Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Latest Digestive System I Lecture PPT
DIGESTIVE SYSTEM I
INTRODUCTION
? CONSISTS OF TWO GROUPS OF ORGANS
? 1)GIT or alimentary tract--extend from oral
cavity to anal canal.
? 2)Accessory digestive organs--these are
teeth, tongue, salivary glands, liver, gall
bladder and pancrease.
TONGUE
? Accessory digestive organ.
? Composed of skeletal muscle covered with mucous
membrane.
? Lining mucosa stratified squamous epithelium and
lamina propria.
? An inverted V-shaped grooved (sulcus terminalis)
divide dorsal aspect of tongue into anterior2/3 and
posterior 1/3.
? Dorsal aspect of root of tongue contains lingual
tonsil.
? LINGUAL PAPILLAE
? The anterior 2/3 of dorsal surface is covered with
specialization of epithelium called lingual papillae.
? Are projection of lamina propria
? Covered with stratified squamous epithelium which
may be keratinized.
? FOUR TYPES--
i) Filiform
ii) Fungiform
iii) Circumvallate
iv) Foliate
? FOLIATE PAPILLAE ARE NOT WELL DEVELOPED IN
HUMAN
? FILIFORM PAPILLAE
? Cone-shaped
? Mostnumerous
? Anterior2/3ofthetongue.
? Tipsarekeratinized
? No taste Buds
? FUNGIFORM PAPILLAE
? Mushroomshaped
? Lessnumerous
? Founddistributedamongthefiliformpapillae
? Has taste buds
? CIRCUMVALLATE PAPILLAE
? 8?16papillaelocated(onav-shapedline)just
anteriortothesulcusterminalis.
? Largecircularpapillae
? Serousacini(calledVon Ebner's glands)open
intothegroovetodissolvefoodparticles,sohelp
tasting
? Hastastebuds
? TASTE BUDS
? Neurosensory epithelial structure embedded in
the surface epithelium of tongue.
? Also presents in the epiglottis, soft palate and
oropharynx.
? Onion-shapedstructuresintheepitheliumof
lingualpapillaee.g.fungiformand
circumvallatepapillae.
? Theirapicalendshasopeningcalledtaste pore
? CELLS IN THE TASTE BUDS--Three types
? i)Neuroepithelial or receptor cells
? ii)Supporting cells
? iii)Basal or stem cells
? stimulationofthetastecellsleadstothe
stimulationofgustatorynervefibersand
receivingsweet,salty,bitter,andsour
sensations.
? Muscles of the tongue
? The core of the tongue striated muscle.
? Muscles fibres arranged in transverse,
longitudinal and vertical bundles.
? In between the muscle bundle loose
connective tissue, adipose tissue and lingual
gland are present.
SALIVARY GLANDS
? Major glands
? Lie completely outside the alimentary tract &
connected to it by an excretory duct.
? Compound alveolar or tubuloalveolar in type.
? Parotid
? Submandibular
? sublingual.
? Minor glands
? Small salivary glands situated in the mucous
membrane of:
? Lip (labial)
? Cheeks (buccal)
? Soft palate (palatine)
? Tongue (lingual)
Functions of Salivary glands
? Secrete saliva composed of water, mucus,
proteins, salts, salivary amylase (ptyalin),
immunoglobulins (IgA) & lactoperoxidase.
? Serves to moisten food.
? Lubricates & moistens oral mucosa and lip.
? Initiates the digestion of carbohydrates.
Basic organization
? Consists of two components:--
? i) Connective tissue component
? ii) Parenchymal components (duct and acini)
? Connective tissue capsule surrounded parotid and
submandibular gland.
? Septa divides gland into lobes and lobule.
? Septa forms a medium through which nerves,
blood vessels and ducts passes.
Duct system
? Lining epithelium of duct system--
? Intercalated--Cuboidal
? Striated--Columnar
? Interlobular--Pseudostratified columnar
? Main excretory duct--Stratified cuboidal
Acinar system
PAROTID GLAND
? Largest salivary gland.
? Well defined capsule.
? Secretory acini--Purely serous.
? Has abundant myoepithelial (basket) cells.
? Ducts--Interlobular in connective tissue septa
? Intralobular duct in between acini
? Adipose tissue present between acini and
smaller duct.
Parotid gland
SUBMANDIBULAR GLAND
? Mixed gland
? Well defined capsule and septa.
? Secretory acini--both serous and mucous.
? Serous acini are more sometimes
? Mucous acini are capped by a layer of serous cells
called serous demilunes.
? Ducts--same
Submandibular gland
SUBLINGUAL GLAND
? Mixed salivary gland.
? No definite capsule.
? Septa divides gland into lobules.
? Secretory acini-- predominantaly mucous acini.
? Duct--intercalated and striated duct rarely seen
Sublingual gland
SEROUS
MUCOUS
SIZE OF SECRETORY END PIECE SMALL
LARGE
SIZE OF LUMEN
SMALL
LARGE
SECRETION
THIN WATERY
THIC VISCOUS
NATURE OF SECRETORY
ZYMOGEN GRANULES
MUCINOGEN DROPLETS
GRANULES
NUCLEUS
ROUND, CENTRAL
FLAT , PERIPHERAL
FUNCTION
ENZYME ACTION
PROTECTION & LUBRICATION
EXAMPLE
PAROTD GLAND
SUBLINGUAL GLAND
This post was last modified on 30 November 2021