BIOL 2020: Anatomy and Physiology 2 Exam 3 Study Notes

*Underlined words is what was blank in the notes* Ch. 21, 22, 25 Tennessee Tech University (TTU) Dr. Hall A&P2

Ch. 21 Lymphatic System

A body system with organs and vessels

Ch.21 Functions of the Lymphatic System

Fluid recovery, Immunity, Lipid absorption

Ch. 21 Fluid Recovery

• Blood capillaries reabsorb 85%

• The remaining 15% (2-4 L/day) is absorbed by lymphatic capillaries

Ch. 21 Immunity

• Excess filtered fluid picks includes foreign cells and chemicals from the tissues

  • Passes through the lymph nodes where immune cells stand guard against foreign matter

  • Activates a protective immune response

Ch. 21 Lipid Absorption

• Lacteals in small intestine absorb dietary lipids that are not absorbed by the blood capillaries

Ch. 21 Components of the Lymphatic System

Lymph, Lymphatic vessels, Lymphatic tissues, Lymphatic organs

Ch. 21 Lymph

• Clear fluid resulting from uncovered blood plasma. Like plasma, but with fewer proteins/nutrients

Ch.21 Lymphatic Vessels

• Transport the lymph

• Pathway:

  • Lymphatic capillaries → Lymphatic vessels → Lymphatic trunks → Collecting ducts → Subclavian veins

Ch.21 Lymphatic Tissues

• Dense populations of lymphocytes and macrophages within organs and tissues

Ch.21 Lymphatic Organs

• Immune cells are especially concentrated in these organs

• True organs enclosed in connective tissues (e.g. spleen and thymus)

Ch.21 Lymphatic Capillaries

• Embryonic origin of lymphatic vessels is from the veins so they have similar structure to blood vessels

• Capillary wall is endothelial cells overlapping each other like roof shingles

• Gaps between cells are large enough to allow bacteria and cells to enter

• Like veins - lower pressure requires valves for one way flow

Ch. 21 Three layers of the larger vessels

Tunica Interna, Tunica Media, Tunica Externa

Ch.21 Tunica Interna

Endothelium and valves

Ch. 21 Tunica Media

Elastic fibers and smooth muscle

Ch. 21 Tunica Externa

Thin outer layer of connective tissue

Ch. 21 Larger Lymphatic Vessels

• 3 layers

• Converge into larger and larger vessels

• Lymph nodes are typically found along the vessels

Ch. 21 Drainage and Flow Collecting Ducts

• Right lymphatic duct

• Thoracic duct

Ch.21 Right lymphatic duct

• Receives lymph from right arm, right side of head and thorax

• Empties into right subclavian vein

Ch.21 Thoracic duct

• Receives lymph from everywhere else

• Empties into left subclavian vein

Ch.21 Drainage and flow

• 6 lymphatic trunks drain major portions of body

• All lead to 2 collecting ducts: right lymphatic duct & thoracic duct

• Moved along by rhythmic contractions of lymphatic vessel smooth muscle

  • Also moved by same mechanisms as venous return (e.g. skeletal muscle pump, thoracic pump, etc.)

Ch. 21 Lymphatic Tissues (i.e. groups of immune cells)

• Lymphatic (lymphoid) tissue- aggregations of lymphocytes in the connective tissues of mucous membranes and various organs

• Diffuse lymphatic tissue- simplest form

  • Lymphocytes are scattered (not clustered)

  • Prevalent in body passages open to the exterior

    • Respiratory, digestive, urogential tract

• Lymphatic modules (follicles)

  • Dense masses of lymphocytes and macrophages that congregate in response to pathogens

  • Not the same thing as lymph nodes

Ch. 21 Primary Lymphatic Organs

• Sites where T and B cells attain immunocompetence (able to recognize and respond to antigens)

  • Includes the red bone marrow and thymus

Ch. 21 Secondary Lymphatic Organs

• Locations where immunocompetent cells reside

  • Lymph nodes, tonsils, and spleen

Ch. 21 Lymph Nodes

• Most numerous lymphatic organ

  • Approx. 450 in typical young adults

  • Harbor lymphocytes which cleanse the lymph of toxins, pathogens

• Concentrated in various locations

  • Cervical, axillary, thoracic, abdominal, intestinal, mesenteric, inguinal

  • Lymphadenitis: swollen, painful node responding to infection or high antigen load

Ch.21 Tonsils

• Located at the entrance to the pharynx

  • Guard against ingested or inhaled pathogens

  • Have deep pits called tonsillar crypts

    • Lined with lymphatic nodules

• Palatine tonsils

  • Back of oral cavity, most often infected (tonsillitis) and used to be frequently removed (tonsillectomy)

• Lingual tonsils - behind the tongue

• Pharyngeal tonsils (adenoids)

  • Single tonsil on wall of nasopharynx

Ch. 21 Tissues in Spleen

Red pulp and White pulp

Ch.21 Red Pulp

• Sinuses filled with erythrocytes

• Old, worn RBCs burst (lyse) in this tissue and are recycled by macrophages in the white pulp

Ch. 21 White Pulp

• Collections of lymphocytes and macrophages surrounding small branches of the splenic artery

• Monitors blood for foreign antigens

• Harbors WBCs for release when needed

• Macrophages recycle lysed RBCS

Ch. 21 Immune System

• Not an anatomical system

• A collection of proteins and cells

• Cells often concentrate in lymphatic organs and tissues but are distributed through all body systems

• No anatomy of its own - all physiology

• Function is to defend the body from foreign material including bacteria, fungi, parasites, viruses, toxins, allergens as well as cancer cells (which aren’t foreign)

• Pathogen- agents capable of producing disease

Ch.21