the blood Flashcards
(63 cards)
PLASMA (approx. 55% of blood)
main constituent = water (90-92%), carrying a range of dissolved and suspended substances such as:
-plasma proteins
-nutrients (principally from digested food)
-inorganic salts (electrolytes)
-waste products
-hormones
-gases
PLASMA PROTEINS
-approx. 7% of plasma
-mostly albumin and fibrinogen
-retained within blood due to large size (unable to leave through capillary pores into tissues)
importance of plasma proteins
-responsible for creating osmotic pressure of blood
-this keeps the plasma fluid within circulation
-if plasma protein levels fall, fluid will shift into tissues and body cavities
where are plasma proteins formed ?
the liver (with the exception of immunoglobins)
albumins
-most abundant plasma protein (~60%)
-main function: maintain normal plasma osmotic pressure
-act as carrier molecules for free fatty acids, some drugs and steroid hormones
globulins
main function:
-as antibodies (immunoglobins), are complex proteins produced by lymphocytes and play an important role in immunity
-transport of some hormones and mineral salts
-inhibition of some proteolytic enzymes
clotting factors
-most abundant clotting factor is fibrinogen
-responsible for coagulation of blood
-(serum is plasma where clotting factors are removed)
NUTRIENTS
-essential for cellular growth and metabolism
-e.g. glucose, amino acids + vitamins
-are transported in the bloodstream from site of production/absorption to the tissues to be stored or used immediately
WASTE PRODUCTS
-e.g. urea, creatinine + uric acid
-formed in the liver
-carried in blood to kidneys for excretion
-CO2 from tissue metabolism transported to lungs for excretion
ELECTROLYTES
large range of functions:
-muscle contraction (Ca2+)
-transmission of nerve impulses (Ca2+, K+, Na+)
-maintenance of acid-base balance (phosphate PO4^3-)
HORMONES
-chemical messengers
-synthesised by endocrine glands
-secreted into blood then transported to their target tissues and organs
GASES
-O2 not very soluble in water, only <2% can be transported dissolved in plasma
-O2 bound to haemoglobin (Hb) in RBCs as oxyhaemoglobin (>98%)
-Hb also binds CO2 but most CO2 is converted into bicarbonate ions in RBCs, then transported in plasma
THREE typess of blood cell
-erythrocytes (red cells)
-leukocytes (white cells)
-platelets (thrombocytes)
where are most blood cells synthesised ?
in red bone marrow (some lymphocytes produced in lymphoid tissue)
pluripotency
the ability to develop into one of a number of cell types
what is a feature of all blood cells formed in the bone marrow ?
they all originate from pluripotent stem cells
what is the name of the process of blood cell formation ?
haemopoiesis
how does bone marrow change with age ?
-first few years of life: red marrow completely fills the space within the bone
-next 20 years of life: largely replaced by fatty yellow marrow w/ no haemopoietic function
where does haemopoiesis occur in adults ?
in the skeleton it is confined to:
-flat bones
-irregular bones
-ends of long bones
main sites:
-pelvis (but also sternum + skull)
ERTHROCYTES (red blood cells)
-most abundant type of blood cell (99% of all blood cells)
-biconcave discs w/ NO nucleus
-diameter: approx. 7 µm
main function of erythrocytes
transport of gas (mainly O2, but some CO2)
importance of RBCs shape/structure
-biconcavity increases their SA for gas exchange
-thin central (dip) portion allows gases to enter and exit rapidly
-are flexible so can squeeze through narrow capillaries
-contain NO intracellular organelles to allow for maximal Hb content
-flat shape enables stacking within bloodstream to reduce turbulence
lifespan of erythrocytes
-approx. 120 days in circulation
-approx. 25% of body’s total cell count
-due to having no nucleus they are unable to divide
-must be constantly replaced by new cells from red bone marrow
how long does erythropoiesis take ?
approx. 7 days
