A&P Exam 2 (Lymphatic System)

Lymph

Lymph

leaked fluid/plasma proteins, chylomicrons, cell debris/pathogens/cancer cells

How much fluid/plasma proteins is forced out of the capillary bed and into interstitial space daily?

3 liters

Cardiovascular system function

maintain blood volume and retain “energy expensive” blood proteins the liver makes (i.e. albumen)

Chylomicrons

absorbed fat (fatty acids and reformed glycerol) packaged from the small intestine

When does increased uptake of cell debris/pathogen/cancer cells occur and why?

during inflammation because during tissue repair capillaries swell and allow more things to enter

Lymphatic vessels

one way transport toward the heart

Lymph capillaries

microscopic, closed vessels that weave between cells and blood capillaries; more permeable and larger than blood capillaries

Explain the permeable/larger structure of lymph capillaries

cells are not tightly joined (form flap-like mini valves) and collagen filaments anchor cells; pressure of increased interstitial fluid opens gaps in lymphatic walls

Pathway of lymphatics

capillaries → collecting vessels → lymph trunks → lymph ducts

Right lymphatic duct

drains upper right arm and right side of head/thorax

Thoracic duct

drains left side of body above diaphragm and entire body inferior to diaphragm

What do both ducts empty into and what happens to the lymph?

both empty into subclavian veins on respective veins, lymph → plasma

Pathway of fluid from GI to plama

fluid → small intestine → blood/plasma → interstitial fluid → lymph vessels → lymph → subclavian veins → plasma

Lymphatic vessel structure

thinner walls and more valves (one-way) than blood veins, more anastomosis

What is the purpose of one-way valves?

help lymph movement toward heart and prevent backflow

Lymph transport

similar to return through veins: milking action of active skeletal muscles, breathing, pulsations of nearby arteries, and rhythmic contractions of smooth muscle in walls of lymphatic trunks/ducts

When does lymph pooling occur?

when an individual is sedentary for a long period of time

Lymphoid tissue

reticular connective tissue with T and B lymphocytes/macrophages in the spaces of the network

Reticular connective tissue

type of loose connective tissue, forms a network for lymphocytes/macrophages, dominates all lymphoid organs except thymus

T and B lymphocytes

monitor lymphatic stream for presence of antigens and then mound an attack

T cells

reside temporarily before going out to patrol the body; cell mediated response

B cells

clone rapidly when activated by an antigen and release antibodies; can also make antibodies in lymph/blood

Lymph nodes

100s of bean shaped organs less than 1 inch in length that cluster along lymphatic vessels

Regions with lymph nodes

cervical, axillary, inguinal

Lymph node function

filter lymph; have fewer efferent vessels draining than afferent vessels supplying to slow down lymph and allow for lymphocytes/macrophage to work

Spleen

in upper left abdominal cavity below the diaphragm, largest single mass of lymphatic tissue

Functions of the spleen

lymphocytes production/immune response, blood cleansing, and storage/release of platelets

What can result when the spleen is removed?

immunocompetence, increased change for infection

Blood cleansing function of the spleen

macrophages remove pathogens/debris from the blood (occurs in white pulp) and spleen removes defective and old RBCs (occurs in red pulp)

How much of the body’s supply of platelets is stored and released by the spleen?

up to one third

Thymus

site for T cell bootcamp, secretes hormones, only lymphoid organ that doesn’t directly fight antigens

Hormone secretion of the thymus

stimulate T-lymphocytes to become immunocompetent before entrance into lymph nodes, consider endocrine and lymphoid (+bone marrow) organ

Blood-thymus barrier

prevents antigens from coming into premature contact with immature T-cells (prevention of cloning)

Tonsils

swellings around entrance to pharynx

Function of tonsils

gather and remove pathogens entering pharynx from inhaled air and food

Types of tonsils

Palatine (2), pharyngeal (adenoids), and lingual (2)

Which tonsils are largest and most often affected

palatine

Which tonsils are located on the posterior nasopharynx (behind the posterior nasal aperture)?

the pharyngeal (adenoids)

Which tonsils are located at the base of the tongue?

lingual

Two other examples of lymphoid tissue

Peyer’s patches and the appendix

Peyer’s patches

walls of ileum of small intestine

Appendix

offshoot of first part of large intestine

Lymphoid tissue function

protect digestive tract from large amount of pathogens that enter, generate many “memory” lymphocytes for long term immunity

MALT

mucosa associated lymphoid tissue; tonsils/peyer’s patches/appendix is the largest collection