Human Anatomy and Physiology II Unit IV Circulation and Body Defense Part 4 The Lymphatic System

Body Defense Us Them Self Your normal cells and tissues Nonself Pathogens, abnormal cells (cancer cells)

Body Defense Defense against non-self requires the combined actions of two body systems: Immune system Lymphatic system

Body Defense Lymphatic system Immune System Network of lymphoid vessels and organs Houses the immune system Immune System The body’s cellular defense system Key players are the white blood cells

Immunity Resistance Susceptibility 2 types of immunity Innate Adaptive

Immunity Innate Nonspecific Birth Early warning system 1st & 2nd lines of defense Adaptive Specific Adapts Detects & destroys Lymphocytes

Lymphatic System Topics Components of the lymphatic system Functions of the lymphatic system Organization of lymphatic vessels Formation and flow of lymph Lymphatic organs

Lymphatic System Components Clear fluid Interstitium  lymphatic vessels Returned to blood by way of lymph ducts Resembles blood plasma Contains WBCs (especially lymphocytes) but few red blood cells and no platelets

Lymphatic System Components Lymphatic vessels Transport lymph Thin walled, many-valved structures Lined by endothelial cells, with a thin layer of smooth muscle and adventitia Skin vs. visceral vessels Drain into subclavian veins

Lymphatic System Components Lymphatic tissue Specialized form of reticular connective tissue containing large numbers of lymphocytes Filtering Makes up the spleen, thymus, tonsils, lymph nodes, and mucosa associated lymphatic tissue

Lymphatic System Components Lymphatic organs Discrete collections of lymphatic tissue; often encapsulated Includes the thymus, spleen, tonsils, and lymph nodes

Lymphatic System Components Bone Marrow RBM Works with thymus Site of lymphocyte production Hematopoietic progenitor cells

Figure 22.1

Lymphatic System Topics Components of the lymphatic system Functions of the lymphatic system Organization of lymphatic vessels Formation and flow of lymph Lymphatic organs

Functions of the Lymphatic System Drain interstitial fluid Return leaked plasma proteins to blood Transport dietary fats and lipid-soluble vitamins Protect against pathogen invasion

Lymphatic System Topics Components of the lymphatic system Functions of the lymphatic system Organization of lymphatic vessels Formation and flow of lymph Lymphatic organs

Organization of Lymphatic Vessels Organized from smallest to largest: Lymphatic capillaries Lymphatic vessels Afferent and efferent Lymph nodes Lymph trunks Lymph ducts

Lymphatic Vessels Locations Structure Functions Alongside small blood veins Structure Similar to small blood veins Functions Receive lymph from lymphatic capillaries Convey lymph into and out of lymph nodes Drain lymph into lymph trunks

Lymphatic Capillaries Locations Everywhere you find blood capillaries Structure Blind-ended Greater permeability Slightly larger diameter than blood capillaries Have one-way valves + overlapping endothelial cells Functions Collect interstitial fluid; form lymph

Figure 22.2

Lacteals – Specialized Lymphatic Capillaries Location Small intestinal villi Structure Same as typical lymphatic capillaries Functions Collect interstitial fluid rich in digested fats Drain lymph into lymphatic vessels Chyle

Lymph Trunks Locations Structure Functions Alongside large blood veins Similar to large blood veins Functions Receive lymph from lymphatic vessels Drain lymph into lymph ducts

Lymph Trunks Lumbar Trunk Intestinal Trunk Bronchomediastinal Trunk Subclavian Trunk Jugular Trunk

Figure 22.3

Figure 22.3

Lymph Ducts Location Structure Function Thoracic duct (left lymphatic duct) Right lymphatic duct Structure Similar to large blood veins Function Receive lymph from lymph trunks Drain lymph into subclavian veins

Lymphatic System Topics Components of the lymphatic system Functions of the lymphatic system Organization of lymphatic vessels Formation and flow of lymph Lymphatic organs

Formation of Lymph Lymph is formed when interstitial fluid drains into lymph capillaries

Brings back the 1 mmHg different between filtration / reabsorption Fig 21.07

Figure 22.4

Lymphatic Capillaries Arteries Blood Capillaries Interstitium Lymphatic Capillaries Lymphatic Vessels Lymph Nodes Lymph Trunks Lymphatic Ducts Subclavian Veins Lymph Flow

Lymph Flow Lymph flow aided by similar mechanisms as in the circulatory system: Milking action of skeletal muscle contractions Respiratory movements (pump) Valves that prevent backflow of lymph Vessel smooth muscle contraction

Lymph Drainage (Figure 22.1)

Lymphatic System Topics Components of the lymphatic system Functions of the lymphatic system Organization of lymphatic vessels Formation and flow of lymph Lymphatic organs

Lymphatic Organ Classification Primary Lymphatic Organs Immunocompetency Red bone marrow Thymus Secondary Lymphatic Organs Lymph nodes Spleen Lymphatic nodules ***

Thymus Gland Location Structure Function Mediastinum Bilobed; encapsulated; trabeculae (lobules) Cortex and medulla Contain T cells, dendritic and epithelial cells, macrophages Function Site of T cell maturation (positive selection)

Figure 22.5

Lymph Nodes Location Structure Functions Along lymphatic vessels Encapsulated; oval; trabeculae (compartments) Stroma and parenchyma (cortex + medulla) Contain lymphocytes and other immune cells Functions Receive lymph from afferent lymphatic vessels Filter foreign substances out of lymph Drain lymph into efferent lymphatic vessels

Figure 22.6

Spleen Location Structure Functions Left hypochondriac region between stomach’s fundus and diaphragm Structure Encapsulated (Stroma) Parenchyma: White pulp and Red pulp Functions Next slide

Figure 22.7

Spleen Functions Receives blood from splenic artery Phagocytoses pathogens Mounts immune response against pathogens Phagocytoses old blood cells Stores blood platelets Produces blood cells during fetal life

Lymphatic Nodules (Tissue) Locations GI tract, respiratory airways, urinary tract, and reproductive tract MALT (Peyer’s patches, tonsils, appendix) Structure Unencapsulated; oval Function “Sentinels” Mount immune response against foreign substances