Lymphatic System Flashcards
(39 cards)
What is lymph?
Lympth is interstitial fluid that has entered the lymphatic vessels. Lymph is a clear, pale-yellow fluid
Lympathic system consists of
lymphatic vessels, lymph, lymph nodes, thymus, spleen, GALT & MALT, red bone marrow
Lymphatic tissue is made of
Lymphatic tissue is made of a specialized form of reticular connective tissue. Lymphatic tissue contains large numbers of lymphocytes
Functions of Lymphatic System
- Drains excess interstitial fluid
- Transports dietary lipids
- Carries out immune responses
Lymphatic Vessels & Lymph Circulation
1, Begins as lymphatic capillaries
(tiny and closed at one end and located in spaces between cells)
2. Lymphatic capillaries unite to form larger lymphatic vessels (resemble veins but have thinner walls and more valves)
3. Lymph flows through lymph nodes
In skin:
Lymphatic vessels located in subcutaneous tissue, following the same route as veins
In viscera:
Lymphatic vessels follow same route as arteries, forming plexuses (networks) around viscera
Tissues that lack lymphatic vessels:
Avascular tissues, eg. cornea, lens, cartilage, CNS - brain and spinal cord
Structure of lymphatic capillaries
Larger in diameter than blood vessels
Have a one way structure - only permits in flow of interstitial fluid
Flow of Lymph
Blood capillaries (blood) > Interstitial spaces (interstitial fluid) > Lymphatic capillaries (lymph) > Lymphatic vessels (lymph) > Lymphatic ducts (lymph) > Junction of the internal jugular and subclavian veins (blood)
Lymphatic Ducts
Lymph passes from trunks into two main channels
- Thoracic duct (aka left lymphatic duct)
- Right lymphatic duct
Thoracic duct
The thoracic duct is the main duct for the return of lymph to blood
- 38-45cm long
- Main duct for the return of lymph to blood
- Drains lymph from most of the trunks: L & R Lumbar, Intestinal, L Jugular, L Subclavian, L Bronchomediastinal
- Then drains lymph into venous blood stream at junction of L internal jugular & L subclavian vein
Spleen
white pulp, red pulp
Lymph nodes
Act as a filter, cleaning the lymph
Same two pumps involved in venous return of blood to heart maintain flow of lymph
- Skeletal muscle pump – “milking action” of skeletal muscles compresses lymphatic vessels
- Respiratory pump – Pressure changes occuring during inhalation and exhalation
Primary Lymphatic Organs
Sites where stem cells divide and become immunocompetent (can mount an immune response)
- Red Bone Marrow – pluripotent stem cells give rise to:
- Immunocompetant B cells
- Pre-T cells - Thymus
- Pre-T cells migrate to thymus to finish their maturation > immunocompetent T cells
Secondary Lymphatic Organs
Sites where most immune responses occur
- Lymph nodes – organ (surrounded by a capsule)
- Spleen - organ
- Lymphatic nodules (follicles) – non organ (lacks a capsule)
What does the lymphatic system pick up, that is not reabsorbed?
Perhaps plasma proteins as molecules are too large
What do macrophages do in the thymus?
Thymic macrophages help clear debris of dead and dying cells
What is innate (non-specific) immunity?
External and internal physical and chemical defences which act in a non-specific way. Innate immunity is present from birth. Prevent access of microbes, or help eliminate microbes in the body.
What is the body’s first line of defence? Innate (non-specific) Immunity
Part of Innate (non-specific) Immunity, the body’s first line of defence is the skin and mucous membrane. Both provide physical and chemical barriers against pathogens entering to cause disease.
How does the skin (epidermis being the exterior) protect the body against pathogens, in Innate (non-specific) Immunity?
Innate (non-specific) Immunity & Skin (first line of defence)
- Keratin: many layers of closely packed keratinised cells
- Acid Mantle: sebaceous glands producing oily sebum
How does the epithelial layer of mucous membranes protect the body against pathogens, in Innate (non-specific) Immunity?
Innate (non-specific) Immunity & Mucous membranes (first line of defence). Mucous membranes line body cavities and secrete a mucous to trap microbes. Examples of how mucous membranes form the first line of defence: Mucous Gastric juice Nasal hairs Cilia Lacrimal secretions Saliva Urine Vaginal secretions Vomiting & Defecation
How does the second line of defence protect the body?
The second line of defence is used whenever first line has been penetrated. The second line of defence involves internal defenses such as:
- Antimicrobial Substances
- Natural Killer (NK) cells
- Phagocytes
- Inflammatory Response
- Fever