Compendium 10 Flashcards
Functions of the lymphatic system
Fluid balance
Fat absorption
Defense
What organs / structures make up lymphatic system
Lymph Lymph vessels Lymphatic tissue Lymphatic nodules Lymph nodes Tonsils Spleen (largest lymphatic organ) Thymus
Describe lymph
Water plus solutes from plasma such as ions, nutrients, gases, proteins and solutes from cells such as hormones, enzymes, wastes
Called lymph once picked up by lymphatic system which has to occur else would cause fluid accumulation which could be deadly
Returns to circulatory system via veins
Describe lymphatic vessels
Carry lymph away from tissues towards heart
Lymph flow is strictly one way
Formed by lymphatic capillaries which are highly permeable (no basement membrane), cells contain one way valves, found in all body parts except NS, bone, avascular tissue, often anchored to other structures in CT by collagen fibres which ensures they always stay open
Smallest type= blind end capillaries in tissues
Has 3 layers: epithelium, smooth muscle, CT
Smooth muscle contractions and specialised pacemaker cells in smooth muscle help push lymph along
Describe lymph nodes
Round filtration bodies found along vessels and are made of lymphoid tissue
Only structures to filter lymph
Remove substances via phagocytosis or stimulate lymphocytes to proliferate and initiate an immune response
Cancer cells often migrate to lymph nodes are trapped there and proliferate before moving into circulatory system
Contain afferent vessel that carries lymph into node and efferent vessels that carry lymph out
Organised into cortex and medulla with dense CT capsule surrounding it (encapsulated)
Become enlarged during infection as substances trapped in nodes
Describe lymphatic trunks
Group of vessels merge to form a trunk
Named based on area of body in which they drain:
Jugular- head and neck
Subclavian- upper limbs, thoracic wall, mammary glands
Bronchomediastinal- thoracic organs, deep thoracic wall
Intestinal- abdominal organs
Lumbar- lower limbs, organs in pelvis
Connect to large veins in thorax and deposit lymph back into venous circulation of will merge to form ducts
Describe lymphatic ducts
Drain tissues of body and move lymph into major veins
Right lymphatic duct- drains right side of head, right upper limb, right thorax
Thoracic duct- remainder of body
Composition of lymphatic tissue and organs
Contain lymphocytes, macrophages, reticular cells and dendritic cells- mostly lymphocytes (B and T cells) to provide protection
Fine network of reticular fibres produced by reticular cells which anchor cells and act as filter to trap microorganism snd other particles
Can be encapsulated by CT or may not be
Describe lymphatic tissue and lymphatic nodules
Diffuse lymphatic tissue: dispersed lymphocytes, macrophages, reticular cells that blend with other tissues (found in every body organ)
Lymphatic nodules: denser aggregations, numerous in loose connective tissue of digestive, respiratory, urinary, reproductive systems (usually surrounded by diffuse lymphatic tissue)
Describe tonsils
Large groups lymphoid tissue in nasopharynx and oral cavity
Provide protection against bacteria and other harmful substances entering nose or oral cavity
Form ring around border between oral cavity and pharynx
Three different sets: palatine, pharyngeal, lingual
Non-encapsulated- covered by squamous epithelium which is highly folded so it can trap bacteria so when it reaches tonsils it can be destroyed
Describe spleen
Can increase in size with age and disease
Contains medial hilum where splenic artery and vein as well as some lymphatic vessels enter
Blood enters through artery is filtered and then leaves via vein
Divided into two parts:
Red pulp- associated with veins, makes up 75% inner part of spleen, fibrous network of macrophages and RBCs
White pulp- associated with arteries, makes up 25% inner part, lymphatic tissue
List functions of the spleen
Monitor blood, detect and respond to foreign antigens by initiating immune response
Destroy defective RBCs
Regulates blood volume
Stores RBCs
Can live without spleen but might be more prone to infections
Describe thymus
Located in superior mediastinum Each lobe surrounded by CT capsule which extends into thymus gland and divides thymus into lobules which is further divided into outer cortex and inner medulla Cortex contains most lymphocytes Site of maturation of T cells Also has endocrine functions
What are pathogens
Foreign agents that introduce nonself proteins into body that are called antigens
Antigenic receptors on T and B cells recognise foreign proteins as not being self so aims to remove them
What is immunity
Ability to resist damage to foreign substances and internal threats
External threat= bacteria, fungi, etc.
Internal threat= cancer cells
Two categories:
Innate/nonspecific: recognise any pathogen and fight it
Adaptive/specific: recognise certain pathogens and initiate response
Describe innate / nonspecific immunity
Present at birth
Has no memory- each time body is exposed to substance the response is the same
Provides immediate protection from pathogens and antigens
Involves first and second line of defense
Innate immunity: describe first line of defense
Are physical barriers
Skin Mucous membranes Salina Tears Acid in stomach, vagina, urinary tract Urine flushes through urinary passageways Cilia
Innate immunity: second line of defense
Involves white blood cells, chemical mediators, inflammation, fever
Innate immunity: second line of defense- white blood cells
Produced in bone marrow and lymphatic tissue
When tissue is damaged it releases chemicals that attract WBCs which can ingest antigens via phagocytosis
Also produce chemicals that attract other immune cells to are
Most important are neutrophils (first to arrive) and macrophages
Also basophils, natural killer cells, eosinophils
Innate immunity: second line of defense- chemical mediators
Promote inflammation and phagocytosis
Inflammation e.g. Histamine
Cytokines: secretes by one cell and stimulate neighbouring cell to respond, regulate intensity and strength of immune response
Complement: stimulate lysis (destroy) invading pathogens
Interferons: anti-viral activity
Innate immunity: second line of defense- inflammation
Local tissue response to damage
Aims to rid body of debris and pathogens and to prevent further damage or entry
Four features: redness (increased blood flow), heat (increased blood flow), swelling (capillaries become leaky/more permeable so fluid goes to damage that contains WBCs) and pain (increase fluid stimulated pain receptors, also chemicals released by cells can stimulate)
Steps:
1) bacteria enters tissue
2) tissue damage occurs
3) chemical mediators are released causing increased vascular permeability, increased blood flow and chemotaxis (signal to receive WBCs)
4) increased number WBCs and chemical mediators to tissue damage site
5) bacteria contained, destroyed and phagocytosed
6) if bacteria gone then tissue repair begins
7) if bacteria remain additional chemical mediators activated
Innate immunity: second line of defense- fever
Generalised response to tissue damage and infection
Can cause macrophages to release chemicals
Body temp and normally high which increases some antimicrobial substances, decrease microbial growth, increase body reactions to help repair tissue
Can also cause aching due to toxins released by body from bacteria or from dehydration
Describe adaptive / specific immunity
Can recognise a particular substance and has ability to remember substance for more rapid responses in subsequent exposures
Acquired during life time, depending on exposure
Fight invaders once innate system over run
Mediated by lymphocytes- T and B cells
Lymphocytes will become activated to initiate an immune response which will involve:
Helper T cells (cell mediated and anti body mediated)
Effector (killer/cytotoxic) T cells (cell mediated)
B cells (anti body)
Two processes: cell mediated and anti body mediated
Adaptive immunity: cell mediated immunity
T lymphocytes include: helped T cells and cytotoxic T cells)
Specific cytotoxic T cells become activated by specific antigens and will then bind to that antigen when it is presented to it
Cytotoxic T cells will not react until it is co stimulated by helper T cell which will release chemicals to tell cytotoxic T cell to react
Activated cytotoxic T cells will divide, most daughter cells will go and kill pathogen or become memory cells
Pathogens killed in various ways like making holes in cell wall, causing cells to explode, etc.
Adaptive immunity: antibody mediated immunity
Involves B cells
Specific B cell recognises specific antigen and will bind to receptor on that antigen and will then ingest it
Also requires co stimulation by a helper T cell
B cells will divide to form:
Plasma cells- make antibodies to kill pathogens by inactivating antigens by binding to them, bind antigens together or facilitate phagocytosis but attracted macrophages
Memory B cells - ensure faster response
Describe memory responses
Primary response: when B cell first activated by antigen and proliferates to produce antibodies and memory cells (long response, occurs with vaccination)
Secondary response: occurs during later exposure to same antigen - memory cells divide rapidly to form plasma cells and antibodies as well as additional memory cells
How can adaptive immunity be acquired
Active immunity: immunity provided by individuals own immune system
Natural- antigens introduced through natural response
Artificial- antigens deliberately introduced in cabinet
Passive immunity: immunity transferred from another person or an animal
Natural- antibodies from mother transferred across placenta to child or through milk
Artificial- antibodies produced by another person or an animal are injected (no memory)
