Lecture Topic:

Lymphatic

system

One way system: to the heart

Return plasma protein and

excess tissue fluid (2-4 L/day

Lacteals in small intestine

absorb dietary lipids

Recognizes specific foreign

molecules.

Lymphatic system

Lymphatic

system

Cardiovascular

system

Lymphatic system

Lymphatic

Vessels

1).Lymph capillaries

Have one way mini-valves allowing excess fluid to

enter but not leave

Picks up bacteria and viruses as well as proteins,

electrolytes and fluid

Absent in bones, bone marrow, teeth, CNS

2).Lymphatic collecting vessels

Similar to blood vessels (3 layers), but thin &

delicate

Superficial ones in skin travel with superficial veins.

Deep ones ( in trunk and digestive viscera) travel

with deep arteries.

Drain into superficial and deep lymph nodes.

3).Lymphatic Trunks

Lumbar

Intestinal

Receives fatty lymph (chyle) absorbed through lacteals of intestines

Broncho-mediastinal

Subclavian

Jugular

(Paired, except intestinal)

Drain into cisterna chyli

Lymphatic Trunks

Right

Broncho-

Mediastinal

Trunk

Right subclavian trunk

Left

Broncho-

Mediastinal

Trunk

Left subclavian

trunk

Right lumber Trunk Left lumber Trunk

Thoracic Duct

Cisterna Chyli

Right jugular trunk Left jugular trunk

Intestinal Trunk

4).Lymphatic ducts:

Thoracic duct (always present)

(drain into left subclavian vein)

20% also have a right lymphatic duct

(drain into right subclavian vein)

Lymphoid

Organs

Lymph nodes

Spleen

Thymus

Tonsils

Small intestine &

appendix (lymphoid nodules)

Lymphatic system

L

Function of lymph nodes

FILTERING THEM FROM LYMPH TO INITIATE AN

IMMUNE RESPONSE.

DISTROY MOST PATHOGENS

BY

LYMPH NODES ARE FOUND IN

GROUPS

Superficial groups:-Cervical

-Axillary

-Inguinal

Deep groups:-Tracheobronchial

-Aortic

-Iliac

Lymph Nodes Structure

Bean shaped masses of lymphoid tissue( Conn. Tissue & lymphocytes.

Covered by Capsule, gives off trabiculae.

In between trabiculae, Cortical and Medullary sinuses.

Sinuses contain lymph. follicles (nodules)

Follicles are masses of B-Lymphocytes.

Afferent

Lymphatic

vessels

Efferent

Lymphatic

vessel

Nodules (also called follicles)

(Spherical masses of mostly B-lymphocytes).

1. Scattered Lymphatic nodules. (in submucosa of GIT).

2. Aggregated lymphatic nodules. (“Payer's Patches”)

About 40 follicles / 1 cm area.

Distal ileum and Appendix

The thymus

Secrete hormones (thymopoietin, thymulin and

thymosin) for the development of T-lymphocytes

Thymus is the organ where T-cells become

mature and differentiate.

Very large in fetus, after age 14 begins involution

(in elderly mostly fatty and fibrous tissue)

Structure of the thymus

Capsule gives off trabeculae, divides parenchyma into lobules of cortex and medulla

Cortex is darker than the medulla.

Medulla has more mature T-lymphocytes.

Medulla contains Hassall's corpuscles.(Masses of aged, degenerated cells)

Thymus Gland

Structure of the thymus

SPLEEN

This is the largest lymphoid organ,

posterior to the stomach.

SPLEEN STRUCTURE

(spleen is about the size of a fist).

a. Capsule

b. Trabeculae

c. Red pulp

d. White pulp

RED PULP:

(made of sinuosoid capillaries)

WHITE PULP:

(made of masses of lymphocytes)

FUNCTIONS OF THE SPLEEN

Phagocytizes bacteria and other foreign materials : “white pulp”

Removal & destruction of aged or defective blood cells: “red pulp”

Stores platelets

In fetus: hematopoiesis

TONSILS. LOCATION

Palatine tonsils:

pair at posterior margin of oral cavity

most often infected

Lingual tonsils:

pair at root of tongue

Pharyngeal tonsil (adenoid):

STRUCTURE OF PHARYNGEAL TONSILS

Covered by epithelium

Tonsillar crypts

Lymph Nodules (Follicles)

Lymphocytes

Tonsils

Hematopoiesis

thank you for attention.THE END!