BIOH122 Human Biological Science 2 Session 7 Lymphatic System & Immune System Bioscience Department Endeavour College of Natural Health endeavour.edu.au
Session Plan o Functions and Structure of the lymphatic system o Lymphatic vessels and Lymph Flow o Lymphatic organs and tissues Primary lymphatic organs Secondary lymphatic organs and tissues o Immune System Overview Innate Immunity :1 st Line of Defence Endeavour College of Natural Health endeavour.edu.au 2
Functions and Structure of the lymphatic system Endeavour College of Natural Health endeavour.edu.au 3
Lymphatic System o The lymphatic system contributes to homeostasis by draining interstitial fluid as well as providing the mechanisms for defence against disease. o Functions: Drains excess interstitial fluid: Lymphatic vessels drain excess interstitial fluid from tissue spaces and return it to the blood. Transports dietary lipids: Lymphatic vessels transport lipids and lipid-soluble vitamins (A, D, E, and K) absorbed by the gastrointestinal tract. Carries out immune responses: Lymphatic tissue initiates highly specific responses directed against particular microbes or abnormal cells. Endeavour College of Natural Health endeavour.edu.au 4
Lymphatic System o Structure: The lymphatic system consists of Lymph: the fluid Lymphatic vessels: transport the lymph Lymphatic organs and tissue: made of specialized form of reticular connective tissue that contains large numbers of lymphocytes Red bone marrow: the site of lymphocyte production o Interstitial fluid and lymph are very similar. o Their major difference is location. Endeavour College of Natural Health endeavour.edu.au 5
Lymphatic System Endeavour College of Natural Health endeavour.edu.au 6
Lymphatic vessels and Lymph Flow Endeavour College of Natural Health endeavour.edu.au 7
Lymphatic Vessels o Lymph capillaries: Lymphatic vessels begin as blindended lymph capillaries in tissue spaces between cells. o Lymphatic vessels: Lymph capillaries merge to form larger vessels, called lymphatic vessels, which convey lymph into and out of structures called lymph nodes o Lymph trunks: Lymphatic vessels exit lymph nodes in a particular region of the body, they unite to form lymph trunks o Lymph Ducts: Lymph passes from lymph trunks into two main channels, the thoracic duct and the right lymphatic duct, and then drains into venous blood. Endeavour College of Natural Health endeavour.edu.au 8
Lymphatic Capillaries o Structure: slightly larger diameter than blood capillaries overlapping endothelial cells which work as one-way valves for fluid to enter the lymphatic capillary when tissue pressure is high. o Anchoring filaments: Attached to the lymphatic capillaries, contain elastic fibers Attach endothelial cells to surrounding tissue and Keep tube from collapsing under outside pressure Endeavour College of Natural Health endeavour.edu.au 9
Lymphatic Capillaries Endeavour College of Natural Health endeavour.edu.au 10
Lymphatic Capillaries o Location: throughout the body along the systemic circulation o Exception: not present in avascular tissue (cartilage, epidermis and cornea), the central nervous system, portions of the spleen, and red bone marrow. o Lacteals: specialized lymphatic capillaries in the villus of the small intestine, transport digested fats from the small intestine into the blood. Endeavour College of Natural Health endeavour.edu.au 11
Lymph Trunks o Lymph trunks: lymphatic vessels exit lymph nodes in a particular region of the body, they unite to form lymph trunks. Lumbar trunks: drain lymph from the lower limbs, the wall and viscera of the pelvis, the kidneys, the adrenal glands, and the abdominal wall. Intestinal trunks: drains lymph from the stomach, intestines, pancreas, spleen, and part of the liver. Broncho mediastinal trunks: drain lymph from the thoracic wall, lung, and heart Subclavian trunks: drain the upper limbs Jugular trunks: drain the head and neck. Endeavour College of Natural Health endeavour.edu.au 12
Lymph Ducts o Lymph Ducts: Lymph passes from lymph trunks into two main channels, the thoracic duct and the right lymphatic duct, and then drains into venous blood. o The thoracic duct: is the main collecting duct of the lymphatic system begins as a dilation called the cisterna chyli. receives lymph from the left side of the head, neck, and chest, the left upper extremity, and the entire body below the ribs. drains lymph into venous blood via the left subclavian vein. o The right lymphatic duct: Receives lymph from the upper right side of the body It drains lymph into venous blood via the right subclavian vein. Endeavour College of Natural Health endeavour.edu.au 13
Lymph Trunks and Ducts Endeavour College of Natural Health endeavour.edu.au 14
Lymph Trunks and Ducts Endeavour College of Natural Health endeavour.edu.au 15
Formation and Flow of Lymph o Lymph: The excess filtered fluid (about 3 litres per day) in interstitial space that drains into lymphatic vessels o Components: Similar to interstitial fluid o Sequence of Lymph flow: 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) o Pumps: Respiratory and muscular pumps promote flow of lymphatic fluid Endeavour College of Natural Health endeavour.edu.au 16
Formation and Flow of Lymph Fluid and proteins escaping from vascular capillaries is collected by lymphatic capillaries and returned to the blood Endeavour College of Natural Health endeavour.edu.au 17
Lymphatic organs and tissues Endeavour College of Natural Health endeavour.edu.au 18
Lymphatic Organs and Tissues o Widely distributed throughout the body o Primary lymphatic organs provide environment for stem cells to divide and mature into B and T lymphocytes Red bone marrow gives rise to mature B cells Thymus is the site where pre-t cells from red marrow mature o Secondary lymphatic organs and tissues site where most immune responses occur Lymph nodes Spleen Lymphatic nodules/follicles Endeavour College of Natural Health endeavour.edu.au 19
o Red bone marrow: o Location: Red Bone Marrow In flat bones and the epiphyses of long bones of adults o Function: Site for Pluripotent stem cells differentiation: in red bone marrow stem cells give rise to mature, immunocompetent B cells and to pre-t cells Endeavour College of Natural Health endeavour.edu.au 20
Thymus Gland o Thymus Gland: o Location: Between the sternum and the aorta o Structure: Large organ in infants (70g) but atrophied in old age (3g) 2 lobed organ: Capsule and trabeculae divide it into lobules Each Lobules has Cortex and Medulla o Function: Cortex: proliferation and maturation of Immature T cells (pre-t cells) migrated from red bone marrow Medulla: Release of mature and immunocompetent T cells into blood to migrate to lymph nodes and other lymph organs Endeavour College of Natural Health endeavour.edu.au 21
Thymus Gland Endeavour College of Natural Health endeavour.edu.au 22
o Thymus Gland Cortex: consists of large numbers of T cells and scattered dendritic cells, epithelial cells, and macrophages. Immature T cells (pre-t cells): migrate from red bone marrow to the cortex of the thymus. They proliferate and begin to mature Dendritic cells: Are derived from monocytes assist the maturation process Epithelial cells: produces thymic hormones (thymosin) to aid in the maturation of T cells. Thymic macrophages: help clear out the debris of dead and dying cells o Medulla: consists of widely scattered, more mature T cells, epithelial cells, dendritic cells, and macrophages Site of release of mature and immunocompetent T cells Hassall s corpuscles: clusters of epithelial cells; sites of T cell death in the medulla Endeavour College of Natural Health endeavour.edu.au 23
Lymph Nodes o Lymph nodes: o Location: All along lymphatic vessels about 600 lymph nodes, scattered throughout the body, both superficially and deep, and usually occur in groups Large groups are present near the mammary glands and in the axillae and groin. o Structure: encapsulated Bean-shaped organs, Two parts: The stroma: supporting framework of connective tissue The parenchyma: functioning part Endeavour College of Natural Health endeavour.edu.au 24
Lymph Nodes o The Stroma is constituted by: Capsule: Outer cover of dense connective tissue that extends into the node Trabeculae: The capsular extensions that divide the node into compartments, provide support, and provide a route for blood vessels into the interior of a node o The Parenchyma is divided into 2 regions: Cortex: outer and inner Medulla Endeavour College of Natural Health endeavour.edu.au 25
Lymph Nodes Outer cortex: Consists lymphatic nodules/follicles called a Germinal center Germinal center contains B cells, Dendritic cells and macrophages This is the site for B cells proliferation and differentiation into antibody-secreting plasma cells Also the site for where memory B cells are presented with an antigen by dendritic cells Endeavour College of Natural Health endeavour.edu.au 26
Lymph Nodes o Inner cortex: Consists mainly of T cells and dendritic cells that enter a lymph node from other tissues. Site for T cells proliferation when dendritic cells present antigens to T cells. The newly formed T cells then migrate from the lymph node to areas of the body where there is antigenic activity. o Medulla: contains B cells, antibody producing plasma cells that have migrated out of the cortex into the medulla, and macrophages Endeavour College of Natural Health endeavour.edu.au 27
Lymph Nodes Lymph flow: One direction due to one way valves in afferent and efferent vessels Endeavour College of Natural Health endeavour.edu.au 28
o Function: o Acts as a filter Lymph Nodes Many afferent vessels : Few efferent vessels Slow flow Lymph flows through many lymph glands to increase exposure Within lymph glands macrophages destroy some foreign substances by phagocytosis and lymphocytes (B cells and T cells) bring about the destruction of others by immune responses. o Site of proliferation of Plasma cells (antibody secreting B cells) and T cells. Endeavour College of Natural Health endeavour.edu.au 29
Metastasis Through Lymphatic System o Metastasis: The spread of a disease from one part of the body to another. o A characteristic of malignant tumours cancer cells travel via blood or lymphatic system cells establish new tumours where they lodge o Secondary tumour sites: can be predicted by the direction of lymphatic flow from the primary site o Cancerous lymph nodes are enlarged, firm and nontender o Infected lymph nodes are enlarged but not firm and are very tender Endeavour College of Natural Health endeavour.edu.au 30
Spleen o Spleen: o Location: between the stomach and diaphragm o Structure: the largest single mass of lymphatic tissue measuring about 12 cm Endeavour College of Natural Health endeavour.edu.au 31
Spleen Endeavour College of Natural Health endeavour.edu.au 32
o Structure: Spleen o Hilum: Through it pass the splenic artery, splenic vein, and efferent lymphatic vessels. o Stroma: consists of capsule, trabeculae, fibers and fibroblasts o Parenchyma: White pulp: a lymphatic tissue (lymphocytes and macrophages) around branches of splenic artery. Red pulp: consists of venous sinuses filled with blood and splenic tissue (splenic cords) Endeavour College of Natural Health endeavour.edu.au 33
Spleen o Function: White pulp: Lymphatic tissue. B Cells, T Cells and macrophages perform immune function (similar to lymph node process ) Red pulp: consists of venous sinuses filled with blood and splenic tissue. Removal of ruptured worn out RBC. Storage of platelets. Endeavour College of Natural Health endeavour.edu.au 34
Lymphatic Nodules o Lymphatic Nodules/follicles: egg-shaped masses of lymphatic tissue that are not surrounded by a capsule o Location: scattered throughout connective tissue of mucous membranes Also known as mucosa-associated lymphoid tissue (MALT) o Large aggregations in specific parts: Peyer s patches: In the ileum of the small intestine Appendix Tonsils: form a ring at the top of throat Adenoids/pharyngeal tonsil: in the posterior wall of the nasopharynx Palatine tonsils: at the posterior region of the oral cavity, one on either side Lingual tonsil: at the base of the tongue Endeavour College of Natural Health endeavour.edu.au 35
o Immune system: Overview o Innate Immunity: Non specific resistance First line of defence Second line of defence Phagocytosis Inflammation Endeavour College of Natural Health endeavour.edu.au 36
Immune system: Overview o Immunity/resistance: is the ability to ward off damage or disease through our defences. o The two general types: o Innate (nonspecific) immunity: defences that are present at birth o Adaptive/acquired (Specific) immunity: refers to defences that involve specific recognition of a microbe once it has breached the innate immunity defences. o Susceptibility: Vulnerability or lack of resistance Endeavour College of Natural Health endeavour.edu.au 37
Innate Immunity: Non specific resistance Endeavour College of Natural Health endeavour.edu.au 38
Innate Immunity: Non specific o Innate resistance: Immediately effective to a large, though a finite number of antigens that have been coded for in our DNA over millennia. o Non Specific: Reactive against conserved features common in many pathogens (eg LPS of gram negative bacteria) resistance o Two integrated lines of defence The first line defence The second line defence Endeavour College of Natural Health endeavour.edu.au 39
The First Line of Defense Endeavour College of Natural Health endeavour.edu.au 40
First Line of Defense: Skin and Mucous Membranes o The first Line of defence: The external physical and chemical barriers provided by the skin and mucous membranes o Physical barriers: intact epidermis layer of the skin, mucous membranes and the lacrimal apparatus. o Chemical barriers: is localized on the skin, in loose connective tissue, stomach, and vagina. Endeavour College of Natural Health endeavour.edu.au 41
Skin and Mucous Membranes: Physical barriers o Epidermis: closely packed, keratinized cells, the outer epithelial layer of the skin o Physical barrier to the entrance of microbes o Periodic shedding of epidermal cells helps remove microbes o Mucous membranes: line body cavities, trap and filter microbes and foreign substances through viscous mucus mucus-coated hairs in nose cilia in upper respiratory tract Endeavour College of Natural Health endeavour.edu.au 42
Skin and Mucous Membranes: Physical barriers o Lacrimal apparatus of the eyes: manufactures and drains away tears in response to irritants Protects the surface of the eyeball Dilute microbes and keep them from settling on the surface of the eye. o Saliva: Produced by the salivary glands Washes microbes from the surfaces of the teeth and from the mucous membrane of the mouth, Reduces colonization of the mouth by microbes. Endeavour College of Natural Health endeavour.edu.au 43
Skin and Mucous Membranes: Physical barriers o Perspiration: flush microbes from the surface of the skin o Defecation and vomiting: expel microbes through Vigorous contraction of the smooth muscle of the lower gastrointestinal tract in response to some microbial toxins o Urine: Cleansing of the urethra to retard microbial colonization of the urinary system Endeavour College of Natural Health endeavour.edu.au 44
Skin and Mucous Membranes: Chemical barriers o Sebum: An oily substance secreted by Sebaceous glands of the skin The unsaturated fatty acids in sebum inhibit the growth of certain pathogenic bacteria and fungi Forms a protective acidic film over the surface of the skin (ph 3 5). o Lysozyme: is an enzyme component of tears, saliva, perspiration, nasal secretions, and tissue fluids Breaks down the cell walls of certain bacteria. Endeavour College of Natural Health endeavour.edu.au 45
Skin and Mucous Membranes: Chemical barriers o Gastric juice: Highly acidic (ph 1.2 3.0), produced by the glands of the stomach destroys many bacteria and most bacterial toxins, renders the stomach nearly sterile. o Vaginal secretions: Slightly acidic, which discourages bacterial growth. Move microbes out of the body in females. Endeavour College of Natural Health endeavour.edu.au 46
Readings and Resources o Tortora, GJ & Derrickson, B 2014. Principles of Anatomy and Physiology, 14th edn, Wiley. o Harris, P, Nagy, S & Vardaxis, N 2010, Mosby s Dictionary of Medicine, Nursing and Health Professions, 2nd edn, Mosby Elsevier. o Guyton, AC & Hall, JE 2011, Textbook of Medical Physiology, 12th edn, Saunders Elsevier. o Marieb, EN & Hoehn, K 2010, Human Anatomy and Physiology, 8th edn, Benjamin Cummings Pearson. o Moore, KL, Dalley, AF & Agur, AMR 2010, Clinically Orientated Anatomy, 6th edn, Lippincott, Williams & Wilkins. Endeavour College of Natural Health endeavour.edu.au 47
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