Biology Dept. / Comparative Anatomy of Chordates - Seminar

1. University Of SULAIMANI
College Of Science
Department: BIOLOGY
Stomach
Prepared
by:
Peshawa Yasin

2. Index
 Description
 Functions of Stomach
 Shape
 Histology
 Structural anatomy
 Functional anatomy
 Gross Anatomy
 Stomach size
 Gastric emptying
 Mechanical & Chemical Digestion
 Gastrectomy

3. Description
 The stomach is an expanded J-shaped
organ in the upper left region of the abdominal
cavity.
 It is continuous with the esophagus superiorly and
empties into the duodenum of the small intestine
inferiorly.
 It continues the mechanical and chemical
digestion of the bolus. After the bolus has been
completely processed in the stomach, the
product is called chyme.

5. Functions of Stomach
 Digestion.
 Produce acid.
 Reservoir for food.
 Slows food entering intestines.
 Help with vitamin absorption (Vitamin B12).

6. Stomach shape
 Its shape and position are strongly
associated with organogenesis.
 Any developmental abnormality of the
organ itself or nearby located viscera and
peritoneum, as well as their vessels and
nerves may influence stomach
morphology.

7. Stomach Shapes

8. Histology
 The stomach is lined by a simple columnar
epithelium.
 This epithelium contains surface mucous cells
which secrete mucin onto the epithelial lining.
 The muscularis:
 It is composed of three smooth muscle layers instead
of two:
 Inner oblique layer.
 Middle circular layer, and o
 Outer longitudinal layer.

10. Structural anatomy
 The cardia connects the esophagus to the upper
stomach (fundus), which merges with the body
(corpus) followed by the antrum of the stomach.
 The lower outlet of the stomach (pylorus) merges
with the duodenum.
 The left-facing arch of the stomach is the greater
curvature, whereas the right surface forms the
lesser curvature. The superior rounded portion
under the left side of the diaphragm is the
stomach‘s fundus.

13. Functional anatomy
 The stomach can be divided into a proximal
and a distal segment.
 The proximal stomach mainly serves as a
food reservoir. Its tone determines the rate at
which food passes to the distal stomach.
 In the distal stomach, food is further
processed (chyme formation), it is also
responsible for portioning chyme delivery to
the small intestine.

15. Gross Anatomy
 The adult stomach varies from 15 to 25 cm
long, but its diameter and volume depend
on how much food it contains.
 An empty stomach has a volume of about
50 ml and a cross-sectional diameter only
slightly larger than the large intestine, but
when it is really distended it can hold
about 1.5 L of food.

16. Stomach size
 Stomach is the most
dilated part of the
digestive tract.
 Stomach size is
dependent on the
degree of gastric
filling, but this distension
is mainly limited to the
proximal stomach.

17. Gastric emptying
 Solid food remains in the stomach until it has
been broken down into small particles
(diameter of !1mm) and suspended in chyme.
 The chyme then passes to the duodenum.
 The time required for 50% of the ingested
volume to leave the stomach varies, for
instance:
 10—20 min for water and
 1–4 hours for solids (carbohydrates, proteins, fats).

18. When empty, the
stomach collapses
inward, throwing its
mucosa into
large, longitudinal
folds called rugae
(roo’ge).

19. Indigestible substances
 Indigestible substances (bone, fiber, foreign bodies) do not
leave the stomach during the digestive phase.
 Special contraction waves called migrating motor
complexes (MMC) pass through the stomach and small
intestine roughly every 1.5 hours during the ensuing
interdigestive phase, as determined by an intrinsic
―biological clock‖.
 These peristaltic waves transport indigestible substances from
the stomach and bacteria from the small intestine to the
large intestine.

20. Mechanical Digestion
 The walls of stomach have several layers of
smooth muscle. There are three layers of
muscle, when food is present, these muscles
work together to churn the content of
stomach.
 You have probably heard your stomach
―growl‖ when it has been empty for some
times. These sounds are made by the
contraction of smooth muscles that form the
walls of stomach.

21. Chemical Digestion
 Gastric fluid carries out chemical digestion in
the stomach.
 Gastric enzymes:
 Pepsin splits complex protein molecules into
shorter chains of amino acids.
 Hydrochloric acid in the stomach not only
ensure the low pH, but also dissolves minerals
and kills bacteria that enter the stomach
along with food.

22. Gastrectomy
 About half of the patients subjected to total
gastrectomy experience weight loss.
 Malabsorption, particularly fat malabsorption, is
a common feature after total gastrectomy. This
may be due to shortened intestinal transit time
and small bowel bacterial overgrowth, but is less
often due to diarrhea or pancreatic exocrine
insufficiency.

24. Total and subtotal
 In a total gastrectomy, the intestine is
joined to the end of the esophagus,
whilst
 In a partial (or sub-total) gastrectomy the
intestine is joined to the remaining
healthy stomach.

25. sub

26. Total

27. Total and subtotal
 Patients who had a total gastrectomy continued
to suffer from alimentary symptoms, especially
indigestion and diarrhea, during the entire follow-
up period.
 However, patients who underwent subtotal
gastrectomy had a significantly better outcome
already during the first postoperative yr. Patients
given a gastric substitute after gastrectomy
improved with the passage of time and had an
even better outcome in the long run.

28. Common After-Effects of Gastrectomy
 Prolonged period of recovery.
 Reduces size of the food reservoir – this can lead to reduced
food intake and weight loss.
 Vitamin B12 not available from diet – so B12 will be needed by
injection.
 No stomach acid means that the stomach is more susceptible
to infections.
 Rapid movement of food to small intestine – this causes
‗dumping syndrome‘.

34. Comparison between different animals

35. References
 Books
 Elaine N. Marieb, Katja Hoehn. (2013). Human anatomy &
physiology. 9th ed. Pearson Education, Inc. USA. 1107 pp.
 Fox, Stuart Ira. (2011). Human physiology. 12th ed. McGraw-Hill
Companies, Inc. USA. 749 pp.
 Freudenrich c.c. and Tortora G. J. (2010). Visualizing Human
Anatomy and Physiology. John wiley & Sons, Inc. USA 400-415 pp.
 Johnson M.D. (2010). Human Biology Concepts and Currents. 6th
ed. Pearson Education, Inc. 327-341 pp.
 John H. postlethwait, Janet L. Hopson. (2006). Modern Biology.
Holt, Rinehart and Winston. USA. 1130.
 Agamemnon Despopoulos, Stefan Silbernagl. (2003). Color Atlas of
Physiology 5th ed. Georg Thieme Verlag. Germany. 436 pp.

36. References
 Articles:
 Burdan F. and R.K. Ingrid. (2012). Anatomical classification of
the shape and topography of the stomach. 34(2): 171–178
pp.
 Jan Svedlund MD, and Sullivan M. (1999). Long term
consequences of gastrectomy for patients' quality of life: the
impact of reconstructive techniques. 94, 438–445.
 Lars Olbe M.D. and Lars Lundell M.D. (1987). Intestinal function
after total gastrectomy and possible consequences of gastric
replacement. Volume 11, Issue 6, pp 713-719.
 Website:
 http://www.gics.org.uk/content/3.pdf

37. “ THANK
YOU ”