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The Lymphatic System
LAB # 5
1- List the functions of Lymphatic System.2- Describe the exchange of blood plasma, extracellular
fluid, and lymph.3- Describe the structure of a lymph node.4- Explain how the lymphatic system drains into the
vascular system5- Describe the gross anatomy and basic histology of
the spleen.
Functions of the Lymphatic System
1- Lymphocyte Production, Maintenance, and Distribution
2- Collection and Returning of Interstitial Fluid from Tissues to the Circulatory System
3- Distribution of Nutrients, Waste, and Hormones from Tissues to the Circulatory System
1- Lymphocyte Production, Maintenance, and Distribution.
After maturation, most of the lymphocytes move into lymph nodes, the spleen and other lymphoid tissues.
Immature lymphocytes are produced in the bone marrow.
B lymphocytes mature in the bone marrow and T lymphocytes mature in the thymus.
Lymphoid organs and tissues
One function of the lymphatic system is to reabsorb this excess and to return it to the blood.
Fluid continually filters from the blood capillaries into the tissue spaces. But the blood capillaries reabsorb only 85%.
15% (2 – 4 L/day) of the water and about half of the plasma proteins are not absorbed by capillaries.
13 mm Hg
7 mm Hg
2- Collection and Returning of Interstitial Fluid from Tissues to the Circulatory System.
85%
15%
85%
The Lymphatic System
- Lymphatic capillaries
- Lymphatic collecting vessels
- Lymphatic trunks
Aggregates of lymphocytes in the connective tissue of mucous membrane and various organs.
Mucosa-associated lymphatic tissue (MALT)
1- Peyer patches in the distal portion of the small intestine.
They have well –defined anatomical sites and at least partial connective tissue capsules.
2- Thymus
1- Lymph nodes
3- Spleen
It is the recovered fluid. Lymph is usually a clear colorless fluid, similar to blood plasma but low in protein.
Lymphatic Vessels
Diffuse Lymphoid
Tissues
Encapsulated Lymphoid
OrgansLymph
- Collecting duct
3- Tonsils (palatine tonsils and pharyngeal tonsils or adenoids).
2- Vermiform appendix
Lymphoid Organs
Lymphatic Vessels
Lymphoid Tissues
1- Lymphatic Vessels
Pulmonarycircuit
Superior vena cava
Bloodflow
Systemiccircuit
Lymphatic system
Cardiovascular system
The lymphatic capillaries converge to form collecting vessels.
Lymphatic capillaries
Collecting vessels
Lymphatic trunks
Collecting ducts (2)
The collecting vessels converge to form lymphatic trunks.
The lymphatic trunks converge to form collecting ducts.
The collecting vessels travel alongside veins and arteries, and at irregular intervals they empty into lymph nodes. In the lymph nodes, bacteria are phagocytized and immune cells monitor the fluid for foreign antigens.
The names indicates their locations and part of the body they drain1- Jugular trunks, 2- Subclavian trunks, 3- Bronchomediastinal trunks, 4- Intestinal trunk, and 5- Lumbar trunks
1- Right lymphatic duct
2- Thoracic duct
Subclavian veins
Inferior Trunks
Inferior vena cava
3- Lymphatic Trunks and Lymphatic Ducts
Lymph Capillaries
Collecting Vessels
Lymphatic Trunks
Lymphatic Ducts
Right Lumbar Trunk
Left Lumbar Trunk
Intestinal Lumbar Trunk Cisterna Chyli
Thoracic Duct
Right lumbar trunk
Left lumbar trunk
Intestinal trunk
Cisterna Chyli
Thoracic duct
Superior vena cava
Superior Trunks
Right Jugular Trunk
Right Bronchomediastinal Trunk
Right Subclavian Trunk Right Lymphatic Duct
Right Jugular Trunk
Right Subclavian Trunk
Right Bronchome-
diastinal Trunk
Thoracic DuctRight Lymphatic
Duct
RIGHT LEFT Left Jugular Trunk
Left Subclavian
Trunk
Left Bronchome-
diastinal Trunk
Right subclavian vein
Left Subclavian veint
Inferior Trunks
Right Lymphatic Duct Thoracic Duct
Right side of the tissues superior to the diaphragm
Right Lymphatic Duct Thoracic Duct
Tissues inferior to the diaphragm and from left side of the upper body
2- Lymphoid Tissues and Lymph Nodes
Lymphoid Tissues Lymphoid tissues are areolar connective tissues with concentrations of lymphocytes.
The lymphatic nodules or follicles have no fibrous capsule surrounding them.
When lymphocytes are densely packed they form lymphoid or lymphatic nodules or follicles.
Germinal centerIt contains dividing lymphocytes.
Lymphatic nodule or
follicle
It is the collection of lymphoid tissues that protect the epithelia of the respiratory, digestive, urinary, and reproductive systems.
Clusters of lymphoid nodules deep to the epithelial lining of the intestine are known as Peyer’s patches.
MALT (Mucosa-Associated Lymphatic Tissue)
The appendix vermiform is other example of MALT. It walls contain a mass of fused lymphoid nodules.
Tonsils
Functions
They are large concentration of lymphoid nodules in the walls of the pharynx.
Pharyngeal tonsil or adenoid (single)
Palatine tonsils (two)
Lingual tonsils (two)
They guard against ingested or inhaled pathogens.
Lymphatic organs have well-defined anatomical sites and have connective tissue capsule that separates the lymphatic tissue from neighboring tissues.
Lymphoid Organs
- Thymus
- Lymph nodes
- Spleen
Lymph nodes
They are the smallest and most numerous lymphatic organs (about 450 in typical young adult).
Thymus
Spleen
Lymph nodes
They range in diameter from 1 mm to 25 mm (about 1 inch)
Cervical lymph nodes
Axillary lymph nodes
Lumbar lymph nodes
Pelvic lymph nodes
Inguinal lymph nodes
Lymph nodes are wide-spread but specially concentrated in some locations.
Lymph nodes
Lymphvessel
Lymphnodes
Hilum
Medullary sinus
Outer cortex (B cells)
Afferentvessel
Medullary cord(B cells and
plasma cells)Capsule
Dense connective tissue
Deep cortex(T cells)
Subcapsularspace
Medulla
Trabeculae
Efferentvessel
Lymph nodeartery and vein
Lymph nodes are shaped like kidney beans.
Cortex
Lymph Node Functions:
1- They filter and purify the lymph before return to venous circulation (they remove 99% of cell debris, bacteria, viruses, fungi).
2- They provide an early warning system against infection in peripheral tissue, responding before infections reach vital organs of trunk.
3- The first step in immune response takes place in the lymph nodes (extracted antigens are “presented” to lymphocytes).
The Thymus
The thymus is located in the mediastinum.
It atrophies after puberty.
The thymus is divided into two thymic lobes.
Rightlobe
Leftlobe
Septa
Lobule
Septa divide lobes into smaller lobules.Thymus
Lobule
Lobule
The thymus gland LM 50
Cortex
Septa
Medulla
Dividing lymphocyte
s
Maturelymphocyte
s
Lymphocytes
CortexSeptaMedulla
Lobule
Lobule
The thymus gland LM 50A thymic corpuscle LM 550
Reticularcells
Thymiccorpuscle
Mature T cells leave thymus by medullary blood vessels.
T lymphocytes divide in the cortex and mature while they migrate to the medulla.
The thymus secretes thymic hormones that stimulate T cell differentiation.
Spleen
Rib
Pancreas
Aorta
Parietal peritoneum
Visceral peritoneum
Stomach
Diaphragm
Gastric area
Diaphragmatic surface
Renal area
Kidneys
Liver Gastrosplenic ligament
SPLEEN
Hilum
The SpleenIt is the body’s largest lymphatic organ.
The spleen LM 50
White pulp ofsplenic nodule
Capsule
Red pulp
Trabecularartery
Central artery insplenic nodule
White pulp isdominated by lymphocytes.
Red pulp contains a large number of red blood cells.
Functions:1- Removal of abnormal and worn out blood cells.
2- Storage of iron recycled from red blood cells.
3- Initiation of immune responses by B cells and T cells.
Histology of the Spleen
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