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3. Organs of GIT
Main organs Accessory organs
• Mouth
• Pharynx
• Oesophagus
• Stomach
• Small intestine
• Large intestine
• Rectum
• Anal canal
• Salivary gland
• Liver
• Pancreas
• Gall bladder

4. General structure of the GIT
 The walls of the alimentary tract are formed by four layers
of tissue:
 Adventitia or outer covering (Serous layer)
 Muscle layer
 Submucosal layer
 Mucosa-lining

5. General structure of the GIT

7. General structure of the GIT

8. Adventitia or outer covering (Serous layer)
 In the thorax this consists of loose fibrous tissue.
 In the abdomen the organs are covered by a serous membrane
called peritoneum.
 Peritoneum:
 Is the largest serous membrane of the body.
 Consists of a closed sac, containing a small amount of serous fluid.
 Supplied with blood and lymph vessels & considerable number of lymph
nodes.
 Provides a physical barrier to local spread of infection.
 It has two layers:
 The parietal layer, which lines the anterior abdominal wall
 The visceral layer, which covers the organs (viscera) within the abdominal
and pelvic cavities.

9. The peritoneal cavity , the abdominal organs of the digestive system and the pelvic organs

10. Peritoneum

11. Muscle layer
 Consists of two layers of smooth (involuntary) muscle.
 Muscle fibres of the outer layer are arranged longitudinally
& inner layer encircle the wall of the tube.
 Between these two muscle layers consists blood & lymph
vessels and myenteric plexus.
 Peristalsis mixes food with the digestive juices & onward
movement.
 Onward movement controlled by sphincters consisting of
circular muscle fibres.
 Control allows time for digestion and absorption.

12. Muscle layer

13. Movement of a bolus by peristalsis

14. Submucosa
 Consists of loose connective tissue with some elastic fibres.
 Within this layer are plexuses of blood vessels and nerves,
lymph vessels and varying amounts of lymphoid tissues.
 Blood vessels consist of arterioles and capillaries.
 Nerve plexus is the submucosal or Meissner's plexus.
 It consisting of sympathetic and parasympathetic nerves
which supply the mucosal lining.

15. Mucosa
 This consists of three layers of tissue:
 Mucous membrane: formed by columnar epithelium is the
innermost layer and has three main functions: protection, secretion
and absorption.
 lamina propria: consisting of loose connective tissue, which
supports the blood vessels that nourish the inner epithelial layer,
and varying amounts of lymphoid tissue that has a protective
function.
 Muscularis mucosa: a thin outer layer of smooth muscle that
provides involutions of the mucosa layer, e.g. gastric glands, villi.

16. Mucosa
 Mucous membrane:
 parts of the tract which are subject to great wear and tear or
mechanical injury.
 Consists of stratified squamous epithelium with mucus-
secreting glands.
 Food is soft and moist and where secretion of digestive
juices and absorption occur.
 Consists of columnar epithelial cells with mucus-secreting
goblet cells.

18. Mouth
 Lined with mucous membrane.
 Consist of stratified squamous epithelium.
 Lips:
 Are two fleshy folds that surround the oral orifice.
 Are covered on the outside by skin and are lined on the inside by
mucous membrane.
 Is made up by the orbicularis oris muscle.
 Mouth Cavity
 Mouth extends from the lips to the pharynx.
 Entrance into the pharynx by the palatoglossal fold on each side.
 Mouth is divided into the vestibule and the mouth cavity proper.

19. Cavity of the mouth

20. Mouth
 Vestibule:
 Vestibule lies between the lips and the cheeks externally and the gums and
the teeth internally.
 This slitlike space communicates with the exterior through the oral fissure
between the lips.
 Lateral wall of the vestibule is formed by the cheek.
 Mouth Proper:
 Mouth proper has a roof and a floor.
 Roof of Mouth:
 Roof of the mouth is formed by the hard palate in front and the soft palate
behind.
 Floor of Mouth:
 Floor is formed largely by the anterior two thirds of the tongue and by the
reflection of the mucous membrane from the sides of the tongue to the
gum of the mandible.

23. Mouth
 Tongue:
 Is a voluntary muscular structure which occupies the floor of the mouth.
 Attached by its base to the hyoid bone and by a fold of its mucous
membrane covering, called the frenulum.
 Superior surface consists of stratified squamous epithelium, with
numerous papillae.
 Vallate papillae:
 Usually between 8 and 12 altogether toward the base of the tongue.
 Are the largest of the papillae and are the most easily seen.
 Fungiform papillae:
 Are situated mainly at the tip and the edges of the tongue more numerous
than the vallate papillae.
 Filiform papillae:
 Are the smallest of the three types and most numerous on the surface of
the anterior two-thirds of the tongue.

25. Locations of the papillae of the tongue and related structures

26. Mouth
 Teeth:
 Are embedded in the alveoli or sockets of the alveolar edges of the mandible
and the maxilla.
 Deciduous Teeth:
 Are 20 deciduous teeth: four incisors, two canines, and four molars in each
jaw.
 begin to erupt about 6 months after birth and have all erupted by the end of
2 years.
 Teeth of the lower jaw usually appear before those of the upper jaw.
 Permanent Teeth:
 There are 32 permanent teeth: 4 incisors, 2 canines, 4 premolars, and 6
molars in each jaw.
 Begin to erupt at 6 years of age.
 Last tooth to erupt is the third molar, which may happen between the ages
of 17 and 30.

27. Mouth
 Functions of the teeth:
 Incisor and canine teeth:
 Are the cutting teeth and are used for biting off pieces of food.
 Premolar and molar teeth:
 With broad, flat surfaces, are used for grinding or chewing food.
The shapes of the
permanent teeth.

28. Sagittal section
through the lower jaw
and
gum showing an
erupted temporary
incisor tooth and a
developing
permanent tooth

29. References
 Clinical anatomy: Harolad Ellis
 Human anatomy:BD Chaurasia’s (lower limb & upper
limb)
 Grant’s Atlas (Agur & Dalley, 2002)
 Snell clinical anatomy