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43 Cards in this Set
- Front
- Back
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Lymphatic System
The circulatory system |
plays a key role in bringing substances to cells & then removing the waste products that accumulate as the result of metabolism
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the capillary beds
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This exchange occurs in the capillary beds
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the capillary wall
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Most of the substances of blood plasma filter freely through the capillary wall however some substance cannot return to the blood vessel
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Functions of Lymphatic System
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Maintain fluid balance in tissues
Lymphatic vessels drain excess interstitial fluid from the tissues spaces & return it to the blood Absorb fats from the digestive tract Carrying out immune responses Body's defense against harmful substances & invading microorganisms |
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Maintaining Fluid Balance
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30L of fluid passes between the blood capillaries & the interstitial fluid each day
Only 27L is returned to the body via the capillaries If the 3L remaining in the interstitial fluid is not returned to the blood stream then gross oedema occurs This would lead to tissue damage & death The lymphatic capillaries take up this excess fluid & returns it to the blood stream The lymphatic system plays an important role in maintaining fluid balance between blood & interstitial fluid |
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Lymphatic System
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Consists of :
Lymph Lymph vessels Lymph nodes |
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Including specialized organs
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Spleen
Thymus gland Tonsils Appendix Peyer's patches |
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Lymph
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The fluid taken up by the lymphatic system is called lymph (clear spring water)
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Lymph is made up of solutes from 2 sources
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Plasma: ions, nutrients, gases & some proteins
Cells: hormones, enzymes & waste products |
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Lymphatic Vessels
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Assist in maintaining fluid balance
Drains excess fluid from the interstitium Carries the fluid & returns it to the blood stream Vessels consist of capillaries & large lymphatic vessels Lymph nodes found dispersed throughout the lymph vessels |
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Lymphatic Vessels
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Range from small to large
Resemble small veins |
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Consists of three layers:
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Endothelium lines the lumen with an elastic membrane
Inner layer of smooth muscle & elastic fibres Thin outer layer fibrous connective tissue |
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Lymphatic Capillaries
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Lymphatic capillaries are vessels that have a free end (not attached)
In almost every tissue in the body Not found in neural tissue, bone marrow, cartilage, epidermis & cornea |
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Lymphatic Capillaries
Are classified as: |
Superficial draining the dermis & hypodermis
Deep draining muscles, joints, viscera & other deep structures |
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Lymphatic Capillaries
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Lack a basement membrane
Simple squamous epithelial cells attach to each other loosely & overlap Are extremely permeable Most things in the interstitial fluid will pass into lymph capillaries Contains one way valves so once things enter the lymphatic system it cannot pass back into the interstitial fluid |
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Drainage of fluid
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Lymph moves forward through lymphatic vessels toward the heart
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Drainage of fluid
Movement is influenced by pressure gradients caused by |
Skeletal muscle contraction
Smooth muscle contraction in the vessel walls Ventilation & pressure changes in the thorax |
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Drainage of fluid
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Moves from an area of high pressure in the tissues to an area of lower pressure in the systemic veins
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Fat Absorption
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Via Lymphatic vessels from digestive system
Some fats cannot be absorbed into the blood stream capillaries as they are too large Fats are coated with a protein then absorbed into cells By simple diffusion into lymphatic lacteals via the wall of the small intestine Also transports lipid soluble vitamins A, D, E & K |
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Lymph Nodes
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At varying intervals along the lymphatic vessels, lymph flows through a chain of structures called lymph nodes
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Lymph Nodes
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Round, oval or bean shaped 1-25mm long
Approx 450 in the body The filtering system within the pathways of lymphatic vessels Bunched together in groups Lymph passes from one lymph node to the next |
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Lymph Nodes
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Filter lymph & removes bacteria & foreign particles
Lymphocytes gather & proliferate in lymph nodes & perform their functions within the lymph node Classified as superficial (hypodermis) & deep (in all other tissues where lymph vessels are found) Both are contained within adipose tissue near blood vessels |
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Node Groups
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Lymph nodes are bunched together in groups which drain certain areas of the body
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Node Groups
Cervical & head: |
drain head & neck
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Node Groups
Axillary nodes: |
drain upper limbs & superficial thorax
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Node Groups
Thorax nodes: |
drain thoracic wall & organs
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Node Groups
Abdomenopelvic nodes: |
drain abdomen & pelvis
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Node Groups
Inguinal & popliteal nodes: |
drain lower limbs & superficial pelvis
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Flow of Lymph
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The lymph then passes from the nodes into lymph trunks that divide into two main channels
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Flow of Lymph
Right Lymphatic duct |
drains lymph from the right arm, right side of head & thorax
drains into right subclavian vein |
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Flow of Lymph
Thoracic duct (left lymphatic) |
drains lymph from remainder of the body
drains into left subclavian vein |
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Flow of Lymph
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These ducts return the lymph fluid to the blood
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Specialised Lymphatic Organs
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Spleen
Thymus gland Tonsils Appendix Peyer’s patches |
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Specialised Lymphatic Organs
Encapsulated within these organs is a lymphatic tissue made up of: |
Lymphocytes (WBC)
Macrophages Dendritic cells Reticular cells |
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Spleen
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Largest single pulp of lymphatic tissue
Size of a clenched fist 180g Located in the left upper abdomen Acts as a reservoir for blood Blood can be returned to circulation when needed During exercise the spleen decreases its blood volume by 40-50% Making a larger volume of blood available for O2 delivery within the blood vessels As blood flows through the pulp foreign substances are filtered & phagocytosed |
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Thymus Gland
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Bi-lobed organ located in mediastinum
Between the sternum & aorta Composed of lymphocytes (T cells, scattered dendritic cells, macrophages) T cells mature in thymus with the assistance of dendritic cells & hormones produced by the thymus They then circulate to the spleen, tonsils, lymph nodes & other lymphatic tissues T cells are critical to immune system functioning |
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Red Bone Marrow
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Found in proximal epiphysis of long bones, vertebrae, sternum, ribs, skull, scapulae, pelvis in adults
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Red Bone Marrow
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Produces lymphoid & myeloid stem cells
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Myeloid stem cells
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reproduce & differentiate into cells that give rise to blood cells
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Lymphoid stem cells
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give rise to lymphocytes
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Tonsils
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Protect against bacteria & foreign substances that are inhaled or ingested
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The five tonsils form a ring at the junction of the oral cavity and the oropharynx
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Pharyngeal (adenoid) tonsil (1) is in the posterior wall of the nasopharynx
Palatine tonsils (2) are either side at the back of the oral cavity Lingual tonsils (2) are at the base of the tongue. |
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Peyer’s Patches
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Similar to tonsils but the lymphatic nodules located in the ileum of the small intestine & appendix
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