Comparative Anatomy of the haematopoietic system + component parts Flashcards
What is the Haematopoietic system?
organs and tissues involved in the production of cellular blood components
What are the components of the blood?
bone marrow
spleen
thymus
lymph nodes
Haematopoiesis?
production of blood cells
What is derived from Haematopoietic stem cells?
erythrocytes (RBC)
Cells of the myeloid lineage (incl. granulocytes, macrophages)
Lymphocytes (T,B,NK cells)
What is the bone marrow the site of?
most blood cell formation in adults
Where is the bone marrow found?
within the medullary cavity and interstitial spaces of spongy bone
What function does Red bone have?
Haematopoietic function
Describe the vascularisation of red bone:
richly vascularised
ALL BM IS RED IN YOUNG ANIMALS
How many types of bone marrow is there?
two
red and yellow
What is yellow bone marrow?
it is predominantly fat
it has dormant Haematopoietic potential
conversion from red to yellow happens in larger spaces first
What are the 2 main components and functions of the lymphatic system?
circulation of interstitial fluid around the body
immunological defence of the body
(both functions are interwined)
What happens at primary lymphatic organs?
where lymphocytes are formed and mature
Give examples of primary lymphatic organs?
red bone marrow
thymus gland
(Bursa of Fabricius in birds)
(Peyer’s patches in many species: rabbits, ruminants, pigs)
What do primary lymphatic organs provide an environment for?
for stem cells to divide and mature into B- and T-cells
Where do B and T cells originate?
in the bone marrow
Where do T cells have to migrate to and why?
to thymus gland in order to fully mature
What are secondary lymphoid tissues?
they are filters which monitor content of extracellular fluids (lymph, tissue fluid, blood)
give examples of secondary lymphoid tissues:
lymph nodes
spleen
mucosa associated lymphoid (MALT)
e.g. Peyer’s patches, tonsils
Where are lymphocytes activated?
in secondary lymphoid tissues
what is filtered out of capillaries?
fluid - interstitial fluid
fluid is forced into interstitial space
how is fluid filtered out of capillaries?
balance between hydrostatic and oncotic pressures
composition of lymph is the same as?
interstitial fluid
Not all fluid is… into capillaries?
reabsorbed
the excess fluid is drained, it passes through lymph vessels, lymphatic system and red bone marrow
there is a balance between opposing pressures
where does the circulating lymph go?
eventually returns to cardiovascular system (back to blood)
Lymph travels through…
progressively larger lymphatic vessels until emptied back into venous circulation
may pass through lymph nodes
thoracic duct commonly drains into left branches of vena cava
(e.g. left jugular v., subclavian v., brachiocephalic)
what shows up black on an x-ray?
air - an air filled organ is the stomach
At what pressure does lymph flow at?
at low pressure
walls of lymph nodes?
thin walled and permeable
describe the lymph vessels?
they readily collapse (hard to see on histological sections)
valves to prevent backflow
elevations in venous pressure can disrupt lymph flow
lymph nodes?
they exist along lymphatic pathways
they survey lymph content for tissue pathogens
germinal centres?
clusters of B lymphocytes waiting to be activated and proliferate
Efferent lymph vessels?
they originate in the central medulla
afferent?
is arriving at the lymph node
efferent?
is exiting
where do efferent vessels originate and leave?
they originate in central medulla and leave lymph nodes from indented hilar regions
how are pigs lymph nodes different?
cortical tissue is central
afferent vessels penetrate capsule near hilus
(at 1 or more sites)
efferent vessels emerge from periphery
what do we look at to determine the safety of meat for human consumption?
remove tongue, trachea and lungs and look at the lymph nodes for signs of disease
haemal nodes? which species?
not found in all species
more common in sheep and cattle
function of haem nodes?
similar function to spleen
they filter blood
they contain blood sinuses
vascular structures modified by focal collections of lymphocytes
where are peyer’s patches found?
mostly in the ileum and jejunum
(lamina propria and submucosa)
how are peyer’s patches distinguishable?
by lack of villi covering them
spleen location?
found in left cranial part of abdomen and is attached to greater curvature of stomach by gastrosplenic ligament
exact position of spleen depends on?
on blood content and stomach filling
morphology of spleen differs between species give e.g. :
*Dumbbell-shape in dog and cat
*Strap-like in pig
*Broad oblong in cattle
*Hooked in horse
what blood vessels supply the spleen?
by splenic a. and v.
*Pass undivided through confined hilus(ruminant)
*Run along organ branching at intervals (horse, pig)
*Divide as approach organ (dog, ca
spleen stored what for emeegencies?
stores blood
important functions of spleen?
*Blood storage
*Blood filter
*Destruction of old RBCs
*Lymphocyte activation
thymus?
control organ of immune and lymphatic systems
function of thymus?
produces huge numbers of T cells
size of thymus?
great size and importance in juvenile
it gradually involutes (smaller) until puberty
regression starts at cervical/cranial end
lymphoid structure replaced by fat
position of thymus?
paired position either side of trachea
it extends caudally to the thorax in the neonate
fused with pericardium
can look like a single median organ in some species
structures that make up the thymus?
connective tissue capsule
dense cortex
medulla
blood-thymus barrier in capillaries
Primary lymphoid organs of birds?
thymus (3-8pale lobes near jugular v.)
Bursa of Fabricius (aka Cloaca bursa)
Secondary lymphoid organs of birds?
bone marrow
spleen
intestinal lymphoid tissue
lymph nodes, birds?
NO
but ducks and geese yes unlikely to feel
Spleen located - birds?
between ventriculus (gizzard) and proventriculus
does not form blood reservoir in as in mammals
quite small
oval/triangulated/elongated
thymus of amphibians function?
produces T cells
remains functional throughout life
malnutrition/chronic stress can lead to involution
some amphibian species have haematopoietic bone marrow and others have?
functionally equivalent centres in spleen and liver
spleen of amphibians?
Red pulp (erythropoiesis)
White pulp (myelopoeisis)
GALT?
amphibians
Gut-associated lymphoid tissue
What are secondary lymphoid tissues?
they are filters which monitor content of extracellular fluids e.g. lymph, tissue fluid, blood
Give examples of secondary lymphoid tissues?
lymph nodes
spleen
mucosa associated lymphoid tissue (MALT)
Give examples of MALT:
(mucosa associated lymphoid tissue)
Peyer’s patches, tonsils
where are the sites of lymphocyte development?
thymus
bursa
Peyer’s patches
Bone marrow
[THESE ARE ALL PRIMARY LYMPHOID ORGANS]
Where are the sites where lymphocytes respond to antigens?
tonsils
spleen
lymph nodes
Peyer’s patches
Bone marrow
[THESE ARE ALL SECONDARY LYMPHOID ORGANS]
What are the sources of lymphocytes?
Yolk sac
Fetal liver
Bone marrow
How are lymphocytes activated in the secondary lymphoid organs?
via antigen-dependent proliferation and differentiation into antigen-disposal cells or memory cells
Give examples of MALT
(mucosal associated lymphoid tissue)
Pharyngeal (tonsils)
Palatine (tonsils)
Larynx
Intestine (Peyer’s patches)
Prepuce
Vagina
What is MALT?
aggregations of unencapsulated lymph nodules in mucosae
How does MALT differ from lymph nodes?
absence of capsule
close relationship to epithelial surface
positioned at origin of lymphatic drainage pathway
where are Peyer’s patches mostly found?
on the ileum and jejunum in the lamina propria and submucosa
what is the morphology of the spleen like between different species?
in dog, cat, pig, cattle and horse
Dumbbell - shape in dog and cat
strap - like shape in pig
broad oblong in cattle
hooked in horse
What supplies the spleen with blood?
the splenic a. and v.
describe the splenic a. and v. in ruminants:
it passes undivided through confined hilus
describe the splenic a. and v. in horses and pigs:
it runs along the organ branching at intervals
describe the splenic a. and v. in dogs and cats:
it divides as it approaches the organ
What are the important functions of the spleen - these are important but not vital:
Blood storage
Blood filter
Destructions of old RBCs
Lymphocyte activation
what does the parenchyma divide into?
into red and white pulp
what is the red pulp of the parenchyma?
it is venous sinuses
what is the white pulp of the parenchyma?
lymph nodules
where does the capsule of the spleen extend into?
it extends trabeculae into interior of the spleen
what is parenchyma?
it is a simple permanent tissue
What is the thymus?
it is a control organ of the immune and lymphatic systems
what does the thymus produce?
it produces lots of T cells
Thymus in a juvenile?
it is of great size and importance
Describe the ‘journey’ of the thymus from when it is first present in a juvenile:
it gradually involutes until puberty
regression starts at cervical/cranial end
lymphoid structure replaced by fat
Describe the location of the thymus?
it has a paired position either side of the trachea and it extends caudally to the thorax in the neonate
fused with PERICARDIUM
can look like a single median organ in some species (as we saw in that cat anatomy prac)
Describe the structure of the thymus?
it is a connective tissue capsule
trabeculae enter and divide organ into lobules
houses blood vessel, nerves and efferent lymphatics
describe the cortex of the thymus?
it has a dense cortex
rapidly dividing thymocytes
what are rapidly dividing thymocytes?
developing T cells
describe the medulla of the thymus?
it contains non-dividing more mature T cells
if there are fewer T cells in the medulla of the thymus - how can we tell?
there is weaker staining
what is the point of the blood-thymus barrier in capillaries?
it protects T cells from exposure to antigens in blood
Describe the Bursa of Fabricius in birds?
the dorsal diverticulum is in the proctodeum
contains folds of lymphoid tissue
thick wall in domestic fowl, thin and saclike in psittacine and passerines
what is the proctodeum?
it is the most caudal portion of the cloaca (Bursa of Fabricius) - it serves as a reservoir for waste and urine before excretion
when does the Bursa Fabricius of birds reach maximum size?
reaches maximum size before sexual maturity and then begins to involute (get smaller)
In birds, where is the spleen located?
between ventriculus (‘gizzard’) and proventriculus
what is the ventriculus? BIRD
it is the muscular stomach - used for grinding food
what is the proventriculus? BIRD
it is normally found between the ventriculus and oesophagus - it is a rod shaped organ that is glandular and it stores food before the food progresses to the ventriculus
what does the spleen not form in mammals?
it does not form a blood reservoir in mammals
describe the size of the spleen in birds:
it is quite small
describe the shape of the spleen in birds:
it is oval or triangular or elongated
describe the lymphatic vessels of the birds in the spleen:
they have fewer numbers of lymphatic vessels than mammals
they usually follow the blood vessels closely
they have valves (like mammals)
what is the point of the thoracic ducts in birds?
they drain the lymph from the hindlimb and abdominal vessels and they deliver it into the jugular veins at the base of the neck
where are the thoracic ducts normally found in most bird species?
most species have paired thoracic ducts either side of spine
what do amphibians lack?
they lack lymph nodes
what does the lymphatic system of amphibians include?
includes lymph hearts
what are lymph hearts (found in amphibians) also known as?
lymph sacs or vesicles
what are lymph hearts?
they are smooth muscle dilations of lymphatic channels
they beat independently of the heart
ensure unidirectional lymph flow to heart
what is the heart rate of the lymph hearts found in amphibians?
50-60bpm
Describe the thymus gland of reptiles?
1-2 yellow/white lobes
each side of the neck in lizards/chelonia
doesn’t involute, but weight & size decreases w/ age
where are the paired thymus glands located in snakes?
just cranial to the heart
do reptiles have bone marrow and a spleen?
yes
what do reptiles lack?
lymph nodes
what do reptiles have instead of lymph nodes?
vast plexiform lymphatic networks and large dilated reservoirs (cisternae)
other than amphibians, who else have lymph hearts?
reptiles
describe the lymphatic trunks of reptiles:
well-developed lymphatic trunks
give examples of the well-developed lymphatic trunks of reptiles:
the jugular, subclavian, lumbar and thoracic
what passes lymph to the venous system in reptiles?
a saccular precardiac sinus at the base of the neck
what is the lymphatic system intimately associated with - reptiles?
with the blood
what is a common contaminant of blood samples in reptiles?
Lymphdilution is a common contaminant e.g. low PCV
so you have to be careful how you sample blood in reptiles
where can you take blood samples from in a red-footed tortoise?
Dorsal coccygeal (tail) vein
ALSO
jugular vein blood sampling
