Lecture 10 - circulation 1

What does every organism exchange substances with

Its environment

how do exchanges occur at the cellular level

By crossing the plasma membrane

How does exchange occur in unicellular organisms

Directly with the environment via diffusion.

What is the distance of exchange in unicellular organisms

Only across the cell membrane

When does diffusion play an important role

When distances are short (less than 100 um)

What distance does diffusion become ineffective

Over 100 um

In what cells is direct exchange with the environment not possible

Most cells of multicellular organisms.

What do most multicellular cells require for exchange

Specialised transport system.

Fick's law

Rate of diffusion is proportional to;

Surface area x concentration difference

Thickness of membrane

What is diffusion

The movement of molecules from a high concentration to a low concentration

What is osmosis

A special type of diffusion linking to fluids through a semi permeable membrane - the movement o water molecules from a high to a low concentration.

Gas exchange is via _________

Diffusion

Fluid exchange is via _______

Osmosis

Why do we need exchange

Cells have to get rid of waste products.

What are cells engaged in, in multicellular organisms

Metabolic activities.

What does every cell require

• Nutrients

• Oxygen ( if it uses aerobic respiration )

Example of waste products

• Carbon dioxide

• Nitrogenous compounds ( animals )

What is the special transport system in animals

Circulation

3 components of a circulatory system

1. Circulatory fluid

2. Interconnecting vessels

3. Muscular pump.

What does the circulatory system do

Connects the fluid which surrounds cells with the organs that exchange gases, absorb nutrients & dispose of waste products.

What are the 2 types of circulatory system.

Open and closed

Open circulatory system fluid

Hemolymph

What does the hemolymph do in an open circuit

Bathes the body cells and organs.

What is hemolymph composed of

Blood, lymph & interstitial fluid

What organisms have an open circulatory system

Arthropods (eg. Grass hoppers & molluscs)

Describe an open circulatory system

• Heart contractions pump the hemolymph through the circulatory vessels and into the interconnected sinuses (spaces surrounding the organs)

• The hemolymph exchanges gases and other chemicals with body cells within the sinuses

• The heart relaxes, drawing hemolymph back in through pores which have valves that close when the heart contracts

What do body movements cause in an open circulatory system

Periodically squeeze the sinuses which helps to circulate the hemolymph

What does the open circulatory system of larger crustaceans include

More extensive vessels and an accessory pump.

What is the fluid in a closed circulatory system

Blood

Where is the blood in a closed circulatory system

Confined to vessels

What is blood distinct from

Interstitial fluid

What happens in a closed circulatory system

• One or more hearts pump blood into large vessels which branch into smaller ones that infiltrate the tissues and organs

• Chemical exchange occurs between blood and interstitial fluid

• Chemical exchange also occurs between interstitial fluid and body cells

What organisms have a closed circulatory system

Annelids (including earthworms)

Cephalopods (including squid and octopuses)

All vertebrates

What is the pump in a closed circulatory system

Heart

Name of the closed circulatory system in humans

Cardiovascular system

What does the cardiovascular system consist of

Blood, interconnecting vessels arteries, capillaries & veins) & heart

Three types of main blood vessels

1. Arteries

2. Veins

3. Capillaries

What do arteries branch into

Arterioles

What do veins branch into

Venules

What direction do arteries carry blood

Away from heart to the capillaries

What are capillary beds

Networks of capillaries which are the sites of chemical exchange between blood and interstitial fluid

What direction do veins take blood

Towards the heart from the capillaries

How are arteries and veins distinguished

By the direction of blood flow

The two types of vertebrate closed circulatory systems

Single and double

What do single circulatory systems consist of

• One atrium and one ventricle

• Only one circuit

Organisms with a single circulatory system

Bony fish, rays & sharks

Blood pressure level in single systems

Low

What happens in a double circulatory system

Oxygen poor and oxygen rich blood are separately pumped from the left and right sides of the heart

What does a double circulatory system comprise of

• 3-4 heart chambers

• Has 2 loops

Blood pressure level in double circulatory systems

Higher blood pressure than single

Organisms with a double circulation

Amphibians, reptiles, birds and mammals.

Single circulation system in fish

• Deoxygenated Blood is pumped out of the ventricle

• Travels up artery to the gill capillaries where it picks up oxygen

• Oxygenated blood travels to the body capillaries where the oxygen is removed

• Blood returns to the heart via a vein

How many heart chambers do bony fish, rays & sharks have

2: one atrium & one ventricle

What systems are 'in series ‘ within fish circulation

Gill and systemic capillaries

When does blood reach the tissues in fish

After first passing through the gills

Pressure of blood flow in systemic part of fish circulation

Low pressure ( lost at gill capillary)

Ectothermic

Regulate temperature via environmental heat sources

What is blood pressure in the artery of a fish like

High

Where is the high blood pressure lost in a fish

The gill capillaries

Type of circulation in amphibians

Double

How many heart chambers do amphibians have

3: 2 atria and one ventricle

Amphibian circulation

Oxygen poor blood flows through what kind of circuit

Pulmocutaneous circuit to pick up oxygen

How do amphibians breathe

Through nose/mouth and skin

Amphibian circulation blood flow

Ventricle → artery → lung & skin capillaries → vein → ventricle → left atrium → systemic capillaries → right atrium

What does the ridge in the ventricle of amphibians do

Diverts majority of the oxygen-rich blood into the systemic circuit (bottom) & most of the oxygen poor blood into the pulmocutaneous circuit (top)

Is blood in the ventricle of an amphibian oxygenated

There is some mixing of oxygenated & deoxygenated

When do amphibians breathe via the skin

Blood flow to the lungs is nearly shut off when underwater

Type of circulation in reptiles

Double

How many heart chambers do reptiles have

2 atria and one ventricle (except from crocodilians which have 2 atria & 2 ventricles)

Do reptiles have a septum

An incomplete septum

How many aortas do reptiles have

2

Blood flow in reptiles

Left ventricle side → aorta → body capillaries (systemic circulation) → right atrium → right ventricle → lung capillaries (pulmonary circulation) → left atrium

Circulation in mammals & birds

Double

How many heart chambers do mammals & birds have

4: 2 atria & 2 ventricles

What do the left and right sides of the heart in mammals & birds do

• left: receives and pumps oxygen rich blood

• Right: receives and pumps oxygen poor blood

Blood flow in mammals and birds

Right ventricle → lung capillaries (pulmonary circuit) → left atrium → left ventricle → systemic capillaries (systemic circuit) → right atrium

Mammals & birds are endothermic what does this mean

They require more oxygen as they have to generate their own heat

Do mammals and birds have a septum

Yes: the ventricles are separated

What is the human circulatory system composed of

Four contracting chambers and 2 loops of blood vessels

2 types of circulation systems in humans

Pulmonary and systemic

What are the blood distribution percentages in humans

• Heart = 7%

• Pulmonary circulation = 9%

• Systemic circulation = 84%

Blood distribution in the systemic circulation

• Arterioles and capillaries = 7%

• Arteries = 13%

• Veins, venues and venous sinuses = 64%

Structure and function of human atria

• Have very thin walls

• Collect the blood that is returning to heart and allow it to trickle down into the ventricles

Structure and function of human ventricles

• Thicker wall

• Contract more forcefully

• Right one pumps blood to the pulmonary circulation

• Left one pumps blood to the systemic circulation so has a higher pressure and thicker muscular wall than right

The cardiac cycle

The rhythmic cycle of heart contractions and relaxing

Name of the contracting phase of the cardiac cycle

Systole

Right atrium

Receives deoxygenated blood from the body (systemic circulation)

Right ventricle

Pumps deoxygenated blood to the lungs via the pulmonary arteries (pulmonary circulation)

Left atrium

Receives oxygenated blood from pulmonary veins

Left ventricle

Pumps oxygenated blood to the body via the aorta

Function of valves

Ensures blood flows in the correct direction by preventing the backflow

What causes the lub- dub sound on a stethoscope

Closure of valves

What is a heart murmur

Extra sounds on a stethoscope (e.g. The backflow of blood through a defective valve)

The atrioventricular valves

• Tricuspid valve: between right atrium and ventricle

• Mitral valve: between left atrium and ventricle

Semilunar valves

• Aortic: between left ventricle and aorta

• Pulmonary: between right ventricle and pulmonary valve