Content regarding digestive system

1. By –
Mr ASHOK BISHNOI
Lecturer

2. 2 groups of organs composed of digestive system

4.  It is continuous tube that extends from the
mouth to anus through the thoracic,
abdominal & pelvic cavities.
1.Gastrointestinal tract/ Alimentary canal

5. ◦ Mouth
◦ Pharynx
◦ Esophagus
◦ Stomach
◦ Small intestine
◦ Large intestine
◦ Rectum
◦ Anal canal
◦ Anus

6.  The length of GI tract is about 5-7 meters
(16.5-23 ft) in a living person.
 It is long in Cadaver about 7-9 meters (23-
29.5 ft)

7. Supply secretions contributing to the
breakdown of food
2. Accessory digestive organs

8. ◦ Teeth
◦ Lips
◦ Cheeks
◦ Tongue
◦ Salivary glands (3 pair)
◦ Gallbladder
◦ Liver
◦ Pancreas

9.  Teeth aid in the physical breakdown of food &
tongue assist in chewing & swallowing.
 The other accessory digestive organs never
come in to direct contact with food.
 They produce secretion in the chemical
breakdown of food

10. 1. Ingestion-Taking food in to mouth
2. Secretion- Relies of H2o,acid & enzymes in to lumen of GI tract.
3. Mixing & propulsion
4. Digestion- Mechanical breakdown of food by Mastication
Chemical digestion by Enzymes
5. Absorption- Passage of digested product from the GI tract in to
blood.
6. Defecation- The elimination of faeces from the GI tract
Function of DS;-

12. 12

13. Structure of alimentary canal:-
 The wall of GI tract from the lower oesophagus
to the anal canal.
 It has the “4” layers of tissue
◦ Mucosal layer
◦ Submucosal layer
◦ Muscularis layer
◦ Serosa layer
1.Gastrointestinal tract/ Alimentary canal

15.  It consist of Epithelium Tissue
◦ Stratified squamous (in mouth,
esophagus & anus)
◦ Simple columnar in the rest
Function:-
◦ Protection
◦ Secretion
◦ Absorbtion

16.  Loose connective tissue
◦ containing ,glands and
lymphatic tissue
 Meissner’s plexus
 The secrete:-
◦ Saliva from salivary gland
◦ Gastric juice from gastric gland
◦ Intestinal juice from intestinal gland
◦ Pancreatic juice from pancreas
◦ Bile from liver

17.  Skeletal muscle = voluntary control
◦ in mouth, pharynx , upper esophagus and
anus
◦ control over swallowing and defecation
 Smooth muscle = involuntary control
◦ inner circular fibers & outer longitudinal
fibers
◦ mixes, crushes & propels food along by
peristalsis

18. 4.Serosa:-
• It is outer layer
• Covers all organs and
walls of cavities
• Secretes a serous fluid
• Consists of connective
tissue .

19.  Peritoneum
◦ Cavity within the abdomen
Formed by a
◦ Parietal layer- Which line the abdominal wall
◦ Visceral layer covers organs with in the abdomen & pelvic
cavity
 Peritoneal cavity
◦ potential space containing a bit of serous fluid

20. The path of food:
oral cavity/teeth/salivary glands
oropharynx/epiglottis
oesophagus
stomach
small intestine: duodenum
small intestine: ileum
small intestine: jejunum
large intestine: ascending colon
large intestine: transverse colon
large intestine: descending colon
sigmoid colon rectum anus

21. 21
 It is the main window of
G.I.tract
 From mouth to pharynx
is called oral cavity
 Mouth or oral cavity is
bounded by muscle &
bone.
 Lips- Orbicularis oris
muscle
 Cheeks – Buccinator
muscle
Mouth/Oral cavity:-

24. 24
The vestibule :-is the space
between gums & checks.
The oral cavity:- It is the
space contained within the
upper and lower dental
arches.
Uvula:- Is a carved fold of
muscle covered with mucus
membrane hanging down
from middle palate.

25. 25
Teeth:-
 Called “dentition” (like dentist)
 Teeth live in sockets (alveoli) in the gum-
covered margins of the mandible and maxilla
 Chewing: raising and lowering the mandible
and moving it from side to side while tongue
positions food between teeth

26. 26
 Two sets
1. Temporary/Milk/Primary
/deciduous teeth
1. “Baby” teeth
2. Start at 6 months
3. 20 are out by about 2 years
4. Fall out between 2-6 years
2. Permanent: 32 total
1. All but 3rd set of molars by
end of adolescence
2. 3rd set = “wisdom teeth”
1. Variable
3. Some can be “impacted”
(imbedded in bone)

27. 27
 Incisors: chisel-shaped for
chopping off pieces
 Canines: cone shaped to
tear and pierce
 Premolars (bicuspids) and
 Molars - broad crowns with
4-5 rounded cusps for
grinding
incisor
canine
premolar
molar
Cusps are surface bumps

28. 28

29. 29
 Two main regions
A. Crown (exposed)
B. Root (in socket)
C. Meet at neck
 Enamel
◦ 99% calcium crystals
◦ Hardest substance in
body
 Dentin – bulk of the
tooth (bone-like but
harder than bone,
with collagen and
mineral)
 Pulp cavity with
vessels and nerves
◦ Root canal: the part of
the pulp in the root
A
B
C

30. 30
 Cementum – bone
layer of tooth root
◦ Attaches tooth to
periodontal ligament
 Periodontal ligament
◦ Anchors tooth in boney
socket of the jaw
◦ Continuous with
gingiva (gums)
 Cavities or caries -
rot
 Plaque – film of
sugar, bacteria and
debris
A
B
C

31. 31
 Intrinsic salivary
glands – within
mucosa
◦ Secrete saliva all the
time to keep mouth
moist
 Extrinsic salivary
glands
◦ Paired (2 each)
 Parotid
 Submandibular
 Sublingual
◦ External to mouth
◦ Ducts to mouth
◦ Secrete saliva only right
before or during eating
Saliva: mixture of water, ions, mucus, enzymes
keep mouth moist
dissolves food so can be tasted
moistens food
starts enzymatic digestion
buffers acid
antibacterial and antiviral

32. 32
 Parotids* - largest (think mumps)
◦ Facial nerve branch at risk during surgery here
 Submandibular # - medial surface mandible
 Sublingual + - under tongue; floor of
mouth
Compound = duct branches
Tubo = tubes
Alveolar = sacs
*
#
+

33. 33
 Oropharynx and
laryngopharynx
◦ Stratified squamous
epithelium
 Three constrictor
muscles*
◦ Sequentially squeeze
bolus of food into
esophagus
◦ Are skeletal muscles
 Voluntary action
 Vagus nerve (X)
___oropharynx
___laryngopharynx
*
*
*