Lecture notes for medical students

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2. Introduction & History.

3. Introduction & History.
• The spleen is a shoe shaped organ located
in the left hypochondrium and partly in the
epigastrium.
• Situated between the fundus of the stomach
and the diaphragm.
• The spleen is very vascular and reddish
purple in color;
• A healthy spleen is not palpable.

4. History

5. History
• The spleen was thought to influence
personality, mood and thought.
• Remove black bile from blood.
• Only in last 100 years its role in
hematopoiesis, immunity is realised.

6. Embryology

7. Embryology
• The spleen develops in the cephalic part of
dorsal mesogastrium (from its left layer)
during the sixth week of intrauterine life).
• Starts with number of nodules that fuse and
form a lobulated spleen.
• Notching of the superior border of the adult
spleen is evidence of its multiple origin

8. Ends

9. Ends
• 2 ends -anterior and posterior end.
• The anterior end of the spleen is expanded
and is more like a border; it is directed
forward and downward to reach the
midaxillary line.
• The posterior end is rounded and is directed
upward and backward; it rests on the upper
pole of the left kidney.

10. Size and Weight

11. Size and Weight
• 75-150 g
• 5-6cm x12-15cm
• Diagnostic imaging to assess spleen size is
routinely accomplished by ultrasonographic
measurement along its long axis. However,
there is variation among radiological texts
in defining the upper limits of normal for
longitudinal diameter, with values ranging
from 12 to 14 cm in adults.

12. Surfaces

13. Surfaces
• 2 surfaces-diaphragmatic and visceral.
• The diaphragmatic surface is smooth and
convex,
• The visceral surface is irregular and
concave and has impressions.
• Hilum is on the inferomedial part of the
gastric impression .
• The hilum transmits the splenic vessels and
nerves and provides attachment to the
gastrosplenic and splenorenal (lienorenal)
ligaments.

14. Relations

15. Relations
• The visceral surface of the spleen contacts
the following organs:
• Anterior surface of the left Kidney.
• Splenic flexure of the colon
• The fundus of the stomach
• Tail of the Pancreas.
• The diaphragmatic surface is related to the
diaphragm; the diaphragm separates the
spleen from the pleura and the lung.

16. Visceral Surface:Impressions.

17. Visceral Surface:Impressions.

18. Borders

19. Borders
• 3 borders
1. superior,
2. inferior,
3. intermediate.
• The superior border of the spleen is notched
by the anterior end.
• The inferior border is rounded.
• The intermediate border directs toward the
right.

20. Arterial Supply

21. Arterial Supply
• The splenic artery -the largest branch of the celiac
trunk .
• Passing through the splenorenal ligament.
• It divides into multiple branches at the hilum.
• The spleen has superior and inferior vascular
segments based on the blood supply.
• The 2 segments are separated by an avascular
plane.
• Its terminal branches aside, the splenic artery also
gives off branches to the pancreas, 5-7 short
gastric branches, and the left gastro-omental
(gastroepiploic) artery

22. Splenic Artery
•

23. Splenic Artery
•

24. Venous Drainage

25. Venous Drainage
The splenic vein
• Forms at the hilum.
• Runs behind the pancreas
• Joins Superior mesenteric vein behind the
neck of the pancreas to form the portal vein.
• Tributaries-
1. The short gastric
2. left gastro-epiploiic
3. Pancreatic
4. Inferior mesenteric veins.

26. Venous Drainage

27. Venous Drainage

28. Lymphatic Drainage

29. Lymphatic Drainage
• Proper splenic tissue has no lymphatics;
however, some arise from the capsule and
trabeculae and drain to the
pancreaticosplenic lymph nodes.

30. Nerve supply

31. Nerve supply
• Sympathetic supply is from Celiac
Plexus.
• There is no parasympatetic supply.

32. Peritoneal Attachments

33. Peritoneal Attachments
• The spleen is surrounded by
peritoneum and is suspended by
multiple ligaments:-
1. The gastrosplenic ligament
2. The splenorenal ligament
3. The phrenicocolic ligament .

34. Peritoneal Attachments
1. The gastrosplenic ligament extends from
the hilum of the spleen to the greater
curvature of the stomach; it contains short
gastric vessels and associated lymphatics
and sympathetic nerves.
2. The splenorenal ligament extends from
the hilum of the spleen to the anterior
surface of the left kidney; it contains the
tail of the pancreas and splenic vessels.

35. Peritoneal Attachments
• 3. The phrenicocolic ligament is a
horizontal fold of peritoneum that extends
from the splenic flexure of the colon to the
diaphragm along the midaxillary line; it
forms the upper end of the left paracolic
gutter.

36. Surface Marking

37. Surface Marking
• The spleen is marked on the left side of the
back with the long axis of the 10th rib.
• The upper border is marked along the upper
border of the ninth rib;
• the lower border, along the 11th rib.
• The medial end lies 5 cm from the midline.
• The lateral extension ends at the midaxillary
line.

38. Microscopic Anatomy

39. Microscopic Anatomy
The spleen has4 components:-
1. Supporting tissue
2. White pulp
3. Red pulp
4. Vascular system

40. Microscopic Anatomy
1. Supporting tissue is fibroelastic and
forms the capsule, coarse trabeculae, and a
fine reticulum.
2. The white pulp consists of lymphatic
nodules, which are arranged around an
eccentric arteriole called the Malpighian
corpuscle.

41. Microscopic Anatomy
3. The red pulp is formed by a collection of
cells in the interstices of the reticulum, in
between the sinusoids.
• The cell population includes all types of
lymphocytes, blood cells, and fixed and
free macrophages.
• The lymphocytes are freely transformed
into plasma cells, which can produce large
amounts of antibodies and
immunoglobulins

42. Microscopic Anatomy
4. The vascular system traverses the spleen
and permeates it

43. Congenital Anomalies

44. Congenital Anomalies
• Accessory spleens or splenunculi -nodules
that fail to fuse during development.
– Found in 18.8%
– In gastrosplenic ligament, splenorenal ligament,
gastrophrenic ligament, and gastrocolic
ligament.
– Rarely broad ligament of the uterus and in the
spermatic cord.
– May grow if spleen is removed.
• Asplenia is a rare condition in which
a congenital absence of the spleen occurs.

45. Physiology

46. Physiology
Functions of Spleen
1. Immune responses
2. Phagocytosis
3. Hematopoiesis
4. Storage of red blood cells.

47. Hematopoiesis

48. Hematopoiesis
• The spleen is an important
hematopoietic organ during fetal life.
• Lymphopoiesis continues throughout
life. The manufactured lymphocytes
take part in immune responses of the
body.
• In the adult spleen, hematopoiesis can
restart in certain diseases such as
chronic myeloid leukemia and
myelosclerosis.

49. Immune responses

50. Immune responses
• After antigenic stimulation
• increased formation of plasma cells for humoral
responses
• increased lymphopoiesis for cellular responses
occurs.
• It processes encapsulated bacteria
• Streptococcus pneumoniae, Haemophilus
influenzae type B and Neisseria meningitidis
types A and C.
• About 0.5 percent of people who have their
spleens removed develop overwhelming post-
splenectomy infection (OPSI)

51. Phagocytosis

52. Phagocytosis
Spleen filters the blood
• Phagocytes in the spleen remove-
• debris
• old and effete red blood cells (RBCs)
• other blood cells
• Microorganisms
• Phagocytosis of circulating antigens
initiates the humoral and cellular
immune responses

53. Storage of RBCs

54. Storage of RBCs
• Approximately 8% of the circulating RBCs
are present within the spleen; however, this
function is seen better in animals than
humans.
• As much as 25% of the circulating platelets
are estimated to be held in reserve in the
spleen

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