Transcript Document

HISTOLOGY OF THE GIT (ONE)
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GIT COMPOSITION
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Oral Cavity
• The oral cavity is bound by
lips anteriorly and chicks
laterally, and it contains the
tongue and the teeth
supported by periodontium.
• The palate forms its roof
and posteriorly the mouth
communicate
with
the
oropharynx through the
oropharyngeal isthmus
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The lips
• Each lip is lined by skin on the outside and on the inside is lined by
mucous membrane.
• The red free margins of the lips do not contain sweat or sebaceous
glands or hair follicles. These margins of the lips are covered with a
modified skin which represents a transition from skin to mucous membrane.
• Its dermis has numerous blood vessels; as a result the blood in the
capillaries readily shows through the transparent epidermis to make the lips
appear red.
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…the lips
• Internally the lips are covered by a mucous membrane
consists of stratified squamous non-keratinising
epithelium lying upon a connective tissue lamina propria.
The connective tissue that contains small mucous glands
(labial glands) and nerve endings.
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The cheek
• Has an outer covering of skin and inner lining of
mucous membrane, similar to that of the lips. Superficial
cells are constantly being rubbed off the surface and
replaced from below.
• There are small mucous glands in the lamina propria of
the cheek.
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The palate
• The palate is described to have hard palate and soft
palate.
• The hard palate has mucous membranes that covers both
surfaces of the bony skeleton and is firmly attached to it by
a thin layer of dense connective tissue as a result of which
the mucous membrane is not mobile. It is lined by stratified
squamous epithelium, which is keratinized to a variable
degree. A number of mucous glands are present
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…the palate
• The soft palate consists of central skeleton of
dense fibrous tissue (palatine aponeurosis).
• The soft palate has two surfaces, the oral and nasal.
The oral and lower part of the nasal surfaces are
lined by stratified squamous non-keratinized epithelium.
The lining of the rest of the nasal surface is covered by
pseudostratified ciliated columnar epithelium.
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Teeth
• Tooth is hard tissue that fits into the sockets of the
alveolar process of the maxilla and mandible. An
adult has 32 teeth; 16 each jaw and a child has 20
teeth, 10 on each jaw.
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Parts of the tooth
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Tissue component of the tooth
• The tooth has both hard and soft tissue; there are three hard
tissues, the enamel, dentine and cementum and three
soft tissues, the dental pulp, periodontal ligament and
gingiva, that is commonly referred to as gums.
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stellate reticulum
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The gingiva
• Is also known as a gum, it is a dense connective tissue
firmly attached to the underlining periosteum of the
alveolar bone and is lined by mucous membrane, which
is stratified squamous epithelium with patchy
keratinization
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The tongue
• Is a mobile muscular structure that lies in the oral cavity proper.
It consists of intrinsic skeletal muscle covered with mucous
membrane.
• The tongue is made up of the body and the root; the body forms
the anterior two thirds of the tongue while the root forms the
posterior one third. The border between the two is indentified by a
V-shaped furrow known as the sulcus terminalis.
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…the tongue
• The mucous membrane of the ventral surface is stratified
keratinized epithelium and appears smooth.
• The mucous membrane of the dorsal surface of the anterior
two thirds of the tongue is also stratified squamous
epithelium that is partially keratinized in some places but
contain numerous mucosal projections known as lingual
papillae. Because of these mucosal projections the dorsal
surface of the tongue appears rough. However it is not
associated with lingual tonsils.
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The lingual papillae
• There are four types of lingual papilla, these are filiform papilla, fungiform
papilla, folliate papilla and circumvalate papilla
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Filiform papillae
• are the smallest and most numerous papillae. By providing
the tongue with a rough surface they aid in the manipulation
and processing of foods
• The epithelium that forms the filiform papillae is keratinized
and do not contain the taste buds
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Fillform Papilla
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Fungiform papillae
• They occur singly and are fairly evenly spaced between the
filiform papillae. Their connective tissue core is richly
vascularized. The epithelium is slightly thinner than on the
remaining surface of the tongue
• The epithelium at the tip of the papilla contain smaller
number of taste buds and hence play an important role in
appreciation of taste
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Foliate papilla
• These are not well developed in humans and may be absent
in aged individuals.
• If present, they form lamellae along the posterior and
lateral border of the tongue.
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Circumvallate papillae
• These are the largest and least numerous papillae
• They are located along the V-shaped depression, the sulcus
terminalis. Taste buds are particularly numerous on the
lateral surfaces of these papillae.
• They are associated with serous glands (von Ebner
glands) whose ducts open into the trenches surrounding
the papillae and the furrow of the sulcus terminalis.
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Taste Buds
• Taste buds are end organs for taste sensations. They are
barrel shaped and extend throughout the whole thickness of
the epithelium to open to the surface through a minute
gustatory pore. They are composed of three types of cells; the
gustatory cells, sustentacular cells and basal cells.
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Pharynx
• The pharynx is divided into three parts; the Nasopharyx,
Oropharynx, Laryngopharynx). The pharynx has three coats,
an outer fibrous, middle muscular and inner mucous
membrane. The epitheliums is stratified squamous nonkeratinized type
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Tonsils
• In the oropharynx two types of tonsils: the lingual tonsil is located in the
lamina propria in the posterior third or pharyngeal part of the tongue. The
palatine tonsils are pair of tonsils on the lateral wall of the oropharynx
between to arches, the palatoglossal and palatopharyngeal muscles
respectively.
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Waldeyer’s ring
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Salivary Glands
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Salivary Glands
• There are three pairs of large salivary glands they include:
The parotid, Submandibular, and sublingual glands. The function
of these glands is to secrete saliva which enters the oral
cavity via the ducts.
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The parotid glands
• The gland is a compound tubuloalveolar of serous type.
• A dense fibroelastic capsule encloses the gland, which
is part of the investing layer of the deep cervical
fascia.
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The parotid glands
• The parenchyma of the glands consists of secretory end
pieces (the acini) and a branching duct system arranged
in lobes & lobules, separated by septae of connective
tissue originating from the capsule
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… parotid
(histological features)
• The duct system is divided into intralobular and
extralobular ducts.
• The intercalated ducts represent the first duct system and
they originate from the acini. They are lined by simple
cuboidal epithelium. Striated ducts are large ducts in
diameter and are lined by columnar cells that has
microvilli on their apical surface.
• The extralobular ducts are large and include the
excretory ducts and the main duct, the Stensen’s duct
which is lined by stratified columnar cells.
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The submandibular gland
• This is located below the body of the body of the mandible,
its main ducts are known as Wharton’s duct and opens into
floor of the mouth underneath the tip of the tongue.
• It is a compound tubuloalveolar gland with mixed but mainly
serous and few mucous acini.
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…submandibular gland
• The duct system differs from the parotid gland in that it has
short intercalated ducts this makes them less prominent.
• The epithelium of the interlobular ducts is lined by
pseudostratified epithelium with few goblet cells, which
modify the saliva by addition of mucous.
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Sublingual gland
• This is not a single gland but a collection of small groups of
mixed glands, which are predominantly mucous in nature.
It lies in the floor of the mouth over the mylohyoid muscle.
• The main ducts from sublingual glands may open together
with the main duct of the submandibular gland. The duct
system is less prominent because they are short and not
well demonstrated in histological sections.
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Sublingual gland
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