Transcript Circulatory System of a Mammal

Circulatory System of a
Mammal
The Blood System
• The general pattern of blood circulation in a
mammal. Names are required only of the
coronary arteries and of blood vessels entering
and leaving the heart, liver and kidneys.
• The structure of arteries, arterioles and veins in
relation to their function.
• The structure of capillaries and their importance
in metabolic exchange.
• The formation of tissue fluid and its return to the
circulatory system.
Learning Objectives:
• How do large organisms move substances
around their bodies?
• What are the features of the transport
systems of large organisms?
• How is blood circulated in mammals?
Why do large organisms need a
transport system?
• Increasing size = decrease in the SA to
Volume ratio.
• Can no longer rely on simple diffusion and
need to develop specialist exchange
surfaces
these are linked to
transport systems.
Features of Transport Systems:
• A suitable medium in which to carry
materials.
• A form of mass transport in which the
transport medium is moved around in bulk
over large distances.
• A closed system of tubular vessels that
contains the transport medium.
Features of Transport Systems:
• A mechanism for moving the transport medium
within vessels.
– Muscular contraction of the heart or body muscles.
– Passive processes such as evaporation in plants (see
later lessons).
• A mechanism to maintain the mass flow in one
direction.
• A mechanism of controlling the flow of the
transport medium.
Transport System in Mammals:
• A suitable medium in which to carry
materials - Blood
• A form of mass transport in which the
transport medium is moved around in bulk
over large distances.
• A closed system of tubular vessels that
contains the transport medium – Blood
vessels (arteries, veins and capillaries)
Transport System in Mammals:
• A mechanism for moving the transport
medium within vessels - Muscular
contraction of the heart
• A mechanism to maintain the mass flow in
one direction – valves
• A mechanism of controlling the flow of the
transport medium – heart rate,
vasodilation, vasoconstriction
Single Circulation – e.g. fish
Blood passes through heart
ONCE per complete circuit
Blood pressure reduced as blood passes through the gill
capillaries - slows down flow to the rest of the body
Limits the rate of delivery of O2 and nutrients to cells and
removal of waste
Efficient for the level of activity of fish but not mammals –
also fish do not maintain their body temperature – need to
respire relatively less compared to mammals
Double Circulation – more efficient - e.g. mammals
Heart is composed of two separate pumps – right side pumps
blood to the lungs to pick up oxygen; the blood is returned to
the left side; the left side pumps oxygenated blood rapidly and
at high pressure to the body; the blood is returned to the right
side
Higher level of activity (energy) and need to maintain their
body temperature at 370C – through respiration
Need to deliver and remove materials to and from cells rapidly
– achieved by delivering blood at high pressure to tissues.
Pulmonary – oxygenates blood & removes CO2
Systemic – oxygenated blood from lungs pumped
rapidly at an increased pressure by the heart
Blood passes through heart
TWICE per complete circuit
Questions:
Name the blood vessel in each of the following
descriptions:
1. Joins the right ventricle to the capillaries of the
lungs
2. Carries oxygenated blood away from the heart
3. Carries deoxygenated blood away from the
liver
4. The first main blood vessel that an oxygen
molecule reaches after being absorbed from
an alveolus
5. Has the highest blood pressure
Questions:
1. State two factors that make it more likely
that an organism will have a circulatory
pump such as the heart.
2. What is the main advantage of the
double circulation system found in
mammals?
Blood Vessels and their
Functions
Learning Objectives:
• What are the structures of arteries,
arterioles and veins?
• How is the structure of each of the blood
vessels related to its function?
• What is the structure of capillaries and
how is it related to their function?
Blood Vessels
• Arteries: Carry blood away from the heart
• Arterioles: Control blood flow from arteries
to capillaries
• Capillaries: Link arterioles to veins
• Veins: Carry blood towards the heart
Structure of Blood Vessels
• Tough outer layer –
resists pressure
• Muscle layer – can
contract and control the
flow of blood
• Elastic layer – can stretch
and recoil to maintain
blood pressure
• Endothelium – smooth
layer to prevent friction
• Lumen – not a layer – a
cavity
Structure of Arteries
• Thick muscle layer –
control the flow of
blood
• Thick elastic layer –
smooth surges from
the heart
• No valves
Structure of Arterioles
• Thicker muscle layer
than arteries
• Thinner elastic layer
than arteries
• No valves
Structure of Veins
• Thin muscle layer
• Thin elastic layer
• Valves
Structure of Capillaries
• No muscle
• No elastic
• No valves
• Thin layer of cells
only
Capillary Structure to Function
• Thin layer of cells – short
diffusion distance.
• Numerous and highly
branched – large SA for
diffusion.
• Narrow diameter – keep all
cells close by.
• Narrow lumen – bring RBC
close to the cells = short
diffusion distance.
• Spaces between cells – allow
WBC to escape.
Capillary – endothelium – large number – large surface area for exchange
Wall - one cell thick – short diffusion distance
Endothelium is continuous throughout circulatory system
Capillary
Vein
Wide lumen; Low pressure
Thin wall - less elastic and less muscular
Valves (semilunar) – prevent backflow
Deoxygenated blood to heart from tissues except pulmonary vein from lungs
Non pulsatile – smooth flow of blood
Artery
Narrow lumen; High pressure
Highly elastic – expand and recoil
Thick muscular wall – to withstand force;
more elastic fibres (recoil)
No valves (except aortic and pulmonary
semilunar at the start)
Oxygenated blood from heart – except
pulmonary artery to lungs
Pulsatile blood flow (expansion + recoil)
Pulse can be felt – e.g. wrist
Tissue Fluid
Tissue Fluid
• What is the role of tissue fluid?
It is the fluid which allows the exchange of
substances between the blood and cells
• What substances are found in tissue fluid?
glucose, amino acids, fatty acids, salts and
oxygen = all delivered to the cells.
carbon dioxide and other waste
substances = removed from the cells.
Hydrostatic pressure
Hydrostatic Pressure
• As the capillaries are narrower than the
arterioles, a pressure builds up which forces
tissue fluid out of the blood plasma = hydrostatic
pressure.
• This pressure is resisted by:
– Pressure of the tissue fluid on the capillaries (from the
outside)
– The lower water potential of the blood (caused by
plasma proteins – too large to leave the blood)
• Overall, pressure pushes tissue fluid and small
molecules out of the capillary, leaving cells and
large proteins behind = ultrafiltration.
Return of tissue fluid
• Most tissue fluid is returned to the blood
plasma via the capillaries.
– Hydrostatic pressure at the venule end of the
capillary is higher outside the capillary and
tissue fluid is forced back in.
– Osmotic forces (resulting from the proteins in
the plasma) pull water back into capillaries.
• Remaining tissue fluid enters the lymph
vessels – drain back into the veins close to
the heart.
Lymph System
Lymph
• Lymph is moved by:
– Hydrostatic pressure
– Contraction of body muscles (aided by valves
in the lymph vessels)