting of a simple squamous E., the mesothelium, and a small amount of underlying connective tissue.

Adventitia consist of CT is found where the wall of the tube is directly attached or fixed to adjoining structures (i.e., body wall and retroperitoneal organs).


ESOPHAGUSlow-magnification ,H&E


MucosaEpithelium- Nonkeratinized

stratified squamous• Surface cells may exhibit

some keratohyalin granules.

Lamina propria- • Consist of diffuse lymphatic

tissue and lymphatic nodules,

• Proximity to ducts of the esophageal mucous glands


MUCOSA

Muscularis mucosae- • Composed of longitudinally

organized smooth muscle.• Unusually thick in the

proximal portion.Three principal functions of

mucosa: Protection,Absorption, and Secretion


SUBMUCOSA

• Consists of dense irregular CT

• Contains the larger blood and lymphatic vessels, nerve fibers and ganglion cells.

• Nerve fibers and ganglion cells make up the submucosal plexus (Meissner’s plexus).

• Submucosal Glands are also present .


MUSCULARIS EXTERNA• Consists of two muscle layers, an inner circular

layer and an outer longitudinal layer• Differs from the muscularis externa found in

the rest of the digestive tract • Upper one third - striated muscle, a

continuation of the muscle of the pharynx. • Middle third -Striated muscle and smooth

muscle bundles are mixed and interwoven.• Distal third- consists only of smooth muscle, as

in the rest of the digestive tract.


MUSCULARIS EXTERNA

• Nerve plx, the myenteric plx (Auerbach’s plx), is present between the outer and inner muscle layers.

• Plx innervates the muscularis externaAdventitia

• Esophagus is fixed to adjoining structures throughout.• After entering the abdominal cavity, the short

remainder of the tube is covered by serosa, the visceral peritoneum.Mucosal and submucosal glands of the esophagus

secretemucus to lubricate and protect the luminal wall.


ESOPHAGUS


ESOPHAGEAL GLANDS PROPER

• Two types ,both secrete mucus,Esophageal glands proper lie in the submucosa- • Scattered along the length of the esophagus • More concentrated in the upper half. • Small, compound, tubuloalveolar glands• Excretory duct is composed of stratified squamous

epithelium• Mucus produces by it is slightly acidic and serves to

lubricate the luminal wall.


ESOPHAGEAL CARDIAC GLANDS

• Found in the lamina propria of the mucosa. • Present in the terminal part of the esophagus, OR in

the beginning portion of the esophagus.• Produce neutral mucus. • Protect the esophagus from regurgitated gastric

contents. Under certain conditions, however, they are not fully effective,and excessive reflux results in pyrosis, a condition more commonly known as heartburn. may progress to fully developed (GERD).


MUSCLE OF THE ESOPHAGEAL WALL

• Innervated by both autonomic and somatic NS.• Striated musculature in the upper is innervated

the vagus nerve, (from the nucleus ambiguus). • Smooth muscle of the lower part is innervated

by visceral motor neurons of the vagus (from the dorsal motor nucleus).

• Postsynaptic neurons are located in the wall of the esophagus.


ESOPHAGUS-low-magnification ,H&E


THE END

GIT 1

Health & Medicine

Transcript of GIT 1