Lymphatic System Overview

Lymphatic System Functions

• Transports lymphocytes and other immune cells
• Returns excess fluid from body tissues to the blood, maintaining blood volume

Lymphatic System Components

• Consists of lymph vessels, lymphatic tissues, and organs
• Lymph is fluid transported within the lymph vessels

Primary Lymph Structures

• Involved in lymphocyte maturation and formation
• Includes red bone marrow and thymus

Secondary Lymph Structures

• Houses immune cells
• Responsible for immune response initiation
• Includes lymph nodes, spleen, tonsils, and lymphatic nodules as well as mucosa-associated lymphatic tissue (MALT)

Characteristics of Lymph

• Some fluid from blood capillaries isn't reabsorbed
• Interstitial fluid enters capillaries where it becomes lymph

Lymph Components

• Consists of water, dissolved solutes, and small amounts of protein
• May contain cell debris, pathogens, or cancer cells

Lymphatic Capillaries

• Absorb interstitial fluid through small, closed-ended vessels
• Interspersed with most blood capillaries
• Absent in avascular tissues, red bone marrow, spleen, and CNS
• Slightly larger than blood capillaries, with no basement membrane
• Walls are overlapping epithelial cells with one-way flaps
• Lacteals are lymphatic capillaries in GI tract absorbing lipid-soluble substances

Cancer Metastasis

• Cancer cells travel, forming secondary tumors
• Cancer cells develop in new locations within the body
• Cancerous cells break away from a primary tumor
• Cancer cells are transported in the lymph

Lymphatic Vessels

• Vessels are fed by lymphatic capillaries
• Located near arteries and veins
• Valves prevent pooling and backflow

Lymph Movement

• The lymphatic system lacks a pump, relies on skeletal muscles, respiratory pumps, pulsation of nearby arteries, and rhythmic contraction of larger lymph vessel walls to move lymph
• Some vessels connect to lymph nodes for lymph filtration

Lymphedema

• Blockage of lymph system results in swelling
• Interstitial fluid accumulation due to obstructed lymphatic drainage
• Usually caused by obstruction, surgical removal of lymph nodes, spread of malignant tumors, scarring from radiation therapy, or trauma/infection
• Can be controlled with compression garments, exercise, and massage

Elephantiasis

• Extreme form of lymphedema
• Caused by filarial worms infecting the lymphatic system, occurs in southeast Asia/Africa

Red Bone Marrow

• Found between trabeculae of spongy bone
• Located in flat bones such as the skull, ribs, sternum, vertebrae, ossa coxae, and the head of the femur, etc
• Site of hematopoiesis (blood cell formation)
• T and B lymphocytes are formed
• T-lymphocytes migrate to the thymus to complete maturation

Thymus

• Involved in T-lymphocyte maturation
• Located in the mediastinum
• Larger in children than adults
• Grows until puberty, then gradually replaced by adipose tissue
• Outer cortex contains immature T-lymphocytes
• Inner medulla contains mature T-lymphocytes

Lymph Nodes

• Filter lymph and remove unwanted substances
• Small, oval, encapsulated structures along lymph vessel pathways
• Occur in clusters, filtering lymph from body regions
• Cervical nodes receive lymph from head and neck
• Axillary nodes receive lymph from breasts, axilla, and upper limbs
• Inguinal nodes receive lymph from pelvis and lower limbs

Lymph Flow Through Nodes

• Enters nodes through afferent vessels
• Creates pressure, pushing lymph out through a single exit vessel
• Lymph is monitored for foreign material
• Macrophages remove debris
• Lymphocytes may initiate an immune response
• Enlarged nodes can be palpated in neck and axilla

Hodgkin Lymphoma vs Non-Hodgkin Lymphoma

• Both:

  • Malignant neoplasms from lymph structures
  • Feature nontender, enlarged lymph nodes

• Hodgkin:

  • May also cause night sweats, fever, and weight loss
  • Occurs in young adults and people over 60
  • Can be cured with excision, radiation, and chemotherapy if localized

• Non-Hodgkin:

  • More common, aggressive, and multiple

Spleen

• The largest lymphatic organ, contains tissues of the spleen
• White pulp: clusters of T and B lymphocytes and macrophages around the central artery
• Red pulp contains erythrocytes, platelets, macrophages, and B-lymphocytes; stores erythrocytes and platelets

Splenectomy

• Surgical removal of the spleen
• May be required after a ruptured spleen (most common), or infection, cyst, tumor, blood disorder, or cancer
• May predispose to life-threatening infections

Tonsils

• Pharyngeal tonsil: called adenoids when enlarged
• Palatine tonsils and lingual tonsils

Tonsillitis and Tonsillectomy

• Acute tonsillitis: inflammation and infection of tonsils
• Palatine tonsils are most commonly affected
• Symptoms: reddened and enlarged tonsils, partial pharynx obstruction, fever, chills, sore throat, difficulty swallowing; caused by viruses or bacteria
• Persistent recurrent infections is chronic tonsillitis, may require surgical removal

Lymphatic Nodules

• Clusters of lymphatic cells with some extracellular matrix
• Not completely surrounded by connective tissue capsule
• Scattered nodules diffuse lymphatic tissue
• Found in every body organ, help defend against infection
• Groups together form larger structures called MALT

Mucosa-Associated Lymphatic Tissue (MALT)

• Located in GI, respiratory, genital, and urinary tracts
• Helps defend against foreign substances
• Peyer patches: collections of lymphatic nodules within the wall of the GI tract, especially in the ileum

Types of Immunity

• Two types of Immunity differ based on cells involved, specificity of cell response, mechanism of elimination of harmful sunstances, and response time

Body Defense

• Innate defenses guard against any pathogen
• Adaptive defenses (immunity) mount a response against a very specific target
• Innate defenses respond rapidly: species resistance, mechanical barriers, chemical barriers, natural killer cells, inflammation, phagocytosis, and fever
• Adaptive immunity is specific and develops slowly, carried out by lymphocytes
• Innate and adaptive immunity are distinct but work together

Innate Immunity

• Present at birth, protects against variety of substances (non-specific)
• No prior exposure to substances is necessary
• Includes barriers of the skin and mucosal membranes, nonspecific cellular and molecule internal defenses
• Responds immediately to potentially harmful agents

Adaptive Immunity

• Acquired and specific
• Response to antigen involves T and B-lymphocytes
• Responds to one specific foreign substance
• Takes several days to be effective

First Line of Defense: Mechanical Barriers

• Unbroken skin and mucous membranes prevent pathogen entry
• Includes hair, mucus, and sweat

Second Line of Defense: Chemical Barriers

• Highly acidic environment from gastric juice, or lysozyme in tears, kill many pathogens
• Interferons produced by cells infected by viruses induce nearby cells to produce antiviral enzymes and stimulate phagocytosis
• Complement activation stimulates inflammation, attracts phagocytes, and enhances phagocytosis

Natural Killer (NK) Cells

• Lymphocyte that defends against viruses and cancer by secreting perforins
• NK cells enhance inflammation

Inflammation

• Tissue response to pathogens characterized by heat, swelling, redness, and pain
• Vasodilation, blood volume increase, white blood cell invasion, blood clotting, and fibroblast appearance

Phagocytosis

• Neutrophils and monocytes (active phagocytes) leave the bloodstream at areas of injury (diapedesis)
• Attracted to injured area via chemotaxis
• Neutrophils engulf smaller particles, monocytes attack larger ones
• Monocytes become macrophages
• Removes foreign particles from the lymph

Fever

• Protection against infection by interfering with bacterial growth
• Fever reduces the amount of iron and nutrients available to pathogens
• Phagocytic cells attack with greater vigor when temperature rises

Innate Immunity Charcteristics

• Prevents entry of potentially harmful substances
• Responds nonspecifically to a range of harmful substances
• First line of defense is skin and mucosal membrane
• Second line: neutrophils, macrophages, dendritic cells, eosinophils, basophils, and NK cells

Immune System

• Antimicrobial proteins and interferons
• Interferons nonspecifically impede viral spread
• Leukocytes and virus infected cells produce IFNa and IFNβ- bind to neighboring cells and prevents function
• Triggers synthesis of enzymes that destroy viral nucleic acids, inhibit synthesis of viral proteins
• Stimulate NK cells to destroy virus infected cells T-lymphocytes and NK cells produce IFN, stimulates macrophages to destroy virus infected cells

Antimicrobial Proteins and Complement System

• Complement system: group of over 30 plasma proteins that works along with complement antibodies
• Identified with letter C and a number, synthesized by the liver, continuously released in inactive form
• Activation occurs by enzyme cascade, especially potent against bacterial infections

Inflammation (NsID)

• Immediate response to ward of unwanted substances
• Release of chemicals that initiate responses from injured tissue, basophils, mast cells, and infectious organisms
• Released chemicals include histamine, leukotrienes, prostaglandins, chemotactic factors

Vascular Changes Due to Released Chemicals

• Vasodilation
• Increased capillary permeability
• Increased endothelial expression of molecules for leukocyte adhesion

Leukocyte Recruitment

• Leukocytes release cytokines stimulating leukopoiesis in marrow
• Macrophages release pyrogens that induce fever

Delivery of Plasma Proteins to Site

• Immunoglobulins, complement, clotting factors, and kinins are delivered
• Clotting proteins form clots that wall off microbes
• Kinins stimulate pain receptors, increase capillary permeability

Effects of Inflammation

• Fluid (exudate) moves from blood to injured or effected area, contains proteins, immune cells to eliminate pathogens, promote healing
• Vasodilation brings more blood to area and increase capillary permeability
• Extravasted fluid is taken up by lymphatic capillaries, carries away debris while swelling results some fluid in interstitial space

Resolution of Inflammation

• The inflammatory response slows within 72 hours
• Macrophages eat bacteria, damaged host cells, and dying neutrophils
• Tissue repair begins as fibroblasts form new connective tissue

Cardinal Signs of Inflammation

• Redness from increased blood flow
• Heat from increased blood flow and increased metabolic activity
• Swelling from increased fluid loss from capillaries
• Pain from stimulation of pain receptors (compression (extra fluid) and chemical irritants)
• Loss of function with severe pain and swelling
• Duration of acute inflammation 8-10 days

Fever (NsID - pyrexia)

• Body temperature above normal (by 1°C or more)
• Results from the release of pyrogens from immune cells or infectious agents

Fever Events

• Pyrogens circulate through blood and target the hypothalamus
• The hypothalamus releases prostaglandin E2 increasing the temperature set point causing fever
• Fever stages: onset, stadium, and defervescence

Fever Benefits

• Inhibits reproduction of bacteria and viruses
• Promotes interferon activity
• Increases adaptive immunity
• Accelerates tissue repair
• Increases immune cell migration from blood
• Low-grade fever is recommended to be left untreated

Risks with High Fever

• Potentially dangerous
• Changes in metabolic pathways and denaturation of proteins
• Possible seizures
• Irreversible brain damage above 41°C (106°F)
• Death is likely above the temperature of 42.8°C (109°F)

Pus and Abscess

• Pus is an exudate that contains destroyed pathogens, dead leukocytes, macrophages, cellular debris
• Removed by lymphatic system or through skin
• If not completely cleared, can form an abscess
• Pus is walled off by collagen fibers and removed by surgical intervention

Chronic Inflammation

• Inflammation continues for over 2 weeks
• Characterized by macrophages and lymphocytes, not neutrophils
• Can occur from overuse injuries (shin splints, tennis elbow), when acute inflammation is unable to clear the pathogen, or due to autoimmune disorder
• May lead to tissue destruction and scar tissue formation

Adaptive Immunity

• Involves specific lymphocyte responses to an antigen
• Contact with antigen causes lymphocyte proliferation
• The immune response consists of lymphocytes and their products
• Takes longer to respond than innate immunity; develops over days
• Considered the body's third line of defense

Branches of adaptive immunity

• Cell-mediated immunity involving T-lymphocytes
• Humoral immunity involving B-lymphocytes, plasma cells and antibodies

Immune System Disorders

• Immune system lacks tolerance for a specific antigen
• Initiates immune response as if cells were foreign
• Rheumatic heart disease, type 1 diabetes, multiple sclerosis are examples

T-Lymphocytes and B-Lymphocytes

• T-lymphocytes are cells of cell mediated immunity
• B-lymphocytes are cells of humoral immunity

Organ Transplants

• Individuals are tested prior to donation for MHC antigens and ABO group
• The major histocompatibility complex (MHC) cell surface proteins allow acquired immune system to recognise foreign

Major Histocompatibility Complex (MHC)

• Tags antigens derived from pathogens and displays them on the cells surface for recognition by the appropriate T cells
• No exact duplicate MHC molecules
• Components of innate and adaptive immunity attempt to destroy transplanted tissues
• Recipients take immunosuppressant drugs

Lymphocyte Formation

• T-lymphocytes originate in red bone marrow and migrate to the thymus as pre-T lymphocytes to complete maturation
• Immunocompetent T-lymphocytes can bind antigens and respond to them
• Naive T-lymphocytes haven't yet been exposed to antigens
• Regulatory T-lymphocytes (T-Regs) are CD4+ cells formed from T cells that find self antigens and inhibit immune response
• Some tumors foster T-reg proliferation, and certain cancer treatments try to inhibit tumor T-reg

Immunoglobulins

• Antibodies are Immunoglobulins (Ig) proteins produced against a particular antigen
• Antibodies tag pathogens for destruction by immune cells
• Offer defense against viruses, bacteria, toxins, and yeast spores
• Soluble antigens are combated by humoral immunity

Antibody Functions: Neutralization

• The antibody physically covers antigenic determination of pathogen
• The pathogen is ineffective in establishing infection
• Covers regions of a virus that are used to bind to a cell receptor

Antibody Functions: Agglutination

• Antibodies cross-link antigens of foreign cells causing clumping
• Effective against bacterial cells

Antibody Functions: Precipitation

• Antibodies cross-link circulating antigens forming a complex that becomes insoluble and precipitates out of body fluids
• Precipitated complexes are engulfed and eliminated by phagocytes

Antibody Functions: Complement Fixation

• IgG and IgM can bind complement for activation (classical complement activation)

Antibody Functions: Opsonization

• Certain antibody classes make a cell more likely to be phagocytized

Antibody Functions: NK Activation

• IgG triggers NK cells to release cytotoxins
• This process creates cell mediated cytotoxicity (ADCC)

Types of Antibodies

• There are give major types of antibodies that constitute the gamma globulin fraction of the plasma
• IgG antibodies are in tissue fluid and plasma, defend against viruses, toxins, and bacterial cells, and activate complement
• IgA antibodies are in exocrine secretions and defends against foreign substances
• IgM antibodies are primarily in plasma, activates complement, and reacts with blood cells during transfusions
• IgD antibodies are on the surface of most B lymphocytes and functions in B cell activation
• IgE antibodies are in exocrine gland secretions and promote allergic reactions

Practical Classification of Immunity

• Naturally acquired active immunity is acquired by exposing the body to an antigen
• Artificially acquired active immunity is acquired by getting vaccines
• Artificially acquired passive immunity is acquired by receiving a gamma globulin
• Naturally acquired passive immunity is acquired during pregnancy when a mother passes antibodies to her fetus

Hypersensitivities

• Are abnormal and exaggerated immune responses to an antigen
• Acute hypersensitivity: reactions occur within seconds (anaphylactic)
• Subacute hypersensitivity: occur within 1-3 hours, both involve humoral immunity
• Delayed hypersensitivity: occur in 1-3 days, involve cell mediated immunity

Vaccinations

• Introduces weakened or dead organisms, or organism components
• Stimulates the immune system to develop memory B-lymphocytes
• Provides a relatively safe means for initial exposure to a microorganism
• If exposed later in life, will trigger a secondary response
• The immune system response predominantly comes from the humoral branch
• May provide either lifelong immunity or require a booster shot

Gametogenesis

• Defined as male and female reproductive systems consisting of a series of glands and tubes to produce and nurture sex cells, and transport them to the site of fertilization

Sperm and Oocytes

• Sperm cells are male sex cells
• Oocytes are female sex cells

Sperm Cell Formation

• In the male embryo, undifferentiated spermatogenic cells turn into spermatogonia; each contains 46 chromosomes
• Primary spermatocytes are formed during spermatogenesis when spermatogonia enlarges
• Secondary spermatocytes with 23 chromosomes divide from primary spermatocytes by meiosis
• The secondary spermatocytes divide again to form spermatids, each of which matures into a sperm cell

Oocyte Formation

• During prenatal development, small groups of cells form millions of primordial follicles; each has a primary oocyte and follicular cells
• The primary oocytes begin to undergo meiosis early on, but then are halted until puberty.
• 400-500 are released from the ovary during the reproductive life of the female.

Oogenesis

• At puberty, oocytes are stimulated to continue meiosis
• During meiosis, a primary oocyte matures into a secondary oocyte
• A second cytoplasmic division results in an egg cell and another polar body

Pregnancy

• Continuous process of individual changes from one life phase to another, consisting of an increase in size (growth)
• The prenatal period includes the time from fertilization to birth
• Postnatal period includes the time from birth to death
• Pregnancy is the presence of offspring developing in the uterus

Fertilization

• Sperms erode away the corona radiata and zona pellucida surrounding the secondary oocyte with the acrosomal enzyme and one sperm cell penetrates the egg cell membrane
• Penetration prevents the entry of subsequent sperm cells
• Fusion of egg and sperm nuclei is completed, resulting in a diploid zygote

Stages of Prenatal Development

• The zygote undergoes cleavage (mitosis)
• The dividing mass of cells (morula) moves down the uterine tube to the uterus, where a stage called the blastocyst implants in the lining of the uterus, marking the start of the embryonic stage
• The offspring is called an embryo during the first eight weeks and then a fetus

Pregnancy Hormones

• The trophoblast secretes human chorionic gonadotropin (hCG) to maintain the corpus luteum and thus maintain the uterine lining and the pregnancy.

Key Pregnancy Hormones

• Secreted by the trophoblast are human chorionic gonadotropin (hCG), which are sustained until the placenta is developed for hormone prodution to support pregnancy
• Also secreted by the placenta are placental lactogen for mammary gland development and secretion of estrogen

Fetal Stage

• Begins at the end of eighth week and lasts until birth.
• Structures grow and mature, and the bones ossify Maternal feeling of fetal movement occurs near the fifth month of gestation alongside hair appearance
• Last stage of fetal growth: brain cells form rapidly and organs grow and mature as the fetus increases in size.

Birth Process

• Pregnancy terminates after thirty-eight weeks
• The aging Placenta produces less progesterone which can stimulate the synthesis of prostaglandins, which can initiate labor
• Stretch of uterine tissues releases oxytocin to stimulates uterine contraction
• Fetal head stretches the cervix and stimulates positive feedback for stronger contractions and releases additional oxytocin.
• Muscles work together force baby through the birth canal, followed by placenta via uterine contractions (afterbirth)

Postnatal Period

• Mother and newborn undergo physical and physiological changes

Milk Production

• The mammary glands produce large qualities of milk after childbirth
• Colostrum (first milk) is a watery fluid that is rich in proteins and antibodies
• Sucking action of the infant releases oxytocin which triggers the release of milk

Neonatal Period

• Starts at birth and lasts for four weeks
• Forceful first breath inflates lungs for the first time

Newborn

• Surfactant in a full-term newborn reduces alveolar surface tension
• Newborns live off their fat stores for two to three days followed by mother's milk
• The newborn is susceptible to dehydration due to homeostatic mechanisms that are unable to fully conserve water

Common Elements: Male and Female Repro

• Possess primary repro organs (gonads) --Ovaries: female gonads -- Testes: male gonads
• Gonads produce sex cells (gametes) and unite during fertilization
• Gamete union initiates new individual development

Sex Hormones

• Gonads Produce sex hormones
• Affects the maturation development and activity of repro organs
• Both sexes possess accessory reproductive organs -- Female: Repro ducts bring gametes to site of fert -- Male: Repro ducts bring gametes closer body exterior

Puberty

• Occurs during adolescence -- Develop external sex characteristics
• • Gametes become mature -- Gonads start secreting sex horones

Hormones

• Initiated when hypothalamus secretes GnRH
• GnRH stimulates anterior pit secretes two hormones: FSH LH
• The gonads begin producing significant levels of sex hormones which initiates gamete and sexual maturation

Gametes

• Prod by males and females Female prod releases a single gamete monthly (oocyte)
• Male prod large number: -- 100 million 1 day Are Stored for only short time if not released from the body Reabsorbed by body

Menopause

• Occurs once women have no cycles for one year Not associated with pregnancy or medical
• Occurs at 45-55 age range
• The ovaries produce negligible or not estrogen or progesterone production to grow or sustain the linings of the uterus
  • End result-no menstruation

Tubal Pregnancy

• Occurs when fertilized oocytes implant in regions of the uterus Fertilization in uterine tube
• Embryo viable for only 8 wks (not sustainable development)

Endomitosis

• Occurs when endometrial tissues becomes displaced and implanted on external surfaces within the abdominopelvic cavity
• Causes chronic pain as tissue cannot be expelled normally
• Endometrium is sensitive to hormones

Cervial Cancer

• HPV is a leading risk factor for malignancy in female repro sys Vaccine for the 4 most common strands are recommended

Pap tests

• Detects abnormal cellular development in cervical Performed scraping cell edge to be exam Invasive or cancerous cell are removed with hysterectomy

Mammary Glands

Release Breast Milk Occurs as result interaction from both intenaland external Starts shortly after partituion

Prolactin

• Produced in the anterior Pit Responsible in milk production Results with increase Mammary gland forming greater alveriols

Oxytocin

• Results in Hypothalamus causing ejection Response from breast feeding

Pregnancy Prevention

• Abstinence (100%)
• Rhythm (25% risk): by timing intercourse to when ovulation is least likely
• Pulling Out (19% risk): pulling before ejaculation
• Barriers methods : Condoms

Lactation

• Hypthothmically suppresses FSH and LH to inhibit conception
• Intrauterine Devices: Mech device inserts into utrus

Sexual Regulation

• Hormone production -- Hypothal releases GnRH (1.stim)
• ( 2.stim) Releases FSH and LH

3. FSH and LH stimulate spermatogenises LH releases interstitial for testosterone FSH release testerone for hight in testis where is bind for cell activity

Testerone

4. Testerone Faciliates spermagenesis, blocks GnRH, pituitary sensitives and produces negative back effect
5. Stertoial cells releases cell count (inhibin), producing more count decreasing and blocks secretions
6. Testo facilitates libido development, develops sex and axillary hair, facial hair and voice