PREFINAL: IMMUNE SYSTEM AND LYMPHOID ORGANS Flashcards
IMMUNE SYSTEM & LYMPHOID ORGANS
- Consists of 2 semi-independent parts:
Lymphatic vessels
Lymphoid tissues & organs
Lymphoid tissues & organs 2 types
Primary Lymphoid Organs
Secondary Lymphoid Organs
B lymphocytes and T lymphocytes
Primary Lymphoid Organs
Spleen, Lymph nodes, and Mucosal-associated lymphoid tissues (MALT)
Secondary Lymphoid Organs
o Transport fluids back to the blood.
o play essential roles in body defense and disease resistance.
o Provides defense or immunity against foreign antigens inside the body.
IMMUNE SYSTEM & LYMPHOID ORGANS
Russian scientist who discovered and observed phagocytosis (cells
that eat cells) under the microscope.
ELLIE METCHNIKOFF
serum proteins produced by certain lymphocytes when exposed to a certain substance.
ANTIBODIES
PRIMARY LYMPHOID ORGANS:
Bone Marrow
Thymus
One of the largest tissues in the body and fills the core of all long flat bones.
Bone Marrow
Main source of HSC (erythrocytes, granulocytes, monocytes,
platelets, and lymphocytes)
bone Marrow
Small, flat, bilobed organ found in the thorax, or chest cavity, right
below the thyroid gland and overlying the heart.
Thymus
Thymus weight by puberty?
30 to 40 g
Produces enough young t lymphocytes early in life.
Thymus
Maturation of T cells:
3 weeks
Mature T cells released from the
medulla
Functions at peak levels only during ________ & produces hormones (like thymosin) to program lymphocytes.
childhood
form in the thymus upon interacting with dendritic cells presenting self-antigens in a process promoted by cytokines from thymic epithelial cell (TEC) aggregates called Hassall
corpuscles, found only in the thymic medulla.
Regulatory T cells
After maturation of T cells, they make their way to secondary lymphoid
organs.
- Main contact with foreign antigens takes place.
SECONDARY LYMPHOID ORGANS
largest lymphatic vessel in the body.
• Collects most of the body’s lymph fluid and empties it into the left subclavian vein.
THORACIC DUCT
Making of lymphocytes which occurs in secondary lymphoid organs and
is dependent on antigenic stimulation.
LYMPHOPOESIS
Largest secondary lymphoid organ.
spleen
Located in the upper-left quadrant of the abdomen below the diaphragm.
spleen
Large discriminating filler that removes old and damaged cells and foreign antigens from the blood.
spleen
Spleen receives blood vol. _______ and allows lymphocytes and macrophages to constantly survey for infectious agents
approx. 350 mL/minute
lined by unusual endothelial cells called “stave cells”
SPLENIC SINUSOIDS
elongated and aligned parallel to blood flow with open slits between the cells.
STAVE CELLS
2 types of spleen
red pulp
white pulp
Filters blood, removes defective erythrocytes, and recycles hemoglobin iron, consists of splenic cords with macrophages and blood cells of all kinds and splenic sinusoids.
red pulp
Blood flow in red pulp is either a
close circulation or open circulation
CLOSE CIRCULATION, moving from
capillaries into the
venous sinusoids
OPEN CIRCULATION, capillaries
open directly into
splenic cords
only 20% of the spleen, is a secondary lymphoid tissue associated with small central arterioles that are also enclosed by PALS (periarteriolar lymphoid sheaths) of T cells.
white pulp
contains mainly T-cells.
Periarteriolar lymphoid sheath (PALS)
contain B cells that are not yet stimulated by antigens.
Primary follicles
Kidney-shaped, <1inch long & covered by a capsule of dense connective
tissue. Located along lymphatic ducts, numerous near joints, and where the arms and legs join the body.
LYMPH NODES
o Provide the ideal environment for contact with foreign antigens that
penetrate the tissues.
o Filtration of interstitial fluid from around cells in the tissues,
it allows contact between lymphocytes and foreign antigens
from the tissues.
o Filters lymph and provides a site for B-cell activation and
differentiation to antibody-secreting plasma cells.
o Provide the ideal environment for contact with foreign
antigens that penetrate the tissues
LYMPH NODES
fluid that surrounds cells & tissues.
INTERSTITIAL FLUID
filtrate of blood and arises from the passage of water and into the interstitial spaces between cells.
LYMPH FLUID
2 types of lymphatic vessels
lymph capillaries
lymphatic vessels
Walls overlap to form flap-like mini valves & fluid leaks
into them.
▪ Higher pressure on the inside closes mini valves.
lymph capillaries
Collects lymph from lymph capillaries & carries lymph to
& away from lymph nodes.
• Returns fluid to circulatory veins near the heart.
Lymphatic collecting vessels/Lymphatic vessels
ideal location for phagocytosis
sinuses
consist of antigen-stimulated proliferating B cells
secondary follicles
transformation of B cells takes place.
Germinal center
outer part, contains follicles (collections of lymphocytes).
cortex
location of T-cells in lymph nodes.
paracortex
inner part, contains phagocytic macrophages.
medulla
defense cells
macrophages
lymphocytes
engulf and destroy foreign substances.
macrophages
provide immune response to antigens.
lymphocytes
- Found in gastrointestinal, respiratory, and urogenital tracts. - One of the largest lymphoid organs (70%) - Ex. Tonsils, appendix, and urogenital tracts, and Peyer patches (a specialized type of MALT located at lower ileum of t h e intestinal tract)
MUCOSA-ASSOCIATED LYMPHATIC TISSUE (MALT)
- Found in gastrointestinal, respiratory, and urogenital tracts. - One of the largest lymphoid organs (70%) - Ex. Tonsils, appendix, and urogenital tracts, and Peyer patches (a specialized type of MALT located at lower ileum of t h e intestinal tract)
MUCOSA-ASSOCIATED LYMPHATIC TISSUE (MALT)
Location: Small masses of lymphoid tissue around the pharynx
▪ Trap & remove bacteria & other foreign materials
Tonsil
located posteriorly on the soft palate, are covered by stratified squamous epithelium.
▪ The surface area of each is enlarged with 10-20 deep invaginations or tonsillar crypts in which th
Palatine tonsil
are situated along the base of the tongue, are also covered by stratified squamous epithelium with crypts, and have many of the same features as palatine tonsils but lack distinct capsules.
Lingual tonsils
is situated in the posterior wall of the nasopharynx, is covered by pseudostratified ciliated columnar epithelium, and has a thin underlying capsule.
pharyngeal tonsil
▪ Location: Wall of the small intestine, resembling tonsils in structure
▪ Capture & destroy bacteria in the intestine
PEYER’S PATCHES
▪ Location: Tubelike offshoot of the 1st part of the large intestine
▪ Has lymphoid follicles, that capture & destroy bacteria.
appendix
2 types of immnunity
innate immunity and adpative immunity
the ability to resist infection by means of normally present body functions.
INNATE IMMUNITY
acquired gradually by exposure to microorganisms
adaptive immunity
Non-specific and without memory
innate immunity
Specific and with memory
Adaptive immunity
innate immunity is mediated by:
Granulocytes and other leukocytes
adaptive immunity is mediated by
lymphocytes and antigen presenting cells (APCs)
cells involved in innate immunity
Phagocytes, Basophils, Macrophages, Dendritic cells
cell involved in adaptive immunity
b and t cell
response time of innate immunity
immediate
response time of adaptive immunity
delayed
occurrence of innate immunity
natural
occurrence of adaptive immunity
stimulated
processes involved in innate immunity
phagocytosis and antigen preservation
processes involved in adaptive immunity
b-cell activation and t-cell activation
specifity of innate immunity
non-specific
specificity of adaptive immunity
specific
life span of innate immunity
short term
span of adaptive immunity
long term
phatogen recognition of innate immunity
toll-like receptors
phatogen recognition of adaptive immunity
memory cells
Mechanisms protect against a variety of invaders. • Responds immediately to protect the body from all foreign materials.
INNATE IMMUNITY/INNATE BODY DEFENSE
what are the first line of defense?
skin
intact mucous membranes
Forms mechanical barrier to foreign materials
skin
Skin secretions (pH 3-5) make epidermal surface acidic, inhibits bacterial growth; sebum also contains bacteria-killing chemicals.
acid mantle
Provides resistance against acids, alkalis, & bacterial enzymes.
keratin
Form mechanical barrier that prevents entry of pathogens
intact mucous membranes
Traps microorganisms in respiratory & digestive tracts
mucus
Filter & trap microorganisms in nasal passages
nasal hairs
Propel debris-laden mucus away from lower respiratory passages
cilia
Contains concentrated HCl & protein-digesting enzymes that destroy pathogens in stomach
gastric juice
Inhibits growth of bacteria & fungi in female reproductive tract
acid mantle of vagina
Continuously lubricate & cleanse eyes (tears) & oral cavity (saliva); contain lysozyme, an enzyme that destroys microorganisms
Lacrimal secretion (tears); saliva
First Line of Defense
Surface Membrane Barriers
Second Line of Defense
Cellular & Chemical Defenses
what are the second line of defense?
phagocytes
natural killer cells
inflammatory response