Circulation [part 1]
Transcript of Circulation [part 1]
TRANSPORT IN ANIMALS [part 1]
A) General characteristics of a circulatory system
B) The development of blood systems in animals
C) Composition of blood
D) The circulatory system
E) Formation of tissue fluid
F) The heart
G) Functions of mammalian blood
H) Oxygen dissociation curves – The Bohr shift
A) General characteristics of a circulatory system
B) The development of blood systems in animals
C) Composition of blood
D) The circulatory system
E) Formation of tissue fluid
F) The heart
G) Functions of mammalian blood
H) Oxygen dissociation curves – The Bohr shift
Function of a circulatory system:
To provide rapid mass flow of materials:
Blood flow
Vein
from one part of the body
to another over distances where
diffusion would be too slow
On reaching their destination, materials must be able to:
pass through the walls of the circulatory system into the organs or tissues
Three distinct characteristics of every blood system:
1. a circulatory fluid, the blood
2. a contractile pumping devise [either a modified blood vessel or a heart]
3. tubes through which the fluid can circulate, the blood vessels
Two distinct types of blood systems in animals:
Open circulation Closed circulation
blood does not stay
in the blood vesselsblood stays in the
blood vessels
most arthropods
Open circulation in Closed circulation in
echinoderms
most cephalopod
molluscs (octopus)
annelids
vertebratessome molluscs
Distribution of blood to the tissues is :
poorly controlled
Open circulation Closed circulation
well controlled
Blood and tissue fluid in:
mix
Open circulation
Closed circulation
remain separate
In an open circulation:1. The heart pumps blood into
an aorta: branches into
arteries.
2. These arteries open into a
series of blood spaces
collectively called the
haemocoel.
3. Blood under low pressure
moves slowly between the
tissues, gradually percolating
back into the heart through
open-ended veins.
In a closed circulation blood is:
pumped by the heart rapidly around the body under high pressure and back to the heart
Characteristics of:Open circulation Closed circulation1. Blood flow is slow and at a low pressure due to the absence of smooth muscles.
1. The speed of circulation is more rapid due to the presence of muscular and contractile blood vessels.
2. Direct exchange of materials between the cells and the blood because of the direct contact between them.
2. The supply and removal of materials to and from the tissues by the blood is enhanced, thereby increasing the efficiency of circulation.
3. The respiratory pigment, when present, is dissolved in the plasma of the blood and there are no red corpuscles
3. The volume of blood flowing through a tissue or organ is regulated by the contraction and relaxation of the muscles of the blood vessels.
Advantages of a closed circulation:
1. Blood can flow more rapidly through vessels
than through intercellular spaces, so:
rapid transport of nutrients and wastes
to and from tissues more rapidly.
A closed circulation:
can support higher levels of metabolic activity than open systems, especially
in larger animals
Insects do not depend on their circulation for O2 to reach the cells, but have the tracheal
system.
How can highly active insect species achieve high levels of metabolic output with their open
circulatory system?
Advantages of a closed circulation:2. By changing resistances in the blood vessels, blood
can be directed to specific tissues
e.g. during
exercise blood
is:
diverted to:
active
muscles
away from:
the gut
Advantages of a closed circulation:
3.
can be kept
within the
vessels
Cellular elements
Large molecules that
aid in the transport of
hormones
Nutrients
A) General characteristics of a circulatory system
B) The development of blood systems in animals
C) Composition of blood
D) The circulatory system
E) Formation of tissue fluid
F) The heart
G) Functions of mammalian blood
H) Oxygen dissociation curves – The Bohr shift
Annelids (fig. 2)
are coelomate animals
separates the body
wall from the internal
organs
independence of movement of internal structures such as the gut
a blood system has evolved which connects gut and body wall
However, a connecting system between the two
regions is needed
The earthworm:has a well-developed blood system
blood circulates in blood vessels
2 main blood vessels: run the length of the
body: one dorsal one ventral
are connected by blood vessels in each segment
1. Near the front of the animal:
5 pairs of connecting vessels are contractile and act as pumps
How is blood moved forwards in an earthworm?
5 hearts
2. The main blood vessels can also pump blood.
contains haemoglobin dissolved in the plasma rather than in red blood cells
Blood in an earthworm:
Arthropods (fig. 3a) : have an open blood system
the coelom is drastically reduced
and its place taken by the haemocoel
What is the ‘haemocoel’?
Crayfish
Haemocoel
The haemocoel is a network of blood-filled spaces called sinuses in which the
internal organs are suspended.
Crayfish
Haemocoel
Sinus
Arthropod blood is:
colourless contains no haemoglobin
The insect’s heart is a flexible tube and runs:1. longitudinally
through the thorax
& abdomen Heart
2. along the inside of the dorsal
body wall
A small valve-like opening through which blood enters
the heart
The dorsal vessel is:
Dorsal vessel is called
HEART in the abdomen
closed at the
posterior end
open at the
anterior end
The heart is divided
into chambers
separated by ostia Heart
13 chambers in
cockroach
Does not possess :
- valves
- musculature
Is a simple tube
Each chamber has a pair of:alary muscles
expand & contract to facilitate the flow of haemolymph through the heart
Position of heart in vertebrates:
ventral position near the front of the animal
Vertebrates:
arteries carry blood away from the heart
veins carry blood back to the heart
O2 is carried by
haemoglobin in red blood cells
A) General characteristics of a circulatory system
B) The development of blood systems in animals
C) Composition of bloodD) The circulatory system
E) Formation of tissue fluid
F) The heart
G) Functions of mammalian blood
H) Oxygen dissociation curves – The Bohr shift
Blood is:a liquid tissue made up of several types
of cell which are bathed in plasma
Whole Blood Sample
Sample Placed in Centrifuge
Blood Sample That Has Been
Centrifuged
Plasma
PlateletsWhite blood cells
Red blood cells
Platelets
White blood cells
Red blood cells
plasma
Percentage by volume of:
What is ‘serum’?
plasma without fibrinogen
Plasma is:
a pale straw-coloured liquid
made up of: 90% water 10% substances
Constituents of PLASMA Major FunctionsWater Solvent for carrying other
substancesSalts
SodiumPotassiumCalciumMagnesiumChlorideHydrogen carbonate
Osmotic balance,pH buffering, Regulation of membrane permeability
Plasma ProteinsAlbuminFibrinogenAntibodies
Osmotic balance,pH buffering,Clotting,Immunity
Substances transported by bloodNutrients (e.g. glucose, vitamins)Waste products of metabolismRespiratory gasesHormones
CELLULAR ELEMENTS 45%
CELL TYPE NUMBER(per mm3 of blood)
FUNCTIONS
Erythrocytes(red blood cells)
5–6 million
Transport ofoxygen (and carbon dioxide)
Leucocytes(white blood cells) 5,000–10,000
Defence andimmunity
Basophil
Eosinophil
Neutrophil
Lymphocyte
Monocyte
Platelets
250,000–400,000 Blood clotting
Where are blood cells formed?
Pluripotent stem cells in the red marrow of bones
Platelets
Pluripotent: capable of giving rise to
several different cell types
PlateletsRed blood cells
White blood cells
B cells T cells
Lymphoidstem cells
Pluripotent stem cells(in bone marrow)
Myeloidstem cells
Erythrocytes
Platelets Monocytes
Neutrophils
Eosinophils
Basophils
Lymphocytes
What is ?A hormone made by:
Kidneys
Released when:
Oxygen levels are low
Causes:
RBC formation
Negative Feedback
Control
RED BLOOD CELLS
ERYTHROCYTES
RBCsmall biconcave discs
surface area efficiency for diffusion of
O2 & CO2
lack a nucleus when mature
very thin cells: efficient diffusion of gases across surface
RBC are flexible & elastic:
to squeeze through narrow capillaries
Cardiac muscle and capillary
Erythrocytes in single file – capillary is so narrow
RBC make up about half the volume of blood
i.e. blood has an enormous oxygen-carrying capacity
Erythrocytes(45% of total blood)
Plasma(55% of total blood)
Leucocytes & Platelets(< 1% of total blood)
haemoglobin: the oxygen-carrying protein pigment combines reversibly with O2
RBC: packed with haemoglobin
Haem
Haemoglobin
Hb + O2 :
- in areas of high O2 concentration
Hb releases the O2 :
- in regions of low O2 concentration
Oxyhaemoglobin
LOADING
UNLOADING
RBC lack mitochondria. Give two advantages of this.
1. more room for carrying haemoglobin
2. respire anaerobically : do not use up any of the O2 they carry
RBC contain the enzyme:
plays a role in CO2 transport
carbonic anhydrase
Life span of RBC
about 3 months
then destroyed in: liver or spleen
What happens to haemoglobin when an old RBC is broken down?
Protein portion:
amino acids
Iron in haem:
stored in liver as ferritin (an iron-
containing protein)
Remainder of the haem molecule:
broken down into two bile pigments
(bilirubin and biliverdin)
White blood cellshave a nucleus
larger than RBC
present in smaller amounts
life span is normally a few days
A blood smear
All WBC are capable of a:
crawling movement called amoeboid movement
Lecuocytes can be divided:
Granulocytes Agranulocytes
Lymphocyte
Neutrophil
Basophil
Eosinophil
Monocyte
Lobed nucleus
Oval or bean-shaped nucleus
72% of total WBC count 28%
Neutrophils:70% of WBCs
Function Phagocytise & destroy
bacteria
Lobed
nucleus
First cells to respond to infection
Eosinophils:
1.5% of WBCs but numbers increase with allergic conditions
Function:
Secrete antihistamine
Eosin-staining granules
Basophils:
0.5% of all white blood cells
granules stain blue with basic dyes such as methylene blue
Function:
produce: heparin (anti-clotting protein) histamine (involved in inflammation)
Monocytes:spend 30-40 hours in
the blood then enter the tissues where they become macrophages
macrophages:
are phagocytic
Lymphocytes: produced in:
thymus gland lymphoid tissues
from cells which originate in the bone
marrow
Lymphocytes:
are rounded have a small quantity of cytoplasm
Considering the shape of the lymphocyte, do you expect amoeboid movement to be extensive or limited?
Limited
are found in:
Lymphocytes:blood
lymph
body tissues
two types occur: T cells B cells
life span varies from: a matter of days to many years
involved in immune reactions
Fig. 22.12Stem cell
B cell
T cell
B cell
T cell
Red bone marrow
Circulation
Pre-B cell
Pre-T cell
Circulation
Pre-T cell
Thymus Lymphnode
Circulation
Platelets:
irregularly shapedmembrane-bound cell
fragmentusually lacking nuclei
life span: 5-9 days before
destruction in liver & spleen
Platelets are formed from:special cells (megakaryocytes) in the
bone marrow
Function of Platelets:start the clotting process
Break in Capillary
Wall
Clumping of Platelets Clot forms
Fibrin fibres
Practical work to include the microscopic examination of stained
blood films and the identification of cells.
LymphocyteNeutrophils
Platelets Erythrocytes Monocyte
A) General characteristics of a circulatory system
B) The development of blood systems in animals
C) Composition of blood
D) The circulatory systemE) Formation of tissue fluid
F) The heart
G) Functions of mammalian blood
H) Oxygen dissociation curves – The Bohr shift
Three features of human circulation:
1. It is a double circulation. pressure is restored &
boosted before the blood is circulated to the rest of the body
Pulmonary circulation:
through lungs
SystemicCirculation:
through the rest of the body
Pulmonary vein
Aorta
Hepatic artery
Renal arteryRenal vein
Hepatic portal vein
Vena cava
Pulmonary artery
2. The organs are arranged in parallel rather than in series. loss in pressure, oxygen and nutrients at each
stage – if in series
Pulmonary vein
Aorta
Hepatic artery
Renal arteryRenal vein
Hepatic portal vein
Vena cava
Pulmonary artery
3. A portal vessel links the gut to the liver. the liver monitors blood passing
through it to help keep a constant composition
Double circulation of blood in humans
blood passes through the heart twice for each circuit of the body
Single circulation
Double circulation
FISH
BIRDS & MAMMALS have true double
circulations
the beginnings of a double circulation are seen in amphibians
reptiles have an almost completely divided heart
Why is a single circulation less efficient than a double circulation?
Drop in pressure as blood passes through the gills
Three layers in an artery & a vein
1. Tunica intima [endothelium]
an inner lining of squamous epithelium
2. Tunica media a middle layer of
smooth muscle + elastic fibres
3. Tunica externa an external layer
consisting mainly of inelastic collagen fibres)
Compare anatomy of:
Artery
VeinNote the much thinner walls in veins.
Artery and Vein
Two reasons for walls of arteries being thick and the middle layer being mainly composed of elastic
fibres.
1. To dilate but not rupture when the heart forces blood into them at high pressure
2. Between beats the arteries undergo elastic recoil and contract, tending to smooth out the flow of blood along their length
Muscles in blood vessels regulate the distribution of blood to an organ:
Normal arteriole
Vasoconstriction
Resistance = Decreased flow
Resistance =
Vasodilation
Caused by:
CO2
Cold
CO2
HeatIncreased flow
Veinsact as blood reservoirsstore: 65% - 70% of the body’s total
blood volume
Veins contain one-way valves
Varicose Veins:Damaged valves
in veins
When body muscles contract, they exert
pressure and squeeze the veins
flat, helping the blood to return to the heart.
How does blood return to the heart?
Capillaries• are very small - about the
diameter of a red blood cell
• capillary walls are: a single layer of very thin
endothelial cells, attached at their edges
and surrounded by a basement membrane
Endothelial cells
Question: Section C [MAY, 2010]
Use your knowledge of biology to describe the selective advantage of the following adaptations.
The diameters of red blood cells and the blood capillaries in which they flow are approximately the same. (5 marks)
Basement membrane
Blood moves slowly in capillaries as the diameter of RBC is approximately the same as that of capillaries. This gives time for:
oxygen to be released from RBC and to diffuse into the tissue fluid.
another function of RBC is to carry carbon dioxide away from tissues in the form of carbamino-haemoglobin. Ample time is available for carbon dioxide to enter the RBC.
Flow of blood into capillaries can be controlled by:
sphincters present in many arterioles at the point where they
enter the capillaries
Sphincters are circular muscle fibres:
When contracted: prevent blood flow into the capillary network
Pressure is reduced in smaller vessels because:
Arterioles are highly branched.Capillaries contribute an enormous
surface area.
Fig. 16 Blood pressure throughout the human circulatory system.
Blood flows slowly through capillaries. Why?
Due to a very large cross-sectional area[velocity is inversely proportional to cross-
sectional area
Capillary beds are:
permeable to:
water, ions, small molecules
impermeable to:
large proteins
Blood cells, most proteins.
Vesicles; large, lipid-insoluble (proteins)Filtration; fluid and
small, lipid-insoluble molecules (water, amino acids,NaCl, glucose,urea)
Diffusion; lipid-soluble molecules(O2, CO2, lipids)
Label the veins, venules, arteries, arterioles, and capillaries
Across which vessels do materials diffuse (cross into and out of the blood)?
Indicate where the heart is
veinvenules
artery
arteriolescapillaries
Artery Vein CapillaryTransports blood away from the heart.
Transports blood towards the heart.
Link arteries to veins
Tunica media thick and composed of elastic and smooth muscle tissue.
Tunica media relatively thin and only slightly muscular. Few elastic fibres.
No tunica media. Only tissue present is squamous endothelium. No elastic fibres.
Artery Vein CapillaryNo semilunar valves (except where leave heart).
Semilunar valves at intervals along the length to prevent backflow of blood.
No semilunar valves.
Pressure of blood is high and has a pulse.
Pressure of blood low and no pulse detectable.
Pressure of blood falling and no pulse detectable.
Artery Vein CapillaryBlood flow rapid. Blood flow slow. Blood flow
slowing.Low blood volume. Much higher blood
volume than capillaries or arteries.
High blood volume.
Blood oxygenated except in pulmonary artery.
Blood deoxygenated except in pulmonary vein.
Mixed: oxygenated & deoxygenated blood.
A) General characteristics of a circulatory system
B) The development of blood systems in animals
C) Composition of blood
D) The circulatory system
E) Formation of tissue fluidF) The heart
G) Functions of mammalian blood
H) Oxygen dissociation curves – The Bohr shift
Tissue fluid: forms by filtration when blood passes through
capillaries is a watery liquid that resembles plasma minus its
proteins
Tissue cell
Capillary
Tissue fluid forms Tissue fluid
returns
Direction of blood flow
Arterial end of capillary
Venous end of capillary
15 µm
What forces are involved in tissue fluid formation?
two opposing forces :
Blood pressure forces water and small solutes out
Osmotic pressure
created by the large molecules that cannot leave (also called colloidal osmotic pressure)
Arterial end Venous end
Formation & drainage of tissue fluid
What can you say about the collodial osmotic pressure value?
is relatively constant along the capillary
Blood, tissue fluid & lymph
10%
90%
Kwashiorkor (protein deficiency) results in the swelling (oedema) of the belly
an osmotic effect
the ability of the blood to take up water from the body cavity by osmosis is reduced because of the deficiency of blood proteins (solutes)
An extensive system of blind-ending tubes which carries lymph
What is the Lymphatic System?
Lymph is:a clear, watery, sometimes faintly
yellowish fluid derived from tissue fluid
similar in composition to blood plasma
1. does not contain erythrocytes
2. contains a much lower concentration of protein
The Lymphatic System consists of: Lymphatic
vessels Lymphoid tissues
and organs
[Lymphoid tissue: where
lymphocytes develop e.g.
lymph nodes]
Lymph nodes occur all over the body
600-700 lymph nodes
Lymph contains white blood cells
Lymphocytes in lymph node
Three functions of the lymphatic system:
1. Removes excess tissue fluid from tissues
2. Absorbs and transports fats from the digestive system
Blood capillary
Thin epithelium
Lacteal (lymphatic
vessel)
3. Plays a role in immunity.
A lymph node filters microbes.
How does lymph return to the blood? Via the:
right
lymphatic duct
left thoracic duct
Both the circulatory & the lymphatic system possess:
Unidirectional or
bidirectional flow of lymph?
How is lymph moved through lymph vessels?
By contraction of the muscles surrounding
them
By semi-lunar valves present in the major vessels
How is backflow prevented?
What happens if the lymphatic vessels become blocked as by parasitic worms?
A nematode worm infects the lymph nodes and
blocks the flow of lymph throughout the body.
Elephantiasis Disease or Filariasis:
transmitted by a mosquito bite
[over 130 million people are
infected]
Wuchereria bancrofti
Female worms: 8 -10 cm long Males: 4 cm
This question is concerned with the lymphatic system.
a. What is lymph? (2)
Lymph, a colorless to yellowish fluid whose composition is similar to that of blood except that it does not contain red blood cells or platelets, and contains considerably less protein.
Question: [SEP, 2009]
b. What are the main functions of the lymphatic system? (2)
- collects fats from the ileum via lacteals
- plays a role in immunity. Fluid is filtered in lymph nodes which contain lymphocytes that kill microbes
- drains tissue fluid and returns it to the bloodstream.
c. Briefly describe how fluid enters and leaves the lymphatic system. (3)
Tissue fluid enters the lymphatic system located at the venous end of a capillary. Lymph is drained into the subclavian vein by the right or thoracic lymph ducts.
d. Compare the composition of lymph with that of blood plasma in the following two situations:
i) Lymph that has just left a lymph node; (1)
Lymph is richer in lymphocytes than plasma as it leaves the lymph nodes.
ii) Lymph formed in the vicinity of the small intestine.
Is rich in fats as lacteals absorb triglycerides. (1)
e. How is lymph propelled through the lymphatic system? (2)
By contractions of skeletal muscles. Valves inside the lymphatic vessels prevent backflow.