Compendium 10

Question 1

Functions of the lymphatic system

Answer 1

Fluid balance
Fat absorption
Defense

Question 2

What organs / structures make up lymphatic system

Answer 2

Lymph
Lymph vessels
Lymphatic tissue
Lymphatic nodules
Lymph nodes
Tonsils
Spleen (largest lymphatic organ) 
Thymus

Question 3

Describe lymph

Answer 3

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

Question 4

Describe lymphatic vessels

Answer 4

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

Question 5

Describe lymph nodes

Answer 5

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

Question 6

Describe lymphatic trunks

Answer 6

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

Question 7

Describe lymphatic ducts

Answer 7

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

Question 8

Composition of lymphatic tissue and organs

Answer 8

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

Question 9

Describe lymphatic tissue and lymphatic nodules

Answer 9

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)

Question 10

Describe tonsils

Answer 10

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

Question 11

Describe spleen

Answer 11

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

Question 12

List functions of the spleen

Answer 12

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

Question 13

Describe thymus

Answer 13

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

Question 14

What are pathogens

Answer 14

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

Question 15

What is immunity

Answer 15

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

Question 16

Describe innate / nonspecific immunity

Answer 16

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

Question 17

Innate immunity: describe first line of defense

Answer 17

Are physical barriers

Skin
Mucous membranes
Salina
Tears
Acid in stomach, vagina, urinary tract
Urine flushes through urinary passageways 
Cilia

Question 18

Innate immunity: second line of defense

Answer 18

Involves white blood cells, chemical mediators, inflammation, fever

Question 19

Innate immunity: second line of defense- white blood cells

Answer 19

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

Question 20

Innate immunity: second line of defense- chemical mediators

Answer 20

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

Question 21

Innate immunity: second line of defense- inflammation

Answer 21

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

Question 22

Innate immunity: second line of defense- fever

Answer 22

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

Question 23

Describe adaptive / specific immunity

Answer 23

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

Question 24

Adaptive immunity: cell mediated immunity

Answer 24

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.

Question 25

Adaptive immunity: antibody mediated immunity

Answer 25

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

Question 26

Describe memory responses

Answer 26

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

Question 27

How can adaptive immunity be acquired

Answer 27

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)