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A+P 2 > chp 20 > Flashcards

chp 20 Flashcards

1
Q

lymphatic system function

A
  • Returns fluids leaked from blood vessels back to blood
  • Provide structural basis of immune system
  • House phagocytic cells and lymphocytes
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2
Q

lymphatic system has three parts

A
  1. lymphatic vessels (lymphatics)
  2. Lymph: fluid in vessels
  3. Lymph nodes: clean the lymph
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3
Q

lymphoid organs and tissues

A

spleen, thymus, tonsils, lymph nodes, other lymphoid tissues

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4
Q 
Lymphatic organs and tissues 
Returns \_\_\_\_ per day
lymph
fluid that has gone into the
-Includes
A
  • Returns interstitial fluid and leaked plasma proteins to the blood
  • Network of vessels
  • Returns ~ 3L interstitial fluid per day
  • Lymph
  • –Interstitial fluid that has gone into the lymphatics
  • Include lymphatic capillaries and larger lymphatic vessels
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5
Q

Distribution and Structure of Lymphatic Vessels

____system

A

One-way system only toward heart

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6
Q 
Lymphatic capillaries
Weave between
found where
Similar to
Can act as route for
A
  • Blind-ended vessels
  • Weave between tissue cells and blood capillaries
  • Where?
  • -Almost everywhere NOT: bones, teeth, and bone marrow
  • -Even some in the central nervous system!
  • —-Once thought to be absent from CNS, but now found to be present but limited to locations in meninges where they help to drain interstitial fluid and CSF.
  • Similar to blood capillaries, but more permeable
  • Larger molecules and particles can enter
  • -Example: proteins, cell debris, pathogens, and cancer cells
  • Can act as route for pathogens or cancer cells to travel throughout body
  • –This is one way cancers spread…
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7
Q

what makes the capillaries so permeable?

A

one-way minivalves

  • Anchored by collagen filaments to matrix
  • Increases in ECF volume opens minivalves
  • Decreases in ECF cause minivalves to close
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8
Q

Lacteals

A
  • specialized lymph capillaries in intestinal mucosa
  • –What’s mucosa again?
  • Absorb digested fat and deliver fatty lymph (chyle) to the blood
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9
Q

Collecting lymphatic vessels
Have structures and tunics similar to
Collecting vessels travel with

A
  • Drain lymph capillaries
  • Collecting vessels, trunks, and ducts
  • Have structures and tunics similar to veins, except:
  • –Have thinner walls, with more internal valves
  • –Anastomose more frequently
  • Collecting vessels travel with superficial veins, but deep vessels travel with arteries
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10
Q

Lymphatic trunks

A
  • Formed by joining together largest collecting vessels
  • Drain large areas of body
  • –Named for regions of body they drain:
  • Paired lumbar
  • Paired bronchomediastinal
  • Paired subclavian
  • Paired jugular trunks
  • Single intestinal trunk
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11
Q

what collects lymph from the trunks

A
  • Right lymphatic duct
  • –Drains right upper arm and right side of head and thorax
  • Thoracic duct
  • –Drains rest of body
  • Cisterna chyli
  • –Beginning of thoracic duct
  • –Only in about 50% of people

-Both empty the junction of internal jugular and subclavian veins on its own side of body

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12
Q

Lymph Transport

physical activity

A
  • Low-pressure system like venous system
  • Lymph is moved the way venous blood is moved:
  • –Milking action of skeletal muscle
  • –Pressure changes in thorax during breathing
  • –Valves to prevent backflow
  • –Pulsations of nearby arteries
  • –Contractions of smooth muscle in walls of lymphatics
  • Physical activity increases flow of lymph
  • Immobilization
  • –Keeps inflammatory material in area for faster healing
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13
Q

Lymphedema

A

-severe localized edema

  • Caused by anything that prevents normal return of lymph to blood
  • –Examples: tumors blocking lymphatics or removal of lymphatics during cancer surgery
  • –Lymphedema may improve if some lymphatic pathways remain and enlarge
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14
Q

Lymphoid cells consist of

A

of (1) immune system cells found in lymphoid tissue and (2) supporting cells that form lymphoid tissue structures

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15
Q

Immune system cells
Lymphocytes:

-T cells and B cells both protect against

A

Lymphocytes: cells of the adaptive immune system; mature into one of two main types

  • T cells (T lymphocytes)
  • -manage immune response, and some also attack and destroy infected cells
  • B cells (B lymphocytes)
  • -produce plasma cells, which secrete antibodies
  • -Antibodies mark antigens for destruction by phagocytosis or other means

-T cells and B cells both protect against
Antigen: anything the body perceives as foreign
Examples: bacteria, toxins, viruses, mismatched RBCs, cancer cells

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16
Q

Other lymphoid immune cells

A
  • Macrophages
  • -phagocytize foreign substances
  • -help activate T cells
  • Dendritic cells
  • -capture antigens and deliver them to lymph nodes
  • -help activate T cells
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17
Q

Supporting lymphoid cell

A

Reticular cells

  • produce reticular fibers to form the stroma
  • Stroma
  • -scaffolding for immune cells to hole on to
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18
Q

Lymphoid Tissue
Structural composition
offers ______points for ________ as they filter lymph

Macrophages live on
Lymphocytes live in

A
  • House and provide proliferation sites for lymphocytes
  • -Offers surveillance vantage points for lymphocytes and macrophages as they filter lymph

reticular connective tissue

  • -Loose connective tissue
  • -Macrophages live on reticular fibers
  • -Lymphocytes live in the spaces between the fibers when they are not out hunting
19
Q

Two main types of lymphoid tissues

A

Diffuse lymphoid tissue

  • -loose arrangement of lymphoid cells and some reticular fibers
  • -Found in virtually every body organ
  • -Larger collections in lamina propria of mucous membranes

Lymphoid follicles (nodules)

  • Solid
  • spherical bodies with packed lymphoid cells and reticular fibers
  • Germinal centers
  • -proliferating B cells
  • May form part of lymph nodes
  • Found Peyer’s patches and in appendix
20
Q

Lymphoid organs are grouped into two functional categories

-Both T and B cells originate in

A
  • Primary lymphoid organs
  • Where T and B cells mature—
  • -B in the red bone marrow
  • -T in the thymus
  • -Both T and B cells originate in bone marrow
  • Secondary lymphoid organs
  • -Areas where mature lymphocytes first encounter their antigen and become activated
  • -I.e: Nodes, spleen, MALT (mucosa-associated lymphoid tissue) and diffuse lymphoid tissues
21
Q

Lymph nodes
-secondary lymphoid organs of body

-Where ______ come together and form

A

-Main secondary lymphoid organs of body

  • Hundreds found throughout body
  • -Embedded deep in connective tissue in clusters along lymphatic vessels (most)
  • -Some are nearer to body surface
  • –inguinal, axillary, and cervical regions
  • –Where collecting vessels come together and form trunks
22
Q

lymph nodes two major functions

A
  1. Filter the lymph
    - -Macrophages remove and destroy microorganisms and debris that enter lymph
    - -Prevent unwanted substances from being delivered to blood
  2. Immune system activation
    - -Place for lymphocyte activation
    - -Place for lymphocytes to attack antigens
23
Q

Structure of a Lymph Node

A
  • Vary in shape and size
  • Most are bean shaped
  • Small
  • -less than 2.5 cm (~1 inch)
  • External fibrous capsule
  • Trabeculae
  • -Capsule fibers that extend inward
  • -Divide node into compartments
  • Two regions of node:
    1. Cortex
    2. Medulla
24
Q

Cortex

A
  • Superficial (outer part)
  • Follicles with germinal centers
  • -Dividing B cells
  • Deeper in the cortex
  • -T cells in transit
  • -T cells circulate continuously among blood, lymph nodes, and lymph
  • Lots of dendritic cells
  • -Play a role in activating T cells and B cells
  • -Reminder-T cells and B cells are types of lymphocytes!
25
Q

Medulla

A
  • Medullary cords
  • -Extend inward from cortex
  • -Contain B cells, T cells, and plasma cells
  • Lymph sinuses
  • -Found throughout node
  • -Large lymphatic capillaries
  • -Mesh of reticular fibers
  • –Macrophages attach to the fibers
  • –Check for and phagocytize foreign matter
26
Q

Lymph enters via

A
  • afferent lymphatic vessels
  • Travels through large subcapsular sinus and then into smaller sinuses found throughout cortex and medulla
  • Lymph then enters medullary sinuses
  • Finally exits at hilum via efferent lymphatic vessels
  • –Presence of fewer efferent vessels causes flow to somewhat stagnate
  • –Allows lymphocytes and macrophages time to function
  • –Lymph travels through several nodes
27
Q

Buboes

A
  • Inflamed, swollen, tender lymph nodes
  • When nodes are overwhelmed by what they are trying to destroy
  • Often called swollen “glands”
  • Buboes are sometimes pus-filled
  • Bubonic plague was named after the buboes it causes!
28
Q

Lymph nodes can become secondary

A

secondary cancer sites if metastasizing cancer cells become trapped in node
-Cancer-infiltrated lymph nodes are swollen but usually not painful, a fact that helps distinguish cancerous nodes from those infected by microorganisms

29
Q

Spleen

structure and function

A
  • Spleen blood-rich
  • About size of fist
  • Located in left side of abdominal cavity, just below stomach
  • Largest lymphoid organ
  • Served by splenic artery and vein, which enter and exit at the hilum
  • Encased by fibrous capsule and has trabeculae
  • Functions
  • Site of lymphocyte proliferation and immune surveillance and response
  • Cleanses blood of aged blood cells and platelets; macrophages remove debris
  • Stores breakdown products of RBCs (e.g., iron) for later reuse
  • Stores blood platelets and monocytes for release into blood when needed
  • May be site of fetal erythrocyte production
30
Q

spleen Histologically, consists of two components

A
  • White pulp
  • -Immune function
  • -Mostly lymphocytes on reticular fibers
  • -Clusters are found around central arteries
  • —islands of white in a sea of red pulp
  • Red pulp
  • -Where old blood cells and bloodborne pathogens are destroyed
  • Rich in RBCs and macrophages that engulf them
  • Splenic cords
  • –reticular tissue
  • -separate blood-filled splenic sinusoids (venous sinuses)
31
Q

The spleen has a thin capsule, so direct blow or severe infection may cause it to

A

rupture, spilling blood into peritoneal cavity

This can lead to shock and death!

32
Q

Splenectomy

A
  • Surgical removal of ruptured spleen
  • Used to be the standard to prevent hemorrhage and shock
  • BUT we now know the spleen can often repair itself
  • -Frequency of emergency splenectomies has decreased dramatically
  • If spleen removed
  • –liver and bone marrow take over most of its functions
  • -In children younger than 12, spleen will regenerate if a small part is left!
33
Q

Mucosa-associated lymphoid tissue (MALT)

A

Lymphoid tissues in mucous membranes throughout body

  • Protects from pathogens trying to enter body
  • Locations:
  • –respiratory tract
  • -genitourinary organs
  • -digestive tract
  • -largest collections of MALT found in:
  • —Tonsils
  • —Peyer’s patches
  • —Appendix
34
Q

Tonsils

A

Simplest lymphoid organs
Ring of lymphatic tissue around pharynx
Look like swellings of mucosa
Named according to location

35
Q

palatine tonsils

A

Posterior end of oral cavity
Largest of tonsils
Most often infected

36
Q

Lingual tonsil

A

base of tongue

37
Q

Pharyngeal tonsil

A

AKA adenoids

in posterior wall of nasopharynx

38
Q

Tubal tonsils

A

surround openings of auditory tubes into pharynx

39
Q

Tonsils (Function and Structure)

A
  • Function
  • —Gather and remove pathogens in food or air
  • Contain follicles with germinal centers and scattered lymphocytes
  • Are not fully encapsulated
  • Overlying epithelium invaginates, forming tonsillar crypts
  • –Bacteria or matter get into the crypts and get trapped
  • -Immune cells to become activated and build memory cells against these potential pathogens
40
Q

Peyer’s patches

A
  • Clusters of lymphoid follicles in wall of small intestine
  • AKA aggregated lymphoid nodules
  • Structurally similar to tonsils
  • Location aids in functions
  • -Destroy bacteria to prevent them from escaping the intestines
  • -Generate “memory” lymphocytes
41
Q

Appendix

A
  • Offshoot of first part of large intestine
  • Has a large number of lymphoid follicles
  • Location aids in functions (like Peyer’s patches)
  • -Destroy bacteria, preventing them from breaching intestinal wall
  • -Generate “memory” lymphocytes
42
Q

Thymus

A

bilobed lymphoid organ
Inferior neck into mediastinum and partially overlies heart

Function

  • Where T cells mature
  • Most active and largest in size during childhood
  • Stops growing during adolescence, then gradually atrophies
  • Still produces immunocompetent cells, but is slow
43
Q

Thymus differs from other lymphoid organs in important ways

-stroma has

A
  • No B cells so no follicles
  • Does not fight antigens
  • Functions strictly in T lymphocyte maturation
  • -blood thymus barrier
  • —Keeps immature T lymphocytes away from pathogens so they don’t get activated before they are ready!
  • Stroma
  • –epithelial cells instead of reticular fibers
  • –Where T lymphocytes become immunocompetent

A+P 2 (13 decks)

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