Download MBBS Digestive System I Lecture PPT

DIGESTIVE SYSTEM I
INTRODUCTION

? CONSISTS OF TWO GROUPS OF ORGANS

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? 1)GIT or alimentary tract--extend from oral

cavity to anal canal.

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? 2)Accessory digestive organs--these are

teeth, tongue, salivary glands, liver, gall

bladder and pancrease.

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TONGUE

? Accessory digestive organ.
? Composed of skeletal muscle covered with mucous

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membrane.

? Lining mucosa stratified squamous epithelium and

lamina propria.

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? An inverted V-shaped grooved (sulcus terminalis)

divide dorsal aspect of tongue into anterior2/3 and

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posterior 1/3.

? Dorsal aspect of root of tongue contains lingual

tonsil.

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? LINGUAL PAPILLAE
? The anterior 2/3 of dorsal surface is covered with

specialization of epithelium called lingual papillae.

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? Are projection of lamina propria
? Covered with stratified squamous epithelium which

may be keratinized.

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? FOUR TYPES--

i) Filiform

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ii) Fungiform

iii) Circumvallate

iv) Foliate

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? FOLIATE PAPILLAE ARE NOT WELL DEVELOPED IN

HUMAN

? FILIFORM PAPILLAE

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? Cone-shaped
? Mostnumerous
? Anterior2/3ofthetongue.
? Tipsarekeratinized
? No taste Buds

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? FUNGIFORM PAPILLAE
? Mushroomshaped
? Lessnumerous
? Founddistributedamongthefiliformpapillae

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? Has taste buds
? CIRCUMVALLATE PAPILLAE

? 8?16papillaelocated(onav-shapedline)just

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anteriortothesulcusterminalis.

? Largecircularpapillae

? Serousacini(calledVon Ebner's glands)open

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intothegroovetodissolvefoodparticles,sohelp

tasting

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? Hastastebuds
? TASTE BUDS
? Neurosensory epithelial structure embedded in

the surface epithelium of tongue.

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? Also presents in the epiglottis, soft palate and

oropharynx.

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? Onion-shapedstructuresintheepitheliumof

lingualpapillaee.g.fungiformand

circumvallatepapillae.

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? Theirapicalendshasopeningcalledtaste pore

? CELLS IN THE TASTE BUDS--Three types
? i)Neuroepithelial or receptor cells

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? ii)Supporting cells
? iii)Basal or stem cells

? stimulationofthetastecellsleadstothe

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stimulationofgustatorynervefibersand
receivingsweet,salty,bitter,andsour
sensations.

? Muscles of the tongue

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? The core of the tongue striated muscle.

? Muscles fibres arranged in transverse,

longitudinal and vertical bundles.

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? In between the muscle bundle loose

connective tissue, adipose tissue and lingual

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gland are present.

SALIVARY GLANDS

? Major glands

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? Lie completely outside the alimentary tract &

connected to it by an excretory duct.

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? Compound alveolar or tubuloalveolar in type.

? Parotid
? Submandibular
? sublingual.

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? Minor glands

? Small salivary glands situated in the mucous

membrane of:

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? Lip (labial)
? Cheeks (buccal)
? Soft palate (palatine)
? Tongue (lingual)

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Functions of Salivary glands

? Secrete saliva composed of water, mucus,

proteins, salts, salivary amylase (ptyalin),

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immunoglobulins (IgA) & lactoperoxidase.

? Serves to moisten food.

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? Lubricates & moistens oral mucosa and lip.

? Initiates the digestion of carbohydrates.
Basic organization

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? Consists of two components:--
? i) Connective tissue component
? ii) Parenchymal components (duct and acini)

? Connective tissue capsule surrounded parotid and

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submandibular gland.

? Septa divides gland into lobes and lobule.

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? Septa forms a medium through which nerves,

blood vessels and ducts passes.

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Duct system
? Lining epithelium of duct system--

? Intercalated--Cuboidal

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? Striated--Columnar

? Interlobular--Pseudostratified columnar

? Main excretory duct--Stratified cuboidal

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Acinar system
PAROTID GLAND

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? Largest salivary gland.
? Well defined capsule.
? Secretory acini--Purely serous.
? Has abundant myoepithelial (basket) cells.
? Ducts--Interlobular in connective tissue septa

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? Intralobular duct in between acini
? Adipose tissue present between acini and

smaller duct.
Parotid gland

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SUBMANDIBULAR GLAND

? Mixed gland
? Well defined capsule and septa.
? Secretory acini--both serous and mucous.

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? Serous acini are more sometimes
? Mucous acini are capped by a layer of serous cells

called serous demilunes.

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? Ducts--same
Submandibular gland
SUBLINGUAL GLAND

? Mixed salivary gland.

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? No definite capsule.

? Septa divides gland into lobules.

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? Secretory acini-- predominantaly mucous acini.

? Duct--intercalated and striated duct rarely seen
Sublingual gland

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SEROUS

MUCOUS

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SIZE OF SECRETORY END PIECE SMALL

LARGE

SIZE OF LUMEN

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SMALL

LARGE

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SECRETION

THIN WATERY

THIC VISCOUS

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NATURE OF SECRETORY

ZYMOGEN GRANULES

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MUCINOGEN DROPLETS

GRANULES

NUCLEUS

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ROUND, CENTRAL

FLAT , PERIPHERAL

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FUNCTION

ENZYME ACTION

PROTECTION & LUBRICATION

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EXAMPLE

PAROTD GLAND

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SUBLINGUAL GLAND