1. LYMPHATIC SYSTEM -2 Learning Objectives
Explain the functions of the spleen.
Describe the structure of splenic pulp, its stroma, and the organization of the parenchyma within the red and white pulp.
Explain the structure of the blood filtration barrier.
Describe the blood circulation of the spleen during closed and open circulation.
Describe the lymphatic circulation of the spleen.
Mimi Jakoi, Ph.D.

2. SPLEEN Secondary lymphoid organ Filter of blood
Removes particulate matter & effete cells
Immune response to blood-borne antigens

3. ORGAN STRUCTURE Capsule, mesothelium & hilus
Parenchyma = small lymphocytes
Divided into red & white pulp
Capsule & mesothelium
White pulp
Red pulp
Hilus
MCP28C

4. CAPSULE, STROMA & SPLENIC PULP
MCP28C_2X
White pulp
Trabeculae
Red pulp
Capsule, trabeculae and stroma = reticular cells & fibers

5. BLOOD FLOW Capsular artery Splenic vein Capsular vein
(hilus)
Splenic artery (hilus)

6. Periarterial Lymphatic Sheath (PALS = T lymphocytes)
WHITE PULP STRUCTURE
2o Nodule = Follicle
(B lymphocytes)
Periarterial Lymphatic Sheath (PALS = T lymphocytes)
Central artery
is eccentric
to the follicle

7. MARGINAL ZONE White Pulp Follicle Red Pulp Entry site for lymphocytes
from blood
Red Pulp

8. BLOOD FLOW Capsular artery Splenic vein Capsular vein
(hilus)
Splenic artery (hilus)

9. RED PULP Cords of Billroth contain reticular cells,
(VM Slide 025)
RED PULP
Cords of Billroth
contain reticular cells,
blood cells and many
macrophages.
Venous Sinus is lined
by littoral cells which
form the filtration
barrier.

10. RED PULP SINUSES Littoral cells line venous sinuses
Endothelial cells line veins
(VM Slide 025)

11. LITTORAL CELLS OF VENOUS SINUS
from Wheater’s Functional Histology
Pore
Diagram of littoral cells
Taken from Ross & Pawlina, Histology A Text and Atlas Lippincott Williams & Wilkins 5th ed.

12. RBC ENTERS VENOUS SINUS
From Tissues and Organs: a text-atlas of scanning microscopy

13. VENOUS SINUSES & TRABECULAR VEIN VS: Venous Sinus T: Trabecular Stroma
TV: Trabecular Vein
Splenic Vein – exit at hilus
from Ross, Kaye & Pawlina, Histology a text and atlas

14. LYMPHATICS EXIT ONLY Efferent lymphatics start
at the marginal zone, exit
along the central artery to
the capsule and out the
hilus.
LYMPHATICS
EXIT ONLY

15. KEY FEATURES OF LYMPHOID ORGANS
Lymph Node Thymus Spleen
Capsule Yes Yes Yes
Cortex-medulla Yes Yes No
Nodule Yes No Yes
Subcapsular sinus Yes No No
Afferent lymphatic Yes No No
Hassall’s Corpuscles No Yes No
Nodule with artery No No Yes
Red and White pulp No No Yes

16. QUESTIONS 1. How do cancer cells enter the spleen in metastasis?
A. From the blood
B. From the lymph
C. Excluded from the spleen always
2. If the spleen is removed, then what organ removes “aged” red blood cells from the circulation?
A. kidney
B. liver
C. lymph node
D. lung