Chapter 20 - The Lymphatic System Flashcards
The Lymphatic System
a system that picks up fluids that have leaked from the vascular system and returns it to the blood. It also plays a role in immunity and removes wastes.
Distribution of Lymph
Lymph is picked up by blind-ended capillaries, and only flows one way, towards the heart.
Endothelial Cells
In the walls of the lymphatic capillaries that have edges that overlap with minivalves to prevent backflow of fluid.
Bundles of Filaments
They anchor endothelial cells to surrounding structures
Lacteals
Highly specialized lymphatic capillaries found on the villi of the intestines. They transport absorbed fat.
Interstitial Space
Lymphatic system helps maintain a fluid balance in the interstitial space
2 Large Ducts
- right lymphatic duct: drains from the right upper arm, right side of the head and thorax.
- thoracic duct: drains from the rest of the body
Lymph Transport
The same mechanism as with the veins. A “milking” due to muscular mechanisms and pressure changes.
Lymph Nodes
Small organs associated with the lymphatic vessels. They’re formed in large clusters. Found in the inguinal, cervical, and axillary regions.
Function of Lymph Nodes
To filter lymph. They have macrophages that remove debris and pathogens, and lymphocytes which form the “early warning” system
Structure of Lymph Nodes
- Cortex - follicles of lymphocytes. Full of transitory T-cells with a germinal center full of B-cells.
- Medulla - Inner area with a large concentration of macrophages
Circulation of Lymph Nodes
Lymph enters the node through the afferent lymph vessels, it moves from the cortex to the medullary sinus, and exits through the efferent vessels towards the heart.
Other Lymphoid Organs
All of them have reticular connective tissue. Their main function is protection of the body.
Spleen Location
On the left side of the abdominal cavity, beneath the diaphragm. It is the largest lymphatic organ.
2 Histological Areas
White pulp - has mostly lymphocytes (WBCs) and macrophages
Red pulp - has mostly erythrocytes (RBCs) and macrophages.
Function of the Spleen
- It removes old and defective blood cells
- It filters blood, removed bacteria and wastes
- In embryo it is a site of erythropoiesis
- It stores platelets and iron
- Site of lymphocyte proliferation and immune surveillance
Thymus Gland
Works by secreting hormones. T-lymphocyte production happens here, and here they become immunocompetent. Size of the thymus increases around puberty to adolescence and then growth stops, after age 20, it starts decreasing in size.
Thymus Cortex
It maintains the blood-thymus barrier. Because T-cells mature in the thymus, it is important to keep them from being contaminated by the external environment.
Tonsils
Rings of lymphatic tissue.
- Palatine: Paired, located on either side of the posterior end of the oral cavity.
- Lingual: Located on the base of the tongue
- Pharyngeal: Located on the posterior superior wall of the nasopharynx
Peyer’s Patches
Clusters of lymph nodules found in the walls of the distal portion of the small intestine. Have macrophages that destroy bacteria. Along with the tonsils, they protect the upper respiratory and digestive tract.
MALT or GALT
GALT - Gut Associated Lymphatic Tissue
MALT - Mucus Associated Lymphatic Tissue
Elephantiasis
The lymphatics become clogged with parasitic worms
Hodgkins Disease
Lymph node malignancy or cancer
