deck_16403300 Flashcards
what is lymphatic system
..
consists of
Lymphatic vessels
liquid CT called lymph
Lymphatic organs and tissues
(immune response)
what systems are closely integrated with lymphatic system
cardiovascular and gastrointestinal systems
major functions of lymphatic system
1) Draining excess interstitial fluid (vessels)
2) Carries out immune responses (organs/nodes/tissues)
3) Transporting dietary lipids absorbed by the gastrointestinal tract to the blood (lacteals/vessels)
1) Draining excess interstitial fluid (vessels)
HOW MUCH (litres)
what other component does lymphatic system return to blood?
Approximately 3.5 L per day
Returns lost PLASMA PROTEINS to bloodstream
2) Carries out immune responses (organs/nodes/tissues)
which immune response type?
Adaptive immune response (lymphocytes)
3) Transporting dietary lipids absorbed by the gastrointestinal tract to the blood (lacteals/vessels)
INCLUDING WHICH VITAMINS
Fat soluble vitamins (A, D, E & K)
ADEK
components of lymphatic system
1) Lymph
2) Lymphatic vessels
3) Lymphatic tissues
4) Lymphocytes
what does lymph resemble
closely resembles interstitial fluid
lymph vs isf
Lymphatic fluid contains lymphocytes, while interstitial fluid contains phagocytes (both are types of white blood cells).
lymph/isf vs plasma
Both lymph and interstitial fluid have relatively less protein than plasma. This is because the lymph mainly consists of leaked interstitial fluid. This leak consists of water, cells, smaller proteins but the larger proteins do not leak through.
isf vs plasma
Plasma has a much higher protein concentration than interstitial fluid due to the presence of albumin, globulins, and fibrinogen.
Additionally, plasma oxygen levels are significantly higher than those of interstitial fluid, which is largely due to the presence of red blood cells carrying oxygen in the plasma.
lymphatic vessels consist of
capillaries, vessels, trunks, ducts
two types of lymphatic tissues
Primary and secondary lymphatic tissues
lymphocytes are
Cells of the lymphatic system (T-cells and B-cells)
1) lymphatic fluid (lymph)
Liquid connective tissue
Formed when excess interstitial fluid enters lymphatic capillaries
Usually clear (exception is in GIT when it appears milky due to absorbed dietary lipids, “lacteal”)
what does lymph contain
Contains immune cells
“Lymphatic fluid contains lymphocytes” (?)
2) LYMPHATIC VESSELS ****
Often called lymphatics
Carry lymph from peripheral tissues to venous system
Found in close association
with blood vessels
Network begins with lymphatic capillaries (smallest vessels)
lymph vessels: capillaries
Differ from blood capillaries:
i) Closed at one end (blind-ended)
ii) Have larger diameters
iii) Have thinner walls —> Basement membrane is incomplete or absent
iv) Typically have a flattened or irregular outline in sectional view
lymph vessels – what is unique about endothelial cells
Have overlapping endothelial cells:
i) Region of overlap acts as a one-way valve
ii) Permits entry of fluid and solutes (including proteins)
—-> Also allows entry of viruses, bacteria, cell debris
—-> Prevents return of these materials to the intercellular space
note “one-way flow” of lymphatic vessel wall
(via endothelial cell alignment/structure)
“Prevents return of these materials to the intercellular space”
“Pressure changes between the interstitial fluid and lymph cause opening or closing of the endothelial “doors””
I.e.
—> materials can go in, but not back out (?)
note “anchoring filament” of endothelial cells of lymph vessels
anchor vessels to surround ISF/cells structures
Lacteals
“the lymphatic vessels of the small intestine which absorb digested fats.”
Specialized lymphatic capillaries Located in small intestine
Carry dietary lipids into lymphatic vessels
Chyle
Lymph in lacteals appears creamy white because of fat; referred to as CHYLE
Chyle:
“a milky fluid consisting of fat droplets and lymph. It drains from the lacteals of the small intestine into the lymphatic system during digestion.”
where does lymph go from the lymphatic capillaries
Lymph from capillaries flow into larger lymphatic vessels that lead toward the body’s trunk
VALVES of lymphatic vessels
Vessel bulges at each valve
—> “Series of bulges makes vessel resemble string of pearls”
what feature of lymphatic vessels necessitates presence of valves
Low pressure in lymphatic vessels
—> Valves prevent backflow of lymph
what other feature helps movement of lymph in the vessels
Contraction of surrounding skeletal muscles aids flow of lymph
superficial vs deep lymphatics
..
superficial lymphatics – where?
i) Subcutaneous layer deep to skin
ii) Areolar tissues of mucous membranes
(digestive, respiratory, urinary, and reproductive tracts)
iii) Areolar tissues of serous membranes
(pleural, pericardial, and peritoneal cavities)
deep lymphatics – where?
Accompany deep arteries and veins supplying skeletal muscles and other organs of the neck, limbs, and trunk, and wall of visceral organs
which direction is lymphatic flow ?
Always from periphery to central vasculature
steps in lymphatic flow
- Begins as interstitial fluid
- Enters lymphatic capillaries (forms lymph)
- Travels in lymphatic vessels to regional lymph nodes
- Enters lymphatic trunks
- Drains into either left or right lymphatic ducts
- Ducts return lymph to blood stream at subclavian veins
capillaries –> vessels (?) –> trunks –> ducts
?
about lymphatic trunks
Formed by confluence of many efferent lymph vessels
node meaning of efferent vs afferent in the context of lymphatic vessels
Afferent (toward) lymphatic vessels convey unfiltered lymphatic fluid from the body tissues to the lymph nodes,
and efferent (away) lymphatic vessels convey filtered lymphatic fluid from lymph nodes to subsequent lymph nodes or into the venous system.
named lymphatic trunks
R/L Lumbar trunks
R/L Intestinal trunks
R/L bronchomediastinal trunks
R/L subclavian trunks
R/L jugular trunks
R/L Lumbar trunks
Drain the lower limbs, the wall and viscera of the pelvis, kidneys, adrenal glands and abdominal wall
R/L Intestinal trunks
Drain the stomach, intestines, pancreas, spleen, part of the liver
R/L bronchomediastinal trunks
Drain the thoracic wall, lung, heart
R/L subclavian trunks
Drain upper limbs
R/L jugular trunks
Drain head and neck
WHERE DO TRUNKS DRAIN INTO?
they drain into
A) THE THORACIC DUCT (Aka Left Lymphatic Duct)
B) RIGHT LYMPHATIC DUCT
which duct drains from most of the body?
THORACIC DUCT (LEFT LYMPHATIC DUCT)
1) Thoracic Duct
(Aka left lymphatic duct)
Collects lymph from:
—> Entire body inferior to the diaphragm
—> The left side of the body superior to the diaphragm
where does thoracic duct drain?
Drains into the left subclavian vein
2) Right Lymphatic Duct
Collects lymph from:
—> The right side of the body superior to the diaphragm
where does right lymphatic duct drain?
Drains into the right subclavian vein
where does Thoracic (left lymphatic) duct begin?
Begins as a dilation called cisterna chyli
@ LEVEL OF L2
(anterior to “)
which trunks does thoracic duct receive lymph from?
Right and left lumbar trunks
Right and left intestinal trunks
Left bronchomediastinal trunk
Left subclavian trunk
Left jugular trunk
where exactly does thoracic duct drain lymph into?
Drains lymph into venous blood
—> at the junction of the left INTERNAL JUGULAR and left SUBCLAVIAN veins
where does right lymphatic duct receive lymph from?
Right bronchiomediastinal trunk
Right subclavian trunk
Right jugular trunk
where does right lymphatic duct drain lymph into
Drains lymph into venous blood
—> at the junction of the right internal jugular and right subclavian veins
recap of lymphatic flow
Blood capillaries interstitial space lymphatic capillaries lymphatic vessels lymphatic trunks lymphatic ducts subclavian veins
= —>
recall – mechanisms of lymph movement
recall lymph vessels themselves don’t have much pressure
(no/ very little smooth muscle)
1) Pressure in the interstitial space
2) ‘Milking’ action of skeletal muscle contractions
3) Pressure changes during inhalation and exhalation (respiratory pump)
recall respiratory pump
“The respiratory pump is a mechanism to pump blood back to the heart using inspiration. It aids blood flow through the veins of the thorax and abdomen.”
“During inhalation, the volume of the thorax increases, largely through the contraction of the diaphragm, which moves downward and compresses the abdominal cavity.”
what happens if lymph flow does not occur?
Obstruction or malfunction of lymph flow => lymphedema
lymphedema
Caused by blocked lymphatic drainage:
—> Interstitial fluids accumulate
—> Affected area becomes swollen and distended
where is lymphedema most often seen?
Most often seen in limbs but can
affect other areas
what permanent changes can take place in the CT with excessive / long-term lymphedema?
Swelling may become permanent
—> Connective tissue loses elasticity
what other immune-related issues can take place with stagnant ISF that is not being filtered properly??
Stagnant interstitial fluids may
accumulate toxins and pathogens
—> Local immune defenses
overwhelmed
3) LYMPHOID TISSUES ****
..
lymphoid tissues can either be …
A) Lymphoid nodules
B) Lymphoid organs
a) lymphoid nodules
Densely packed lymphocytes in an area of areolar tissue
Nodules may cluster together and form larger masses
No fibrous capsule surrounds the masses
lymphoid nodules vs nodes
Lymph nodules form in regions of frequent exposure to microorganisms or foreign materials and contribute to the defense against them.
The nodule differs from a lymph node in that it is much smaller and does not have a well-defined connective-tissue capsule as a boundary.
b) lymphoid organs
Separated from surrounding tissues by fibrous connective tissue capsule
another way of classifying lymphoid tissues
primary vs secondary lymphatic tissues
two ways of classifying?
nodules vs organs
primary vs secondary
(?)
primary lymphatic tissues =
Red bone marrow and thymus
—> Sites where lymphocytes are made and/or become immunocompetent (mature)
secondary lymphatic tissues =
Lymph nodes, spleen, lymphatic nodules
—> Where lymphocytes are activated and cloned
—> Site of most immune responses
SO LYMPHOID NODULES (vs organs) are always (?)
Secondary lymphatic tissues
(?)
about red bone marrow
(Primary lymphatic tissue)
and lymphatic organ
= PRIMARY LYMPHOID ORGAN
Pluripotent stem cells in red bone marrow give rise to:
—> Mature immunocompetent B cells
—> Pre-T cells
(Migrate to the thymus where they become immunocompetent T cells)
about thymus
(primary lymphatic tissue,
and lymphoid organ)
= PRIMARY LYMPHOID ORGAN
..
thymus size/function
The thymus is a lymphoid organ that produces functional T cells
Produces several hormones (thymosins) important in functional T cell development
what happens to thymus with age?
Size and secretory abilities decline with age:
—> Size is largest (40 g) before puberty
—> Diminishes in size and becomes increasingly fibrous (involution)
—> By age 50, size can be <12 g
—> Correlated with increased susceptibility to disease
Thymus description
Located in the mediastinum
—> Posterior to the sternum
(anterior mediastinum)
—> Covered in a capsule that divides it into left and right lobes
Fibrous partitions (septa) divide the lobes into lobules
—-> Each lobule is about 2 mm in diameter
thymus histology
Each lobule consists of:
i) Dark outer cortex
ii) Lighter central medulla
i) Dark outer cortex
Contains dividing lymphocytes arranged in clusters surrounded by epithelial reticular cells (ERCs)
—> Regulate T cell development and function
Blood vessels in the cortex are also surrounded by epithelial cells
—> Maintain the BLOOD THYMUS BARRIER
epithelial reticular cells
“Besides the role of providing a structural support for lymphocytes, epithelial reticular cells are responsible for the secretion of thymic hormones which promote lymphocyte proliferation and maturation.”
blood thymus barrier
“The main purpose of the blood thymus barrier is to prevent cortical T lymphocytes from interacting with foreign macromolecules.”
what are the cells of the DARK OUTER CORTEX
(of lobules of thymus)
Pre-T cells from red bone marrow
Dendritic cells
—> Assist T cell maturation
Epithelial cells
—> Help educate pre-T cells in a process known as positive selection, produce thymic hormones thought to aid in T cell maturation
Macrophages
—> Help to clear out the debris of dead and dying cells
recall dendritic cells
“A dendritic cell is a type of phagocyte and a type of antigen-presenting cell (APC).”
“A special type of immune cell that is found in tissues, such as the skin, and boosts immune responses by showing antigens on its surface to other cells of the immune system.”
what percentage of developing T cells survive?
Only about 2% of the developing T cells survive – the remaining cells die via apoptosis
where do the surviving T cells go?
The surviving T cells then enter the inner medulla
how long does it take survivng T cells to go to inner medulla of lobules?
Developing T cells leave the cortex after about 3 weeks and enter the medulla
NOTE***
No blood thymus barrier in medulla
what are the cells inside the inner medulla?
Mature T cells
Dendritic cells
Epithelial cells
—> Create clusters called thymic (Hassall’s) corpuscles
—> Role unknown – may serve as a site of T cell death in the medulla
Macrophages
So what is the major difference between cells of dark outer cortex and light inner medulla of the LOBULES of the thymus?
maturity of T cells
outer cortex = pre-T cells
inner medula = mature “
where do T cells go after leaving the thymus?
T cells that leave the thymus via the blood travel to
lymph nodes, spleen and other lymphatic tissue.
Thymic (Hassall’s) Corpuscles
“one of the small usually concentrically striated bodies in the thymus body representing remains of the epithelial tissue found in early stages of development.”
“Hassall’s corpuscles (also known as thymic bodies) are structures found in the medulla of the human thymus, formed from eosinophilic type VI thymic epithelial cells arranged concentrically.”
LYMPH NODES
SECONDARY (tissue)
Lymphoid organ
Small lymphoid organs surrounded by fibrous connective tissue capsule
Shape resembles a kidney bean
Diameter range 1–25 mm (about 1 in.)
large lymph nodes – aka
Large lymph nodes (lymph glands) located in neck, groin, axillae
what is function of lymph nodes
Function as filters, removing 99 percent of pathogens from lymph before fluid returns to bloodstream
superficial vs deep
Superficial and deep lymph nodes
important lymph nodes (HEAD AND NECK)
Submental and submandibular lymph nodes
Anterior and posterior cervical lymph nodes
Supraclavicular lymph nodes
important lymph nodes (ARMS)
Axillary lymph nodes
important lymph nodes (LEGS)
Inguinal lymph nodes
Femoral lymph nodes
lymph node structure
Covered by a capsule of dense CT
Capsular extensions (EXTENDING INWAR) called trabeculae
—> Divide the node into compartments
—> Provide support
—> Provide a route for blood vessels
Stroma of lymph node
Composed of the capsule, trabeculae, reticular fibers (inside node) and fibroblasts
parenchyma vs stroma
a parenchyma is a structure involved directly in the function of a given organ or organelle.
Stroma, on the other hand, is tissue acting as structural support for these parenchyma.
Parenchyma of lymph node
i) Cortex
ii) Medulla
Cortex of lymph node (parenchyma)
Outer cortex
—> Consists mostly of B cells
Inner cortex
—> Consists mainly of T cells and dendritic cells that enter a lymph node from other tissue
Medulla of lymph node (parenchyma)
Contains B cells, plasma cells and macrophages
lymph nodes general function
Type of filter:
Foreign substances are trapped by the reticular fibers within the sinuses
—> Macrophages destroy by phagocytosis
—> Lymphocytes create immune responses
Path of lymph through a lymph node
(afferent vessels/lymphatics)
Afferent (afferens, to bring to) lymphatics bring lymph into the node on the opposite side
from the hilum (indentation)
hilum
“another term for hilus.”
“an indentation in the surface of a kidney, spleen, or other organ, where blood vessels, ducts, nerve fibers, etc. enter or leave it.”
Path of lymph through a lymph node —> all the steps
- Afferent (afferens, to bring to) lymphatics bring lymph into the node on the opposite side
from the hilum (indentation) - Through the subcapsular space
—> Network of fibers and dendritic cells (involved in immune response) - Into the outer cortex
—> Contains B cells within germinal centers - Through lymph sinuses in the paracortex
—> Contains T cells - Into the medullary sinus at the core
—> Contains B cells and plasma cells - Out of the lymph node in efferent (efferens, to bring out) lymphatics at the hilum and into venous circulation
path of lymph through lymph node – RECAP
afferent lymphatics
—> Subcapsular space
—> Outer cortex
—> Paracortex
—> Medullary Sinus
—> efferent lymphatics (via hilum)
Spleen
lecondary lymphatic tissue
lymphoid organ
Contains the largest mass of lymphoid tissue in the body
spleen function
Performs same function for blood that lymph nodes do for lymph (filter)
spleen function..
Removes abnormal red blood cells and other blood components by phagocytosis
Stores iron recycled from red blood cells
Initiates immune response by B cells and T cells in response to antigens in circulating blood
liver vs spleen RBC breakdown (???)
““The liver, not the spleen, is the major on-demand site of red blood cell elimination and iron recycling,” according to Filip Swirski, PhD, of the Massachusetts General Hospital Center for Systems Biology, and his colleagues.”
spleen diaphragmatic surface
Smooth and convex
Conforms to the shape of the diaphragm and the body wall
spleen gross anatomy
Lies along the curving lateral border of the stomach on the left side
Attached to lateral border of the stomach by the gastrosplenic ligament (broad band of mesentery)
other gross anatomy facts about spleen
About 12 cm (5 in.) long and weighs ~160 g (5.6 oz.)
Deep red when dissected
(Due to large amounts of blood it contains)
Soft texture
–> Shape molded by structures around it
Visceral (medial) surface has two indentations:
—> Gastric area (near stomach)
—> Renal area (near kidney)
Hilum (indentation where blood and lymphatic vessels communicate)
spleen structure
Outer capsule of collagen and elastic fibers
—> Fairly easily ruptured by impact
—> Spleen tissue too fragile to repair surgically
—> Damage can necessitate removal (splenectomy)
Trabeculae
Fibrous partitions that radiate (INWARD) from the capsule
(similar to nodes)
parenchyma of spleen
Parenchyma is made up of pulp:
Cellular components within the capsule
two types of pulp within spleen (within capsule)
RED pulp
WHITE pulp
Red pulp
Consists of blood filled venous sinuses and cords of splenic tissue called splenic (Billroth’s) cords
—> Consist of many red blood cells and macrophages
Billroth’s cords
“WThe cords of Billroth (also known as splenic cords or red pulp cords) are found in the red pulp of the spleen between the sinusoids, consisting of fibrils and connective tissue cells with a large population of monocytes and macrophages.”
White pulp
Lymphatic tissue: mostly lymphocytes and macrophages
Arranged around branches of the splenic artery called central arteries
function of red pulp
- Removal by macrophages of ruptured, worn out or defective blood cells and platelets
- Storage of platelets (up to 1/3rd of body’s supply)
3.Production of blood cells (hematopoiesis) during fetal life
function of white pulp
Splenic arteries carry blood to central arteries of white pulp
—> B cells and T cells carry out immune functions in white pulp
—> Spleen acts like an ‘immune filter’ of the blood
ruptured spleen
Spleen tears easily and is difficult to repair surgically
Treatment is a splenectomy: removal of spleen
—> Without a spleen, person has increased risk for bacterial infection
—> Liver and bone marrow can take over some functions
Lymphoid nodules
(secondary tissue)
Lymphoid nodules are egg-shaped masses of lymphatic tissue
Differ from lymph nodes because they are NOT surrounded by a capsule (NODULES, not organs)
where are lymphoid nodules
Scattered throughout the lamina propria (CT) of mucous membranes lining the gastrointestinal, urinary and reproductive tracts and respiratory airways
why? (lymphoid nodules)
“Lymph nodules form in regions of frequent exposure to microorganisms or foreign materials and contribute to the defense against them.”
(Lymphoid nodule locations)
Mucosa-associated lymphoid tissue (MALT)
Mucosa-associated lymphoid tissue (MALT)
—> Protect epithelia of digestive, respiratory, urinary, and reproductive tracts from pathogens and toxins
Examples of MALT
E.g.
—> GALT (gut-associated lymphoid tissue)
—> Peyer’s Patches (small intestine)
—> Tonsils
note tonsils
Large lymphoid nodules in the walls of the pharynx
—> Pharyngeal tonsil (or the adenoid)
Located on posterior superior wall of the nasopharynx
—> Palatine tonsils (left and right)
Located at posterior, inferior margin of the oral cavity along the boundary of the pharynx
—> Lingual tonsils
Pair of tonsils located deep to the epithelium covering the base of the tongue
Tonsillitis
inflammation of tonsils
clinical disorders (related to lymphatic nodules)
MALT defends exposed epithelia in multiple tracts exposed to the exterior environment
Infection and/or inflammation of MALT components can cause variety of clinical disorders
*
E.g.
—> Tonsillitis (inflammation of the tonsils)
—> Appendicitis (inflammation of the lymphoid tissue in the appendix)
lecture 2
..
immunity
The ability to fight infection, illness, and disease
two mechanisms – work independently and together
1. Innate (nonspecific) immunity
- Adaptive (specific) immunity
Innate (nonspecific) immunity
Present at birth (innate)
Does not distinguish one type of threat from another (non-specific)
Response is the same regardless of type of invading agent
Prevents the approach, denies the entry, limits the spread of microbes or other environmental hazards
Adaptive (specific) immunity (Acquired immunity)
Utilizes adaptive defenses
Develops over time (acquired)
Protects against particular threats (specific)
Depends on the activities of specific lymphocytes
1st line defense (part of innate IS)
skin
mucous membranes
secretions of skin and MM
2nd line defense
phagocytes
antimicrobial proteins (other than complement & IFNs)
inflammation
fever
3rd line defense
lymphocytes
antibodies
memory cells
cells of innate (MONONUCLEAR PHAGOCYTES)
macrophage (APC)
&monocyte
dendritic cells (APC)
macrophage vs monocyte (recall)
Macrophages are monocytes that have migrated from the bloodstream into any tissue in the body.
cells of innate IS (granulocytes)
basophils
eosinophils
neutrophils
cells of innate IS (lymphocyte?)
NK cells
innate IS other
mast cells?
complement protein system
innate IS
macrophage (APC)
&monocyte
dendritic cells (APC)
basophils
eosinophils
neutrophils
mast cells?
NK cells
complement protein system
component of innate IS
Physical barriers and chemical barriers
Phagocytes
Immune surveillance
Interferons
Complement
Inflammation
Fever
Physical barriers and chemical barriers
skin and mucous membranes
Phagocytes
cells that engulf pathogens and cell debris
Immune surveillance
destruction of abnormal cells by natural killer (NK) cells
Interferons
chemicals against viral infections
Complement
circulating proteins that assist antibodies
Inflammation
localized tissue-level response to limit spread of infection
Fever
elevation of body temperature
interferons??? PROTEINS
A natural substance that helps the body’s immune system fight infection and other diseases, such as cancer.
Interferons are made in the body by white blood cells and other cells
“Interferons are a group of signaling proteins made and released by host cells in response to the presence of several viruses.”
interferon types
There are three types of interferons (IFN), alpha, beta and gamma.
IFN-alpha is produced in the leukocytes infected with virus,
while IFN-beta is from fibroblasts infected with virus.
IFN-gamma is induced by the stimulation of sensitized lymphocytes with antigen
or non-sensitized lymphocytes with mitogens.
mitogen
a substance that induces or stimulates mitosis.
1st line of defense (PHYSICAL)… 1)
1) Integumentary system:
Stratified squamous epithelium
Secretions
Hair
