Lymphatic System

lymphatic vessels

“Pick up” fluid lost from capillaries, filters it (lymph nodes), and returns it to the bloodstream

how much fluid leaks from our capillary beds

3L of fluid due to pressure gradients that favor the movement of fluid into the interstitial space

hydrostatic pressure

exerted by blood on the inside wall of the vessel; forces blood plasma out of the vessel. (start)40 mmHg→ 20 mmHg(end)

osmotic (oncotic) pressure

exerted by plasma proteins (albumin); pulls fluid into the vessel. Stays @ 25mmHg

net loss of fluid

• Beginning of capillary: 40 – 25 = 15mmHg pushing fluid out.

• End of capillary: 25 – 20 = 5 mmHg pulling fluid into capillary.

• Overall: more fluid leaves the capillary than is returned

location of lymphatic cells

Found everywhere except:
CNS, bones, bone marrow, and teeth.
• One-way flow

types of lymph

Lymphatic capillaries*

lymph

Interstitial fluid that enters lymphatic capillaries

lymphatic capillaries

in close contact with blood capillaries but are more permeable. cells will act as mini-valves that are opened by interstitial pressure

lacteals

specialized lymph capillaries in the intestines: absorb digested fat and deliver it to the blood

Lymphatic capillaries can absorb

cell debris, pathogens, cancer cells

lymphatic ducts

lymph returned to the blood stream via the 2 lymphatic ducts. Ducts merge with large neck veins

right lymphatic duct

drains the right arm and right side of the head and thorax

thoracic duct

drains the rest of the body

primary lymphatic structure

involved in formation and maturation of lymphocytes (red bone marrow, thymus)

secondary lymphatic structures

house lymphocytes and macrophages

Red Bone Marrow

located in spongy bone of the skull, ribs, sternum, vertebrae, coxal bone, and heads of humerus and femur. All blood cells produced here

t-lymphocytes

WBC that migrates to thymus to complete maturation. destroy virus infected cells

b-lymphocytes

mature in the red bone marrow.

thymus

secretes hormones thymosin and thymopoietin that helps T lymphocytes gain immunocompetence

immunocompetence

lymphocytes programmed to recognize and respond to a specific antigen

antigen

anything the body perceives as foreign and provokes an immune response such as:

1. pathogens (bacteria, virus)

2. mismatched RBC’s

3. transplanted tissue

4. cancer cells

t-cells

manage the immune response and uses “chemical warefare” to attack/destroy foreign or infected cells

b-cells

produce plasma cells (secrete antibodies). Antibodies immobolize antigens

macrophages

use phagocytosis to destroy antigens and help activate T-cells

lymph nodes

lymphatic organs clustered along lymphatic vessels. can be found near surface of body in inguinal, axillary, and cervical regions

lymph node structure

• afferent vessels = bring lymph into node

• efferent vessels = carry lymph away

• afferent > efferent (increase time for filtering)

lymph node function

filtration = cleans lymph by destroying antigens and debris

spleen

largest lymphatic organ that sits in the LUQ under the diaphragm

Spleen function

macrophages clean blood = old RBC’s, platelets, and cellular debris removed

spleen structure

• highly vascularized

• hilum = indented area where anything that enters/exits spleen does so (blood vessels)

MALT (mucosa-associated lymphatic system)

found in respiratory and digestive tracts to protect against antigens by housing lymphocytes and macrophages

MALT structure

1. peyers patches and appendix (digestive tract)

2. tonsils (pharynx)

3. lymphatic nodules that surround airways (respiratory tract)

types of tonsils

1. palatine tonsils = posterior oral cavity

2. linguinal tonsils = posterior tongue

3. pharyngeal tonsils = posterior nasopharanyx

4. tubal tonsils = surround openings of auditory tubes into the pharanyx

tonsils

lymphocytes and macrophages wait in crypts to destroy pathogens.

advantage of lymphoid tissue

bits of it are found in every organ in the body which gives lymphocytes and macrophages (warrior cells) more places to fight antigens