A & P II - Chapter 20 - Lymphatic System

What does the lymphatic system consist of?

• Lymph

• Lymphatic Vessels

  • Lymphatic Organs

Major functions of Lymphatic System

• Return fluiods that leak blood vessels back to blood

• Production, maintenance and distribution of lymphocytes

  • Defends body against pathogens

    • Small intestine → Lacteals absorb fat

Lymphatic Vessels are

A One way system and responsible for the transport of lymph

Lymphatic Capillaries

flow towards the heart

Location of lymphatic capillaries

Near blood capillaries; absorbs blood through blood capillaries

Lymphatic capillaries

allow fluids to enter but will not exit out of the capillary

Capillaries

Take up bacteria, cancer cells, proteins and microbes

Lymphatic Collecting Vessels are most similar to 

Veins because they have valves

Lymphatic Collecting vessels

contain large amounts of anastamoses

Lymphatic Collecting Vessels hav

3 tunics

Location of Lymphatic Collecting Vessels

Near superficial veins in skin and arteries of viscera

Lymph flow throughout the body

1. Lymphatic Capillaries

2. Lymphatic Collecting Vessels

3. Lymphatic Trunks

Lymphatic Trunks

Drain large areas of the body

Lymphatic trunks travel

within deep arteries and are named for the region drained

Lymphatic Ducts

recieve lymph from trunks

Thoracic Duct

Drains from most of the body

Right Lymphatic Duct

Drains the Right Arm, Right Head & Thotax

Lymph will enter into venous circulation from

Junction of Subclavian and Internal Jugular Veins

The transport of lymph is a

Low pressure system with no pump

• relation to veins

  • Valves, muscular pump, respiratory pump, smooth muscle

Edema

Fluid build up 

Lymphoid Tissue is composed of

Reticular CT

• Cells & Fibers

The cells and fibers in the reticular CT provide for

Proliferation sites for lymphocytes and macrophages

Macrophage 

On fiber

Lymphocytes are located

between cells

• they offer a vantage point on surveillance as they filter through lymph

Primary Lymphatic Organ

Sites where stem cells divide and become immunocompetent

Immunocompetent

Ability to carry out an adaptive immune response

Examples of Primary Lymph Organs

Red Bone Marrow and Thymus

Secondary Lymphatic Organs

Sites where responses occure

Secondary Lymph organs examples

• Lymph nodes

• Spleen

• Tonsils

• Peyer’s patches

  • Appendix

Red Bone Marrow

• Site of origin for all blood cell types

• Give rise to B cells and Pre-T cells

  • B Cells mature here

Thymus

• T Cells will mature

• Gain surface receptors

  • Has only T cells → does not directly fight against antigens

What hormones does the thymus secrete

Thymosin & Thymopoietin

Spleen

Largest organ in body

• Filter blood and immunological surveillance

The spleen has 2 regions

The white pulp and red pulp

White pulp

B&T cells are located around central arteries

Red pulp

Filtering of blood takes place here; contains venous sinuses → which contain sinusoids

The spleeen is where

Red blood cells are formed during fetal development

Lymph nodes

Approximately 600 that are located near the body’s surface

• 0.4 - 1 inches in diameter ; they are small, oval and located along the lymphatic vessels

Lymph nodes are filled with

B&T cells and macrophages

Main function of lymph nodes

Filter lymph

• this is where immune system is activated and pathogens are destroyed

Afferent Lymphatic Vessel 

EntersE

Efferent lymphatic vessel

Exits

How to travel

Through subscapular sinus to midullary sinusesT

There are fewer 

efferent vessels due to the flow being slow and regulated

Lymphatic nodules

MALT tissue

• lymphoid tissue and mucous membranes

  • They are scattered throughout respiratory, digestive, urinary and reproductive systems

Palantine Tonsils

Oropharynx

Pharyngeal Tonsils

Nasopharynx

Peyer’s Patch

Small & Large Intestine