A&P 2 EXAM 3

UNI with Dr. Bird

Lymphatic system

returns fluids leaked from blood vessels back to blood

Part of the lymphatic system

lymphatic vessels, lymph, lymph nodes

Lymphatic vessels

elaborate network of drainage vessels

Lymph

fluid of the lymphatic system

Lymph nodes

structures that cleanse lymph as it passes through

Lymphoid organs and tissues

structural basis of immune system

List the lymphoid organs and tissue

spleen, thymus, tonsils, lymph nodes

Why is the lymphatic system needed?

hydrostatic and colloid osmotic pressures are not enough to reabsorb everything that exits capillaries, that interstitial fluid needs to be returned

Function of lymphatic vessels

collect the excess protein containing interstitial fluid and return it to blood, transports pathogens to lymph nodes,absorbs fats from intestine to blood

Lympatic capillaries

weave between tissues and blood capillaries, more permeable

Endothelial cell modifications of lymphatic capillaries

minivalves that close when pressure increases INSIDE, anchored to matrix by collagen filaments

Lacteals

specialized set of lymphatic capillaries for absorption and transport of digested fat, inside finger projections of the intestine

Chyle

fatty lymph from the intestines

List the lymphatic vessels by increasing size

capillaries, collecting vessels, trunks, ducts

Collecting lymphatic vessels

have the 3 tunics, travel with superficial veins and deep arteries, largest ones form lymphatic trunks

What are the 9 lymphatic trunks

2 lumbar, 2 bronchomediastinal, 2 subclavian, 2 jugular trunks, 1 intestinal

Name the 2 lymphatic ducts

right lymphatic duct and thoracic duct

Right lymphatic duct

drains right upper limb and right side of head and thorax

thoracic duct

larger, drains everywhere the right lymphatic duct doesn’t, empties into venous circulation at junction of left internal jugular and subclavian veins

Cisterna chyli

an enlarged sac where the thoracic duct starts

Where do large lymphatics receive blood supply?

vasa vasorum

Lymphangitis

when the vasa vasorum feeding large lymphatics become congested during severe inflammation

How do inflamed lymphatics present themselves?

red streaks that are tender to the touch

Are lymphatic vessels high or low pressure, how does it promote unidirectional flow?

low, uses the same structures as veins

Mechanisms that prompt flow through lymphatics

milking action of skeletal muscles

pressure changes in thorax from breathing

pulse pressure from nearby arteries

rhythmic contractions of smooth muscle walls

How does physical activity affect lymph?

increases flow

Lymphedema

insufficient return of lymph to blood resulting in severe localized edema

What can cause lymphedema

tumors blocking lymphatics, surgical removal of lymphatics during cancer surgery

Immune cells found in the lymphatic cells

lymphocytes (T and B), antigen presenting cells, supporting cells

Role of B and T cells

the lymphocytes, protect the body against antigens

List the antigen presenting cells

macrophages and dendritic cells

Macrophages

phagocytize foreign substances and activate T cells

Dendritic cells

capture and deliver antigens to lymph nodes to activate T cells

B lymphocytes

receive the call from antigen presenting cells and identifies issue

T lymphocytes

the general (coordinates cells) and executioner (kills antigens)

What is the supporting cell of the lymphatic system?

reticular cells

Reticular cells

fibroblast like cells that produce reticular fiber stroma in lymphoid organs and tissues

Stroma

network that supports other cell types

What are lymphoid tissue made out of?

reticular connective tissue

Function of lymphoid tissue

houses and provides activiation and proliferation sites for lymphocytes, surveillance location of immune cells

Types of lymphoid tissues

diffuse lymphoid tissue and lymphoid follicules/nodules

Diffuse lymphoid tissue

loose arrangement of lymphoid cells and reticular fibers

Lympoid follicles/nodules

solid, spherical bodies consisting of tightly packed lymphoid cells and reticular fibers

List the 2 functional categories of lymphoid organs

primary and secondary

Primary lymphoid organs

where T and B cells mature

Where do B cells mature?

in red bone marrow

Where do T cells mature?

in the thymus

Secondary lymphoid organs

where lymphocytes are activated

List the secondary lymphoid organs

nodes, spleen, tonsils, peyer’s patches, appendix, diffuse lymphoid tissues

Lymph nodes

clustered along lymphatics, the most important secondary lymphoid organs, imbedded in connective tissue

Protective functions of lymph nodes

cleansing the lymph, immune system activation

Two historical distinct regions of the lymph nodes

cortex and medulla

Cortex of lymph node

superficial part containing densely packed follicles, filled with dividing B cells, deep portion houses T cells in transit, dendritic cells are throughout

Medulla of the lymph nodes

consists of medullary cords, has B, T, and plasma cells

Medullary cords

thin inward extension of cortical tissue

Lymph sinuses

large lymphatic capillaries spanned by crisscrossing reticular fibers, found throughout node

Efferent lymphatic vessels

drain the node, the EXIT

Afferent lymphatic vessels

lead to the node, the entrance

Path of lymph through the lymph nodes

afferent vessels, subcapsular sinus, medullary sinuses, hilium region, efferent vessels

Hilum

indented region on concave side of lymph node

Spleen

blood rich organ, largest lmyphoid organ on left side of abdominal cavity, served by splenic artery and vein

Lymphatic functions of the spleen

stored iron and recycles broken down parts of blood

stores blood platelets and monocytes

site of erythrocyte production

What do monocytes become when they leave the blood?

macrophages

White pulp of spleen

where immune function occurs, mostly lymphocytes on reticular fibers

Red pulp of spleen

old blood cells and pathogens are destroyed, composed of splenic cords that separate splenic sinusoids

Splenic sinusoids

venous sinuses of the spleen

Mucosa associated lymphoid tissue (MALT)

lymphoid tissues in mucous membranes throughout body, lining respiratory/gentitourinary/digestive tracts, protects from pathogens trying to enter body

Largest collections of mucosa associated lymphoid tissue (MALT)

tonsils, peyer’s patches, appendix

Tonils

form ring of lympoid tissue around entrance to pharynx, gather and remove pathogens

List the types of tonsils

2 palatine tonsils, lungual tonsil, pharyngeal tonsil, tubal tonsils

Palatine tonsils

on either side at posterior end of oral cavity

Lingual tonsil

lumpy collection of lympoid follicles at base of tongue

Tubal tonsils

surround openings of auditory tubes into pharynx

Aggregated lymphoid nodules/Peyer’s patches

large clusters of lymphoid follicles in wall or distal portion of small intestine, generate memory lymphocytes

Appendix

tubular offshoot of first part of large intestine that contains large number of lymphoid follicles

prevent bacteria from breaching the intestinal wall

generate memory lymphocytes

Thymus

bilobed lymphoid organ found in inferior neck

extends into mediastinum and partially overlies heart

site of T cell development

When is the thymus development of T cells the most active?

during childhood, after puberty it slows

Parts of thymic lobules

cortex and medulla

Thymic cortex

contains rapidly dividing lymphocytes and scattered macrophages

Thymic medulla

contains fewer lymphocytes than cortex, has thymic corpuscles

Thymic corpuscles

concentric whorls of keratinized epithelial cells, involved in development of regulatory T cells

Regulatory T cells

prevent autoimmune responses, stops activation for self antigents

How does the thymus differ from secondary lymphoid organs?

has no follicles because it lacks B cells

doesn’t directly fight antigens

strictly Tcell maturation

stroma consists of epithelial cells not reticular fibers

How does the thymus keep immature Tcells from getting out?

blood thymus barrier

Immune system

provides resistance to disease causing microorganisms like bacteria, fungi, and viruses, a functional system

***Shared governance

admin and faculty shares decisions about the university

Immunity

resistance to disease

What are the 3 major lines of defense against pathogens?

surface barriers

innate internal defenses

adaptive/specific defense system

Overview of Surface barriers

first line of defense, intact skin and mucosae

Overview of Innate internal defenses

second line of defense, relies on inflammation and internal defenses to inhibit spread of invaders

Overview of Adaptive/specific defense system

3rd line of defense, elite fighting force equipped with proteins to attack and identify enemies, takes longer to mount attack than innate response

List examples of how the innate and adaptive immune systems work together

both release and recognize many of the same defensive molecules, proteins from innate responses alert cells of the adaptive system

Pathogens

harmful or disease causing microbes

Protective mechanism of mucous membranes

form a mechanical barriers that prevents the entry of pathogens (found in any entrance/exit/holes)

Innate immune system cells and responses

phagocytes

natural killer cells

antimicrobial proteins

inflammation

fever

What do innate pattern recognition receptors do?

identify potential pathogens by binding to specific carbohydrates found on them

What pattern recognition receptor plays a central role in triggering immune responses?

toll like receptors (TLRs)

Phagocytes

WBCs that ingest and digest foreign invaders and cellular debris

Neutrophils

most abundant phagocytes in the blood, phagocytize infectious material in tissues, bacterial doomsday

What happens when neutrophils eat too much?

netosis, after eating a lot it will explode to capture any bacteria it couldn’t get so that they can’t leave and other neutrophils can get them