HISTOLOGY Flashcards
what bone marrow cells produce platelets?
megakaryocytes
what bones retain hemopoiesis?
vertebrae ribs skull pelvis proximal femur
what is the main site of hemopoiesis after birth?
bone marrow
what are the three layers of a blood vessel? (from inner to outer)
tunica intima (inner) tunica media (middle) tunica adventitia (outer)
describe the tunica intima (3)
inner layer of a blood vessel
a single layer of squamous epithelail cells (endothelium)
supported by a basal lamina and a thin layer of connective tissue
describe the tunica media (3)
middle layer
predominantly smooth muscle, some elastic fibres
thickness of this layer varies
describe the tunica adventitia (2)
outer layer
made up of supportive connective tissue
what separates the tunica intima and the tunica media?
a layer of elastic tissue called the internal elastic membrane
what separates the tunica media from the tunica adventitia?
a layer of elastic tissue called the external elastic membrane
what is an elastic artery?
an artery in which a significant amount of the smooth muscle in the tunica media is replaced by sheets of elastic fibres
what do sheets of elastic fibres in the tunica media allow?
elastic recoil
why do large arteries have their own vascular supply and what is this called?
only the inner part of the wall can obtain nutrients from the lumen
the vasa vasorum
how are arterioles formed?
arteries become smaller and lose smooth muscle from their tunica media
what are arterioles important for?
controlling blood flow in a tissue
describe the structure of capillaries (3)
composed of endothelial cells and a basal lamina
diameter of between 4 and 8 micrometers
they form networks
what are the three types of capillaries?
continuous
fenestrated
discontinuous/sinusoidal
where are continuous capillaries found? (4)
muscle, nerves, lungs and skin
describe fenestrated capillaries
have small pores
found in the gut mucsosa, endocrine glands and the kidneys
describe discontinuous capillaries
have large gaps
found in the liver, spleen and bone marrow
describe venules (4)
10 - 30 micrometres in diameter
lined with endothelial cells, contain a thin layer of connective tissue
important sites for exchange
has intwrmittent smooth muscle cells in the tunica media
describe the structure of a vein
tunica intima
tunica adventitia
thin but continuous tunica media, few layers of smooth muscle
describe the structure of the largest veins
thick tunica adventitia which incorporates bundles of longitudinally oriented smooth muscle
why do many veins have valves?
to prevent backflow of blood
what is the lymph vascular system?
a system of relatively thin walled vessels that drain excess tissue fluid called lymph into the blood stream and to lymoh nodes for immunological surveillance
how is flow maintained in the lymph vascular system?
smooth muscle in walls
hydrostatic pressure in tissue
compression of the vessels by voluntary muscle
valves
what is the second site of hemopoiesis?
liver and spleen (mainly the liver) as they are colonized with hemopoietic stem cells
where is the earliest site of hemopoiesis?
in the yolk sac at about 3 weeks of development
what is hemopoiesis?
the production of blood cells
platelets
small cell fragments
play a key role in preventing blood loss
no nucleus
granulated - granules contain coagulation factors
what two main components make up blood?
formed elements
plasma
lymphocytes
round nucleus
thin cytoplasm with no granules
arise in bone marrow
participate in the specific immune response
monocytes (6)
precursors to tissue macrophages predominent in loose connective tissye lysosomal granules in the cytoplasm largest blood cells non lobulated nucleus - kidney bean shaped some are resident to tissues
describe basophils
granules in cytoplasm (affinity for basic dyes)
bilobed nucleus
granules contain inflammatory mediators
degranulation leads to allergic reaction
what is the rarest granulocyte?
basophils
describe eosinophils
granulocytes
granules stained red by eosin
in cicrculation for 8-12 hours then live in tissues
larger than a neutrophil
bilobed nucleus
induce and maintain an inflammatpry response
describe a neutrophil (4)
contain granules in its cytoplasm
multi lobed nucleus
once activated, act as highly motile phagocytes
abundant and short lived, significant proportion of the bone marrow is dedicated to their production
what is the most common type of leukocyte?
neutrophil
what is a leukocyte?
white blood cell
how long do red cells last in circulation and how are they removed?
four months
removed by the spleen and the liver
why do red cells have a network of flexible cytoskeletal elements?
to allow them to deform and slip through spaces smaller than themselves
describe a red blood cell
biconcave disc
7 micrometers in diameter
not a true cell as they contain no nucelus or organelles
contain the protein haemoglobin
what are erythrocytes?
red blood cells
what is it called if clotting factors are removed from blood?
serum
describe the separation of blood in a centrifuge
red cells are the densest and are found at the bottom of the tube
white cells are on top of red cells
plasma is found on top
what are the two types of agranulocytes?
lymphocytes
monocytes
what are the three types of granulocytes?
neutrophils
eosinophils
basophils
what are the two types of white cells?
granulocytes
agranulocytes
what makes up the formed elements of blood?
red cells
white cells
platelets
what do all eukaryotic contain?
an outer membrane cytoplasm cytoskeleton membrane bound organelels inclusions
what is the function of the cytoskeleton?
gives cell shape and fluidity, provides support and structure
what is another name for the cell membrane?
the plasmalemma
what is the cell membrane made up of?
amphipathic phospholipids
describe the phosphilipid head
hydrophillic, faces outer and inner surfaces
describe the phospholipid tail
hydrophobic fatty acid chain
faces the middle of the two layers
what does the cell membrane contain?
integral proteins: receptors, channels, transporters, enzymes and cell attachment proteins
peripheral proteins
cholesterol
what ways can proteins be embedded in the cell membrane?
some can diffuse laterally in the membrane
some are anchored
what is endocytosis?
moving things into the cell
what is exocytosis?
moving things out of the cell
what does the cell membrane provide?
a barrier between the cell and the outside world
what is an organelle?
a small intracellular organ that is essential for life
what is an inclusion?
anything else in a cell that isnt essential for life
how can inclusions get into cells?
synthesised by the cell
taken up from the extracellular environment
what three types of protein filaments make up the cytoskeleton?
microfilaments
intermediate filaments
microfilaments
made from actin
intermediate filaments
made from six types of proteins, varied in different cell types
microtubules
two tubulin protein subunits
how do the filaments of the cytoskeleton attach to the membrane and each other?
by joining proteins to form a 3D internal scaffold inside the cell
why are microfilaments a fluid part of the cytoskeleton?
actin molecules assemble into the filaments and can later dissociate
what type of protein is actin?
globular
