lymphatic system and body defenses chapter 12. the lymphatic system two semi-independent parts –...
TRANSCRIPT
Lymphatic System and Body DefensesLymphatic System and Body Defenses
Chapter 12Chapter 12
The Lymphatic SystemThe Lymphatic System
• Two semi-independent parts– Lymphatic vessels
– Lymphoid tissues and organs
• Function of lymphatic system– Transport fluids back to the blood
– Essential role in body defense and disease resistance
Lymphatic VesselsLymphatic Vessels
• Function– Pick up excess tissue fluid – Lymph – and return it
to the blood stream
• Also known as lymphatics• One way system flows only to the heart• Characteristics
– Thin-walled– Valved– pumpless
Lymph capillariesLymph capillaries
• Web between tissue cells and blood capillaries
• Remarkably permeable
• Held by fine collagen fibres
• Act as one way doors– Flap like mini valves close as high pressure builds
up inside
– Keeps lymph from leaking back
Lymphatic collecting vesselsLymphatic collecting vessels
• Collects lymph from lymph capillaries
• Carries lymph to and away from lymph node
• Returns fluid to the heart through two ducts– Right lymphatic duct
• Drains lymph from right arm and right side of head and thorax
– Thoracic duct• Receives lymph from rest of the body
Lymphatic VesselsLymphatic Vessels
Lymph NodesLymph Nodes• Function
– Remove foreign material from lymph
• Cluster along vessels in three main areas– Inguinal– Axillary– Cervical
• Contain 2 types of cells– Macrophages
• Engulf and destroy bacteria, viruses and foreign substances
– Lymphocytes (white blood cells)• Respond to foreign substances
Lymph Nodes (continued)Lymph Nodes (continued)
• Structure– Kidney shaped, less than 1” long– “buried” in connective tissue– Cortex
• Outer part• Contains follicles (collections of lymphocytes) and T-
cells
– Medulla• Inner part• Contains phagocytic macrophages
Flow of Lymph through NodesFlow of Lymph through Nodes
• Lymph enters through afferent lymph vessels
• Flows through sinuses
• Exits at indented region - hilus – through efferent lymphatic vessels
• Slow process– Allows time for lymphocytes and macrophages to
perform
Other Lymphoid OrgansOther Lymphoid Organs
• Spleen
• Thymus
• Tonsils
• Peyer’s patch
• Common features– Predominance of
reticular connective tissues and lymphocytes
Other Lymphoid OrgansOther Lymphoid Organs• Spleen
– Filters blood of bacteria, viruses
– Located on left side of abdominal cavity
– Destroys worn out red blood cells
– Acts as blood reservoire
– Produces lymphocytes
• Thymus– Function peaks at youth
– Found low in throat over heart
– Produces hormones that program lymphocytes
Other Lymphoid OrgansOther Lymphoid Organs
• Tonsils– Small masses of lymphatic tissue around pharynx
– Trap and removes bacteria or pathogens entering throat
– So efficient can become congested• tonsillitis
• Peyer’s patches– Like tonsils but in small intestine
– Captures and destroys bacteria
Mucosa-associated Lymphatic Tissue (MALT)
Mucosa-associated Lymphatic Tissue (MALT)
• Composed of– Peyer’s patches
– Tonsils
– Other small collections of lymphatic tissue
• Protects respiratory and digestive tracts
Body DefensesBody Defenses
Nonspecific Body DefensesNonspecific Body Defenses
Specific Body Defenses: The Immune System
Specific Body Defenses: The Immune System