Lymphoid System Part I Flashcards
Functions of Lymphoid System
- drain excess interstitial fluid and return it to the blood. (one way flow to subclavian veins)
- In the small intestine aid in lipid (fat) absorption
- Lymphocytes –> body’s defense against disease causing organisms
Lymphatic Capillaries
found in interstitial spaces of vascular tissue (composed of endothelial cells)
Once fluid enters the lymphatic capillaries is called lymph (fluid connective tissue)
Excess drainage is necessary –> edema
Lacteals
lymphatic capillaries that transport absorbed lipids away from the digestive track
Lymphatic Vessels
merged lymphatic capillaries; similar to veins
Lymphatic Trunks
merged lymphatic vessels; drain larger body regions
Lymphatic Vessels and Trunks are similar to ________.
veins; 3 layers and 1 valve; prevent back flow
Mechanisms for Lymph Movement (similar to venous return)
- skeletal muscle contraction
- Respiratory Pressure Changes
- Intestinal Movements
- Peristaltic Contractions of some Lymphatic Veins
Lymphatic Duct
receive lymph from lymphatic trunks
Right Lymphatic Duct
drains right part of the head and neck; right upper limb and right thoracic region
Right Lymphatic Duct drains to _______.
right subclavian vein
Thoracic Duct
begins at the abdominal cavity as a sac like enlargement _________. Drain left thoracic region, left upper limb, left side of the face and neck and all areas below the diaphragm.
Cisterna Chyli
Sac like enlargement that fives rise to the thoracic duct
Thoracic Duct empties to __________.
left subclavian vein
Primary Lymphoid Organs
- red bone marrow
- thymus
Site where lymphocytes origin
Primary organs; originate from stem cells in the bone marrow.
Types of Lymphocytes
- T cells (migrate after maturation to Thymus)
- B cells (after maturation to bone marrow or lymph nodes)
- Natural Killer Cells
Secondary Lymphoid Organs
- Lymph nodes
- Tonsils
- Spleen
Site where lymphocytes proliferate and immune responses
secondary lymphoid organs
tonsils
small masses of lymphoid tissue, located in the back of the throat, pharyngeal region.
Function of tonsils
- play a role in the immune system’s defense against pathogens, that enter the body through the mouth and nose.
- Initiate immune responses by producing antibodies and activating immune cells such as lymphocytes.
Where is red bone marrow found
spongey bone of axial skeleton and proximal epiphyses of femur and humerus
Red Bone Marrow
site of origin of all formed elements in blood
Immunocompetent
capable of recognizing and attacking a foreign substance; must be able to elicit and immune response.
True or False: every lymphocyte produced by the red bone marrow is immunocompetent
false
B cells become immunocompetent in ______ and T cells mature and become immunocompetent _______ before traveling to secondary lymphoid organs.
red bone marrow and thymus
Thymus
bilobed located above the mediastinum and above the heart.
Why is the thymus large in infants?
large in infants, decreases with age; plays an important role in the development of lymphoid system before birth and during early childhood. Matures after 2 years.
Functions of the thymus
- differentiation of T cells
- produces thymosins
Thymosins
produced by Thymus , promotes T cell differentiation and division, become immunocompetent
Lymph Nodes
occur along larger lymphatic vessels; 1.0 - 2.5 length; site of lymphocyte activation and proliferation.
Location of Lymph Nodes:
- Axillary
- Cervical
- Inguinal
- Thoracic and abdomino- pelvic cavity
True or False: There are lymph nodes in the central nervous system
false
Lymph Nodules
collection of lymphocytes and macrophages within reticular tissue; part of the lymph node structure.
Flow Trajectory through lymph node
- Afferent Lymphatic Vessel: enter
- Lymphatic Sinuses (surround lymph nodules)
- Efferent Lymphatic Vessel: exit
- Hilum
Function of lymph node
cleanse and filter lymph. Trapped particles are destroyed by macrophages and lymphocytes
Lymphocytes remove _______ .
cancerous cells and pathogens
Macrophages remove ______.
cellular debris, dead/ immobile bacteria and viruses.
Spleen
largest lymphoid organ (5-7 cm wide and 13- 16 cm long) found in the left upper quadrant of the abdomino - pelvic cavity. Enveloped by a thin capsule of dense irregular connective tissue, divided into compartments by reticular tissue.
Spleen is a site for ______ .
For proliferation and large venous sinuses.
White Pulp
tissue inside spleen compartment, that has a large number of lymphocytes, concerned with immune responses.
Red Pulp
tissue inside spleen compartment, used to store formed elements. Surrounds white pulp and the venous sinuses ;
site where worn out pathogens and RBC are removed.
Function of spleen in fetus
major blood forming organ
Function of spleen in adults
- cleanse and filter blood, through lymphocytes and macrophages.
- store reserve supply of red blood cells and platelets which can be released in blood in times of need.
- Major site of RBC destruction and recycling
- major site of lymphocyte activation and proliferation
Splenectomy
spleen not essential for life; more susceptible to potential pathogens and the effects of hemorrhage
Tonsils
lymphoid tissue beneath mucous membrane of pharynx and oral cavity.
contain lymphocytes and macrophages
Intercept pathogens that enter through the nose and mouth before entering the blood