Ch. 14 Lymphatic System Flashcards
The lymphatic system is also named..
(Reticuloendothelial system, defensive system, immune system)
The lymphatic system is also known as..
A 2nd circulatory system
Lymphatic vessels collect and carry away excess tissue fluid from..
Interstitial spaces, eventually returning it to the blood
Lymph nodes, which are situated along lymphatic vessels, contain..
Lymphocytes, which help defend body against infection
The lymphatic pathway is..
Arterioles (blood) —> Capillaries (Vein-Blood) —> Tissue (Interstitial fluid) —> Lymphatic capillaries (Lymph) —> Lymph node —> Lymphatic ducts —> Either RT Lymphatic duct or Thoracic duct which drain into the RT or LT Subclavian vein
Lymphatic capillaries:
- Tiny, closed-ended tubular vessels that extend into interstitial spaces, paralleling the blood capillaries
- Found all over body, except in central nervous system
- Receive tissue (interstitial) fluid through their thin walls and slits between cells
- Once inside a lymphatic capillary, tissue fluid is called lymph
Lymphatic capillaries: Tiny, closed-ended tubular vessels that extend into..
Interstitial spaces, paralleling the blood capillaries
Lymphatic capillaries: Found all over body, except in..
Central nervous system
Lymphatic capillaries: Receive tissue (interstitial) fluid through their..
Thin walls and slits between cells
Lymphatic capillaries: Once inside a lymphatic capillary, tissue fluid is called..
Lymph
Lymphatic vessels:
- Walls of lymphatic vessels are thinner than those of veins, but they are constructed with the same 3 layers
- Have flaplike valves on the inside, like veins
- Prevent backflow - Larger lymphatic vessels pass through organs called lymph nodes, and then merge to form larger lymphatic trunks
Lymphatic vessels: Walls of lymphatic vessels are thinner than those of veins, but they are constructed with..
The same 3 layers
- (1) Tunica interna
- Inner layer
- Made of simple squamous epithelium
- Also called endothelium
- Direct contact with blood
- Prevent blood clotting
- (2) Tunica media
- Middle layer
- Thickest layer
- Consist 2 layers: (1) Elastic connective tissue, (2) Smooth muscle
- [Tube-like structures are made up of smooth muscle]
- Functions: (1) Elasticity/contractibility, (2) Help maintaining blood pressure
- (3) Tunica externa (Tunica adventitia)
- Formed by fibrous connective tissue
- Very strong
- Prevent rupturing of the blood vessel because of pressure beared from the left ventricle
Lymphatic vessels: Have flaplike valves on the inside, like veins to
Prevent backflow
Lymphatic vessels: Larger lymphatic vessels pass through organs called..
Lymph nodes, and then merge to form larger lymphatic trunks
Lymphatic trunks:
- Drain lymph from the lymphatic vessels
- Named for the regions they drain
Trunks empty into 1 of 2 collecting ducts:
Thoracic or right lymphatic duct
Right lymphatic duct: Drains..
Right side of head and neck, right arm, and right thorax, and empties into right subclavian vein
Thoracic duct:
Larger collecting duct, drains rest (majority) of the body, and empties into left subclavian vein
Lymph:
- Tissue fluid that has entered a lymphatic capillary
- Lymph formation depends on tissue fluid formation
Tissue fluid formation:
- Tissue fluid is made up of water and dissolved substances that leave blood capillaries by filtration and diffusion
- [Diffusion: Movement from high to low concentration] - [Filtration: Water and dissolved material forced through a membrane from high to low pressure]
Fluid that does not return to the capillaries becomes..
Tissue fluid
Lymph also transports foreign particles, including bacteria and viruses, to the lymph nodes for..
Recognition and destruction
Factors that help in the movement of lymph:
- Hydrostatic pressure of tissue fluid
- Muscular activity moves lymph through lymphatic vessels:
- Skeletal muscle contraction
- Breathing movements
- Contraction of smooth muscle in the walls of the vessels
- Valves prevent backflow - Edema: Accumulation of lymph in the interstitial spaces, due to interference with flow in lymph
- [Edema: When fluid goes between tissue]
- EX: During surgery, such as removing cancerous breast, lymphatic vessels or tissues may be removed or disturbed; obstruction results in edema
Lymphatic tissue contains..
Lymphocytes, macrophages, and other cells
Lymphatic organs:
- Lymph nodes
- Thymus
- Spleen
- Tonsils
- Appendix
Lymph nodes: Location
- In groups or chains along lymphatic vessels
- Not found in the central nervous system
- Major areas of concentration: Cervical, thoracic, axillary, supratrochlear, abdomial, pelvic, and inguinal regions
Lymph nodes: Structure
- Lymph nodes are bean-shaped,(kidney-shaped— Reniform)
- Blood vessels, nerves, and efferent lymphatic vessens enter or exit at the indent hilum or hilus
- Afferent lymphatic vessels enter on the convex surface
- Lymph nodes are covered with a connective tissue capsule, that extends inside the node and divides it into lymphatic nodules and spaces called sinuses
- Lymph nodes contain both lymphocytes and macrophages; they filter the lymph as it flows through them, removing many pathogens
- Filtered lymph leaves lymph node through efferent lymphatic vessels
Lymph nodes: Function
- Filter lymph and remove bacteria and cellular debris before lymph is returned to the blood
- Immune surveillance: Monitor body fluids; performed by lymphocytes and macrophages
- Lymph nodes are also centers of lymphocyte production
- Lymphocytes attack viruses, bacteria and parasitic cells that enter a lymph node
- Macrophages engulf and destroy foreign particles, debris, and damaged cells
Thymus: Location
- Behind the sternum
- Anterior to aorta
Thymus: Structure
- Soft, bi-lobed organ
- Shrinks in size during the lifetime, large in children, small in adults, replaced by adipose and connective tissue in the elderly
- Surrounded by a connective tissue capsule that extends inward and divides it into lobules
- Lobules contain lymphocytes, some of which mature into T cells or T lymphocytes, that leave the thymus to provide immunity
Thymus: Function
The thymus secretes hormones called thymosins, which influence maturation or T lymphocytes
Spleen: Location
Lies in the upper left abdominal cavity (left hypochondriac region/LUQ)
Spleen: Relational anatomy
- The spleen is bordered by surrounding organs and structures:
- Anterior by:
- Medially by:
- Posteriorly by:
- Anterior by: Stomach
- Medially by: Left kidney, splenic flexure of colon, pancreatic tail
- Posteriorly by: Diaphragm, pleura left lung, ribs
Spleen: Structure
- Largest lymphatic organ in the body
- Similar to a large lymph node, except it contains blood instead of lymph
- Composed of white pulp, which contains many lymphocytes, and red pulp, which contains red blood cells, macrophages, and lymphocytes
Spleen: Function
Filters the blood and removes damaged blood cells and bacteria
Pathogens:
- Disease-causing agents
- Presence and multiplication can produce an infection
- Can be bacteria, viruses, fungi, or protozoans
Two basic mechanisms of defenses:
- Innate (Nonspecific) defenses:
- Guard against many types of pathogens; respond quickly
- Include species resistance, mechanical barriers, chemical barriers, natural killer cells, inflammation, phagocytosis, and fever - Adaptive (Specific) defenses or immunity:
- Respond against only a specific type of pathogen; respond more slowly
- Accomplished by specialized lymphocytes, which secrete cytokines or antibodies
Innate (Nonspecific) Defenses: Mechanical barriers
- The body’s first line of defense (the rest of the innate defenses are part of the 2nd line of defense
- Prevent the entry of certain pathogens by providing a physical separation of pathogens and internal tissues
- Includes hair, mucus, and sweat
Innate (Nonspecific) Defenses: Chemical barriers
- Chemicals that kill many pathogens
- Acidic environment
- Enzymes— Destroy many pathogens
- Interferons— Block viral replication and slow tumor growth
- Complement— Attracts phagocytes and enhances phagocytosis and antibody action
Adaptive (Specific) Defenses or Immunity:
- Third line of defense
- Response by the body against specific pathogens, their toxins or metabolic products
Hilum/hilus:
Door in which vessels move in and out
