1. Gamete production and fertilisation
a) Gamete production in the testes
Male reproductive system
Seminiferous tubules unite to form sperm duct.
Testes
Prostate gland & seminal vesicles secrete fluids that maintain mobility and viability of sperm.
Produce sperm in seminiferous tubules
produce testosterone in interstitial cells
1. Gamete production and fertilisation
b) Gamete production in the ovaries
Female reproductive system
Each ovum is surrounded by a follicle that protects the developing ovum and secretes hormones.
Eggs are formed from germline cells in the ovaries.
Ovaries contain immature ova (eggs) in various stages of development.
1. GAMETE PRODUCTION AND FERTILISATION
c) Fertilisation
Fertilisation
Mature ova are released into the oviduct where they may be fertilised by a sperm to form a zygote
2. Hormonal control of reproduction
a) Hormonal influence on puberty
Hormones - chemical messengers produced by endocrine glands and secreted into the blood.
Triggers a specific effect in its target tissue.
Hormonal onset of puberty
The hypothalamus secretes a releaser hormone which targets the pituitary gland and triggers the onset of puberty.
The pituitary gland is then stimulated to release
or
2. Hormonal control of reproduction
b) Hormonal control of sperm production
Pituitary gland
FSH promotes sperm production
ICSH stimulates production of testosterone
Testosterone
- stimulates sperm production
- Activates prostate gland and seminal vesicles
Inhibition
(negative feedback )
High levels of testosterone
FIT
Hormonal control of sperm production
Secretion of FSH and ICSH by the pituitary is inhibited
Negative feedback control
As testosterone concentration increases, FSH + ICSH production is inhibited until testosterone concentration decreases.
stimulates sperm production.
promotes sperm production in seminiferous tubules
stimulates testosterone production
Hormonal control of sperm production
FIT
FSH
ICSH
TESTOSTERONE
Activates prostate and seminal vesicles.
Match the correct function to the correct hormone
2. Hormonal control of reproduction
c) Hormonal control of the menstrual cycle
The Menstrual Cycle
FSH
Follicular phase
FOLP
Hormonal control of the menstrual cycle – pituitary hormones
LH
Luteal phase
Secretion of oestrogen
Secretion of progesterone
2. follicle develops into a corpus luteum and secretes progesterone
1. triggers ovulation – release of an egg from a follicle
Ovulation
Ovulation is the release of an egg (ovum) from a follicle in the ovary.
It usually occurs around the mid-point of the menstrual cycle.
FOLP
Hormonal control of the menstrual cycle
– Ovarian hormones
Hormonal control of the menstrual cycle
– Ovarian hormones
FOLP
Negative feedback effect of ovarian hormones on the pituitary
High levels of progesterone inhibits secretion of FSH + LH by pituitary to prevent further follicles from developing
FOLP
Menstruation
If fertilisation does not take place, a lack of LH leads to degeneration of corpus luteum. This is followed by a rapid drop in progesterone levels leading to menstruation
If fertilisation does occur……
The embryo secretes a hormone that maintains the corpus luteum.
It continues to secrete progesterone which prevents menstruation from taking place.
After about six weeks the placenta takes on the job of secreting progesterone.
The menstrual cycle�
Day 1 - menstruation
Follicular phase
Luteal phase
(follows ovulation)
FOLP
stimulates development of a follicle and follicle produces oestrogen
triggers ovulation
follicle develops into a corpus luteum and secretes progesterone
stimulates proliferation of endometrium
promotes vascularisation of endometrium
High levels of progesterone inhibits secretion of FSH + LH
Peak oestrogen stimulates LH secretion
Hormonal control of the menstrual cycle summary
Menstruation
Follicular phase
Luteal phase
Ovulation
If fertilisation and implantation does not take place progesterone and oestrogen levels decrease
Pituitary gland secretes FSH
Follicle secretes oestrogen
Pituitary gland secretes LH
Corpus luteum secretes progesterone
Hormone | Site of production | Function |
FSH | Pituitary gland |
|
LH | Pituitary gland |
|
Oestrogen | Ovaries |
|
Progesterone | Ovaries |
|
3. The biology of controlling fertility
a) Fertility
Fertile periods |
Infertility treatments and contraception are based on the biology of fertility
The negative feedback effect of testosterone maintains a constant level of FSH and ICSH in the blood.
This results in a steady production of testosterone and therefore sperm which means men are continuously fertile.
The levels of pituitary and ovarian hormones in the body results in a period of cyclical fertility in women restricted to 1-2 days immediately following ovulation
Menstruation
Ovulation
Identification of the fertile period
Body temperature rises by around 0.5oC following ovulation, under the action of progesterone.
Temperature
Cervical mucus during the fertile period is thin and watery to allow sperm easy access.
After ovulation, mucus increases in viscosity again.
Mucus
Indicators used to calculate the fertile period when sexual intercourse is likely to achieve fertilisation.
3. The biology of controlling fertility
b) Treatments for infertility
Fertility can be affected by….
What factors may affect your fertility?
Age
Genetics
Disease
Poor diet
Stress
Obesity
Drug misuse
Smoking
Anorexia
For fertilisation and implantation to occur, viable gametes must be produced and the following events must be possible…..
Treatments for infertility |
Failure to ovulate may be due to underlying factors such as failure of the pituitary gland.
Ovulation can be stimulated by
These drugs can bring about multiple ovulation and lead to multiple births or be used to collect ova for IVF programmes.
2. Artificial insemination
Treatments for infertility |
Introduction of semen into female reproductive tract by means other than sexual intercourse.
If a male has a low sperm count then several samples are collected and frozen until required. Then defrosted and released into the partners cervix when they are likely to be fertile.
�If the male is infertile, a donor can be used to provide semen.
3. Intracytoplasmic sperm injection
Treatments for infertility |
Used if mature sperm are defective or very low in number. �
The head of a healthy sperm is drawn into a needle and injected directly into an egg.
The egg is held in place by a holding tool.
Treatments for infertility |
4. In vitro fertilisation (IVF)
Used to overcome blockage of the oviducts.
Fertilisation outside the body in a culture dish
Hormonal treatment to stimulates multiple ovulations
eggs surgically removed
eggs are mixed with sperm in culture dish to allow fertilisation
zygotes are incubated until they have formed at least 8 cells
2/3 embryos inserted into mothers uterus for implantation
remaining embryos frozen
Pre-implantation genetic screening and diagnosis
This can be used in conjunction with IVF to identify single gene disorders and chromosomal abnormalities
Prior to implantation, one or more cells may be removed and tested for genetic abnormalities.
The test allow experts to select which embryos should and should be not be implanted .
3. The biology of controlling fertility
c) Physical and chemical methods of contraception
Contraception |
Intentional prevention of conception or pregnancy by natural or artificial means.
Intra-uterine devices
An IUD is a T-shaped plastic and copper device placed into the uterus for many months/years to prevent implantation of an embryo
The copper is toxic to sperm and prevents fertilisation or implantation
Vasectomy - cutting and tying of the sperm ducts to prevent release of sperm. Sperm produced thereafter are destroyed by phagocytosis
Tubal ligation - cutting and tying of the two oviducts to prevent eggs meeting sperm and reaching the uterus. Highly effective and irreversible.
Sterilisation procedures
Chemical methods of contraception
The oral contraceptive pill is chemical method of contraception. It contains a combination of synthetic oestrogen and progesterone.
This mimics negative feedback preventing FSH + LH release from the pituitary.
Emergency hormonal contraceptive pills (morning after pill)
Pills containing a combination of hormones
Can be taken up to 72 – 120 hours (depending on the pill) after unprotected sex to prevent or delay ovulation.
(mini) pills (progesterone only)
Causes thickening of cervical mucus to reduce access to the uterus.
| A | B | C | D |
Total number of sperm (millions/cm3) | 25 | 30 | 35 | 40 |
Number of active sperm (millions/cm3) | 10 | 11 | 15 | 18 |
Number of normal sperm (million/cm3) | 15 | 16 | 22 | 24 |
Patient
Question
The data in the table refers to four patients attending a fertility clinic.
The clinic considers a man to be fertile if
Which patient in the table fails to meet these criteria fully?
Answer
B
Production of sperm
Transport of sperm out of body
Arrival of sperm in vagina
Movement of sperm through uterus and oviducts
Production of ova
Ovulation
Entry of ovum into oviduct
Movement of ovum in oviduct
Meeting and fusion of ovum and sperm
Implantation of embryo in endometrium
Methods initiated by men
Methods initiated by women
Each arrow indicates the point at which a certain method of contraception may act and prevent the sequence of events leading to implantation from occurring.
Match arrows 1 – 6 with the following methods of contraception;
condom, combined contraceptive pill, diaphragm, IUD, ligation of oviducts and vasectomy.
1
3
2
4
5
6
Condom
Contraceptive pill
Vasectomy
Ligation of oviducts
Diaphragm
IUD
4. Antenatal and post natal screening
a) Antenatal screening
A variety of techniques can be used to monitor the health of the mother and her foetus.
Antenatal screening identifies the risk of a disorder so that further tests and a prenatal diagnosis can be offered.
Antenatal care
Ultrasound imaging
Pregnant women are given two ultrasound scans.
Dating scan
Carried out at 8-14 weeks to determine stage of pregnancy (gestational age) and due date.
Used in conjunction with biochemical tests for marker chemicals which vary normally during pregnancy.
Anomaly scan
Performed at 18-20 weeks to check for the presence of any serious physical abnormalities of the limbs and organs of the foetus.
Biochemical tests
Routine blood and urine tests carried out throughout pregnancy to monitor the concentrations of marker chemicals.
False positive and false negatives
Some conditions are indicated by presence of certain marker chemicals in blood and urine.
These marker chemicals vary during pregnancy.
In a normal pregnancy HCG levels increase during weeks 6-10 and then decrease to a steady lower level later in pregnancy. However, if this chemical level remains elevated, the foetus may have down syndrome.
Measuring the chemical at the wrong time (10 weeks) produces a false positive result as the test would show the foetus has a condition when it does not.
If test is carried out and found to be low at a time when the normal value is low this could provide a false negative and suggest the foetus does not have the condition when it maybe does.
This table shows the data from an investigation into the effectiveness of ultrasound imaging on the antenatal detection of inherited malformations in babies born in a region of the UK.
The results in row 3 are examples of false positives because the screening for malformations has produced results indicating that these foetuses had inherited malformations when in fact the babies were found to be normal at birth.
Row 4 are examples of false negatives as the screening produced results indicating that the foetuses had not inherited malformations when in fact the babies did have them at birth.
False positive and false negatives
At 16-18 weeks a woman is offered a test to check for AFP (alpha-fetoprotein). The concentration in mother's blood increases whilst pregnant and decreases after the baby is born.
�
Low levels of AFP (<0.5) (0.5-2.49 normal) are found in cases of Down’s syndrome.
Result of this screening test in conjunction with the mother's age and a nuchal translucency scan (measuring the thickness of the fluid at the nape of the foetus’ neck) allow experts to assess the likelihood of chromosomal abnormalities present in the foetus and indicates the need for further diagnostic testing.
Biochemical tests
An atypical (unusual) chemical concentration can lead to diagnostic testing to determine if the foetus has a medical condition.
Normal
Abnormal
Diagnostic testing
A definitive test used to establish whether or not a person is suffering a specific condition or disorder.
Can be offered if there is;
A persons karyotype is a visual display of their chromosomes arranged as homologous pairs.
Amniocentesis and CVS are diagnostic tests which use foetal material to allow a karyotype to be prepared for examination.
Diagnostic testing
Examine these karyotypes and find out what genetic disorders they indicate.
Write a short note on each one.
Amniocentesis
Carried out about 14-16 weeks.
Involves withdrawal of amniotic fluid containing foetal cells.
Lower risk of miscarriage (1%).
Cells from the samples are cultured, stained and examined under the microscope to produce a karyotype.
Allows diagnosis of a range
of conditions.
Chorionic villus sampling
Carried out as early as 8 weeks.
Sample of placental cells taken and cultured and used for karyotyping.
Prospect of termination at this point is much less traumatic but incidence of miscarriage is much higher (2%).
When deciding to proceed with these tests, the element of risk is assessed as is the decisions the individuals concerned need to make if the test is positive.
4. Antenatal and post natal screening
b) Analysis of patterns of inheritance in genetic screening and counselling
GENETICS TERMS
alleles
dominant
recessive
homozygous
heterozygous
carriers
genotype
phenotype
autosomes
Sex chromosomes
Can you remember the definitions of these terms?
Copy them into your jotter and use the textbook to write the correct definition beside each term.
Analysis of patterns of inheritance
X and Y chromosomes - sex chromosomes.
All other chromosomes - autosomes.
These are the most commonly used terms/symbols for human pedigree charts
Mating line
Male parent
Female parent
Homozygous genotype
Line of descent
Twins
Deceased male
Heterozygous genotype
A pattern of inheritance can be revealed by constructing a family tree.
Once phenotypes are known, genotypes can be deduced by a genetic counsellor when there are concerns about passing a genetic disorder in a family on to the children.
Autosomal recessive inheritance
Autosomal dominant inheritance
Autosomal incomplete dominance
Sex-linked recessive trait
Answer questions 5,6 and 7 on pgs. 152-153 from the textbook
4. Antenatal and post natal screening
c) Post natal screening
Post natal screening
Postnatal screening involves health checks carried out after the birth of a baby, aimed at detecting certain conditions or abnormalities.
New-borns babies are screened for PKU, hypothyroidism, CF and galactosaemia in the heel prick test.
Post natal screening
Affected individuals are placed on a reduced phenylalanine diet to prevent high levels affecting brain development.
PKU (an inborn error of metabolism) is a substitution mutation. As a result, the enzyme which converts phenylalanine to tyrosine is non-functional. If not detected soon after birth, mental development is adversely affected.
Phenylalanine
metabolite X
Tyrosine
enzyme 1
enzyme 2
gene 2
gene 1
mutation
X
X
5. Structure and functions of arteries, capillaries and veins
a) Blood circulation
What can you remember from N5 about blood and blood vessels?
Circulation
Blood circulates from the heart through the arteries to the capillaries and then to veins and back to the heart.
There is a decrease in pressure as blood moves away from the heart.
Heart
Arteries
Capillaries
Arterioles
Venules
Veins
Pressure - 120mmHg
Pressure - almost 0mmHg
5. Structure and functions of arteries, capillaries and veins
b) The structure and function of arteries, capillaries and veins
Blood vessels - Arteries
The central space within a blood vessel is called the lumen. The lumen of an artery is lined with a thin layer of cells called the endothelium.
Outer layer of connective tissue containing elastic fibres
Middle layer containing smooth muscle with more elastic fibres
Lining of endothelium
To control blood flow, the smooth muscle in the middle layer of arteries can
This allows the demands of different tissues to be met by adjusting distribution of blood
Vasoconstriction and vasodilation
Example
During strenuous exercise, arteries to the muscles vasodilate to increase blood flow to skeletal muscles and arteries to abdominal organs undergo vasoconstriction to reduce blood flow to these parts.
Blood vessels – Veins
Outer layer of connective tissue containing elastic fibres
Muscular layers of elastic fibres are thinner than arteries.
valves prevent backflow of blood
The lumen of a vein is wide compared to arteries.
Demonstrating the presence of valves in veins
Measuring the degree of stretching in arteries and veins
The rings of an artery and vein are cut from the aorta and vena cava of a cow or sheep.
The length of a ring of artery with a mass carrier attached to it is measured and regarded as the ‘original length’ for all calculations.
A 10g mass is added to the carrier and the new length is recorded and the percentage change in length (compared with original length) is recorded.
This is repeated using additional 10g masses up to 50g for an artery.
The same procedure repeated using a ring of vein.
A greater percentage change in length is obtained for arteries which shows that arteries contain more elastic fibres in their walls than veins.
Blood vessels - capillaries
Capillaries are the smallest blood vessels and have very thin walls.
As blood flows through a capillary fluid is forced through the walls by the blood pressure and enters the tissue space.
The capillaries are so narrow that red blood cells must squeeze through, this slows down the rate of blood flow and allows more time for exchange of substances between the blood and the cells.
5. Structure and functions of arteries, capillaries and veins
c) Exchange of materials
Pressure filtration causes plasma to pass through the capillary walls into the tissue fluid surrounding the cells.
Tissue fluid supplies cells with glucose, O2 and other substances. CO2 and other metabolic wastes diffuse out of the cells into the tissue fluid to be excreted.
Exchange of materials
Tissue fluid and plasma are similar composition but tissue fluid does not contain plasma proteins as they are too large to be filtered through the capillary wall.
Blood arriving in arteries is a higher pressure than blood in the capillaries
The capillary network so dense that every living cell is located close to a capillary and constantly bathed in tissue fluid.
Water moves from a HWC (tissue fluid lacking plasma proteins) to a LWC (plasma rich in proteins).
Excess tissue fluid is absorbed by lymphatic vessels and return it as lymph to the circulatory system.
Exchange of materials
Most tissue fluid returns to the blood.
Large vessels return lymph back to blood via two ducts at the subclavian veins
Lymph fluid passes through a series of lymph nodes which contain cells of the immune system.
The nodes act as filters, removing foreign particles from the lymph fluid.
Exchange of materials – lymphatic system
Excess tissue fluid is absorbed by lymphatic vessels and return it as lymph to the circulatory system.
6. Structure and function of the heart
a) Cardiac output and its calculation
STRUCTURE OF THE HEART
Aorta
Superior Vena cava
Right atrium
Atrioventricular (AV) valve
Bicuspid valve
Right ventricle
Inferior vena cava
Pulmonary arteries
Pulmonary veins
Left atrium
Atrioventricular (AV) valve
Tricuspid valve
Left ventricle
Septum
Structure of the heart
Use the word bank to label the structures of the heart
Add arrows to your diagram to show the direction of blood flow through the heart
Use a stethoscope to listen to your own heart sounds
The heart and its associated blood vessels
Jugular vein
Pulmonary artery
Vena cava
Hepatic vein
Hepatic portal vein
Renal vein
Coronary vein
Carotid artery
Pulmonary vein
Aorta
Coronary artery
Hepatic artery
Renal artery
Colour in the diagram and label the arteries and veins
Cardiac function
The left and right ventricles pump the same volume of blood through the pulmonary artery and the aorta during each contraction of the heart.
heart rate
The number of heartbeats per minute
stroke volume
The volume of blood expelled by each ventricle on contraction.
cardiac output
The volume of blood pumped through each ventricle per minute is the cardiac output.
CO = HR x SV
(cardiac (heart (stroke
output) rate) volume)
Cardiac output is determined by heart rate and stroke volume
State of body | Heart rate (beats/min) | Stroke volume (ml) | Cardiac output by each ventricle (l/min) |
At rest | 60 | 60 | 3.6 |
During exercise | 120 | 70 | 8.4 |
During strenuous exercise | 180 | 80 | 14.4 |
Cardiac function
The table shows the changes to cardiac output at three levels of activity.
In your exam you will be asked how to calculate a cardiac output from data your are given.
Make sure you learn the formula.
Cardiac function
5.76l/min
100 beats/min
100ml
120ml
6. Structure and function of the heart
b) The cardiac cycle
Cardiac cycle
The cycle is divided into;
The sequence of filling and emptying of the heart chambers is called the cardiac cycle.
On average the length of one cardiac cycle is 0.8secs based on a heart rate of 75bpm.
60
0.8 = 75 bpm
Opening and closing of the heart valves are responsible for the heart sounds that can be heard with a stethoscope.
Cardiac cycle
During diastole, the heart muscle relaxes and blood returning to atria flows into ventricles. Eventually, atrial pressure exceeds the pressure in the ventricles and the AV valves are pushed open allowing blood to enter the ventricles.
Atrial systole transfers the remaining blood through the already open AV valves to the relaxed ventricles.
Ventricular systole closes the AV valves. Blood is pumped out the ventricles through the semi-lunar valves into aorta and pulmonary arteries.
During diastole the higher pressure in the arteries closes the SL valves.
Cardiac cycle
Z – ventricular pressure falls below atrial pressure and the AV valve opens.
The graph refers to the left side of the heart only.
W – ventricular pressure exceeds atrial pressure forcing the AV valves to close (‘lubb’)
X – ventricular pressure exceeds aortic pressure forcing the semi lunar valves open
Y – ventricular pressure falls below aortic pressure causing the SL valves to close (‘dupp’)
W
X
Z
Y
Stages in the cardiac cycle
1. Atrial and ventricular diastole |
|
2. Atrial systole (ventricular diastole) |
|
3. Ventricular systole (atrial diastole) |
|
Summary of valves
Name of valve | Location | Phase of cardiac cycle when valve is closed | Function of valve |
Atrioventricular valves | Between atria and ventricles | Ventricular systole | Prevent backflow of blood into atria |
Semilunar valves | Start of pulmonary artery and the aorta | Atrial systole | Prevent backflow of blood from the main arteries into the ventricles |
6. Structure and function of the heart
c) The structure and function of the cardiac conducting system
The heartbeat originates in the heart. Heart muscle cells are able to contract on their own but the contraction of each heart chamber must be co-ordinated to allow the correct movement of blood.
Coordination of the cardiac cycle is brought about by the conducting system of the heart.
Cardiac conducting system
Cardiac conducting system
A cardiac impulse is initiated in the wall of the right atrium from a specialised bundle of cells called the sinoatrial node (the pacemaker). These cells are auto-rhythmic and control the timing of cardiac muscle cell contraction.
Impulses from SA node spread through the atria causing atrial systole.
These impulses travel to the atrioventricular node (AV node) located in the centre of the heart.
Impulses from AV node travel down conducting fibres in the central wall of the heart which divide into left and right branches.
Each branch is continuous with a network of tiny fibres in the ventricle walls and stimulation causes ventricular systole from the apex upwards to squeeze blood out of the ventricles.
Regulation of heart rate
The SA node co-ordinates each heartbeat but heartrate is not fixed and is altered by nervous and hormonal control.
Antagonistic = work on the same organ systems but have opposite effects on heart rate.
The medulla regulates the rate of SA node through the antagonistic action of the autonomic nervous system (ANS).
Nervous control
The rate the heart beats is determined by which system exerts the greater influence.
Parasympathetic nerve
(decreases heart rate)
Sympathetic nerve
(increases heart rate)
The autonomic nervous system is divided into two branches;
A sympathetic nerve releases noradrenaline which increases heart rate
A parasympathetic nerve releases acetylcholine which decreases heart rate.
Regulation of heart rate – nervous control
Regulation of heart rate – nervous control
Branch of autonomic nervous system | Chemical produced | Effect |
Sympathetic nervous system | Noradrenaline | Increases heart rate and cardiac output |
Parasympathetic nervous system | Acetylcholine | Decreases heart rate and cardiac output |
Hormonal control
Regulation of heart rate
Under certain circumstances such as ‘fight or flight’ the sympathetic nervous system acts on the adrenal glands, making them release adrenaline into the blood. When adrenaline reaches the SA node this hormone makes the pacemaker increase heart rate
Sympathetic nerve increases heart rate
Parasympathetic nerve decreases heart rate
Adrenaline
Increases heart rate
Electrocardiogram
Impulses in the heart generate currents that can be detected by an electrocardiogram - ECG.
A normal ECG consists of 3 distinct waves
P wave – atrial systole
QRS complex – ventricular systole
T wave - diastole
Atrial flutter - contractions occur more rapidly and not co-ordinated. More p-waves than QRS complexes
Ventricular Tachycardia - cells in ventricle walls beat rapidly and independently of the atria. P waves are absent and QRS complex is abnormal.
Ventricular fibrillation - contractions of different groups of heart muscles at different times. Impossible for co-ordinated contraction. Lethal if not corrected.
Abnormal ECGs
Calculation of heart rate
Calculate this heart rate
0.5 seconds
The length of this cardiac cycle =
Heart rate =
60
0.5 = 120 bpm
6. Structure and function of the heart
d) Blood pressure changes in aorta during cardiac cycle
Blood pressure
The force exerted by blood against the walls of the blood vessels. Measured in mmHg.
A typical blood pressure reading for a young adult is 120/80mmHg.
Measure your own blood pressure using a sphygmomanometer.
Systolic = contraction of heart
Diastolic = relaxation of the heart
Measuring blood pressure
Systolic and diastolic pressures can be measured using a sphygmomanometer.
The blood flows freely through the artery (when a pulse is not detected) at diastolic pressure.
Typical value = 120/80mmHg.
An inflatable cuff stops blood flow in the artery, and deflates gradually.
The blood starts to flow (detected by a pulse) at systolic pressure.
Decreasing blood pressure during circulation
As blood enters the narrower vessels there is friction between the blood and vessel wall. This resistances slows blood flow and reduces blood pressure.
Blood pressure increases during ventricular systole and decreases during diastole.
In the arteries, the walls bulge during systole as a wave of blood passes through, and recoil during diastole.
There is a progressive decrease in pressure as blood travels around the circulatory system, dropping to almost zero by the time it reaches the right atrium again.
Commonly found in people with an unhealthy lifestyle
A major risk factor for many diseases including coronary heart disease.
High blood pressure - prolonged elevation of blood pressure at rest.
Indicated by systolic values >140mmHg and diastolic values >90mmHg.
Hypertension
a) Process of atherosclerosis
7. Pathology of cardiovascular disease
Atherosclerosis
Accumulation of fatty material (consisting mainly of cholesterol, fibrous material and calcium) forming an atheroma or plaque beneath the endothelium.
As the atheroma grows;
Symptoms of atherosclerosis normally remain absent until later life and it is the root cause of various cardiovascular diseases (CVD) - angina, stroke, heart attack and peripheral vascular disease.
b) Thrombosis
7. Pathology of cardiovascular disease
Thrombosis
Blood clotting is a protective device triggered by damage to cells to prevent blood loss from a wound
The damage releases clotting factors that activate a cascade of reactions…………….
Atheromas can rupture and damage the endothelium.
Thrombosis
Atheroma ruptures and damages the endothelium
The damage releases clotting factors
Clotting factors activate a cascade of reactions resulting in the conversion of the enzyme prothrombin into its active form thrombin
Thrombin causes the plasma protein fibrinogen to form threads of fibrin
The fibrin threads form a meshwork to seal the wound and provide a scaffold for the formation of scar tissue.
Creates a meshwork to seal the wound and a scaffold for the formation of scar tissue
Release of Clotting factors
Thrombin
(active enzyme)
Fibrin
(insoluble)
Fibrinogen
(soluble)
Thrombin causes fibrinogen (plasma protein) to form threads of fibrin.
Clotting factors cause the conversion of the enzyme prothrombin to its active form thrombin.
Peter
Couldn’t
Throw
For
Fudge
Thrombosis
Atheroma damages the endothelium
Prothrombin
(inactive enzyme)
Thrombosis – MI
A thrombosis in a coronary artery can lead to a myocardial infarction (MI), commonly known as a heart attack.
In some cases a thrombus may break loose, forming an embolus which travels through the blood until it blocks a blood vessel.
Blood clot = thrombus
The process of forming a blood clot = thrombosis.
Cells are deprived of oxygen leading to death of the tissues.
Restriction or blockage of this blood supply can cause angina. Crushing chest pain, radiating down the left arm and up to the neck and jaw.
Thrombosis – stroke
A thrombosis in an artery in the brain can lead to a stroke.
The surrounding cells are deprived of oxygen leading to death of the tissues.
Blood clot = thrombus
The process of forming a blood clot = thrombosis.
c) Causes and effects of peripheral vascular disorders
7. Pathology of cardiovascular disease
Peripheral vascular disease
Narrowing of the arteries (due to atherosclerosis) other than those of the heart or brain.
The arteries of the legs are most commonly affected. Pain is experienced in the leg muscles due to a limited supply of oxygen
A deep vein thrombosis (DVT) is a blood clot that forms in a deep vein, most commonly in the lower leg. This causes the affected area to swell and become painful.
Pulmonary embolism
If a thrombus from a leg vein breaks free it can result in a pulmonary embolism in the lungs.
This is characterised by chest pain, shortness of breath and palpitations.
Treatment is in the form of anticoagulant drugs such as heparin.
If left untreated can cause collapse and potentially death.
Match the terms in column A to the definition in column B
Column A | Column B |
1. Atheroma | (a) Blood clot that has broken free and lodged in a blood vessel in the lung |
2. Fibrin | (b) Caused by blockage of the coronary artery |
3. Stroke | (c) Enzyme that converts fibrinogen to fibrin |
4. DVT | (d) Blood protein that is converted to fibrin during blood clotting |
5. Myocardial infarction | (e) Caused by formation of a blood clot in the deep veins of the leg |
6. Pulmonary embolus | (f) Insoluble fibres which form a mesh during scar-tissue formation |
7. Thrombin | (g) Plaque composed of fibrous and fatty material which forms under the endothelium |
8. Fibrinogen | (h) Paralysis caused by a blockage of blood vessels in the brain |
1 – g 4 – e 7 - c
2 – f 5 – b 8 - d
3 – h 6 - a
d) Control of cholesterol levels in the body
7. Pathology of cardiovascular disease
Cholesterol
Cholesterol is a type of lipid found in the cell membrane.
Cholesterol is synthesised by all cells, but 25% of total production takes place in the liver.
A diet high in saturated fats or cholesterol causes an increase in cholesterol levels in blood.
It is also used to make the sex hormones – testosterone, oestrogen and progesterone.
Transport of cholesterol
Lipoproteins are molecules of lipid and protein found in plasma which transport cholesterol.
Transport cholesterol to the body cells.
High density lipoprotein (HDL)
Transports excess cholesterol from body cells back to the liver for elimination. This helps to prevent cholesterol accumulating in blood.
Low density lipoprotein (LDL)
LDL
HDL
Most cells have LDL receptors in their membranes. These attach to LDL and engulf it into the cell where it releases cholesterol.
Once a cell has sufficient cholesterol, negative feedback inhibits the synthesis of new LDL receptors and LDL circulates in the blood where it may deposit cholesterol in the arteries forming atheromas.
Cholesterol
Blood
Blood from liver
LDL cholesterol
LDL cholesterol engulfed by body cells
Body cells
Enlarged
Excess LDL cholesterol
Atheroma
Ratios of HDL to LDL
A higher ratio of HDL to LDL will result in lower blood cholesterol and a reduced chance of atherosclerosis
Dietary changes such as reducing the levels of total fat in the diet and replacing saturated fats with unsaturated fats will also contribute to lower cholesterol
Regular physical activity tends to raise HDL levels and so lowers blood cholesterol.
Reducing cholesterol with statins
If altering diet and taking exercise do not reduce cholesterol levels, drugs such as statins can be prescribed.
Statins reduce blood cholesterol by inhibiting an enzyme essential for the synthesis of cholesterol by liver cells.
As less cholesterol is manufactured in the liver there is a decrease in blood cholesterol level.
Statins also increase the number of LDL receptors to cause a reduction in the level of LDL cholesterol from the blood.
Cholesterol synthesis
Statins
X
a) Chronic elevated blood glucose levels lead to atherosclerosis and blood vessel damage
8. Blood glucose levels and obesity
Blood glucose levels and vascular disease
Chronic elevation of blood glucose levels leads to endothelium cells taking in more glucose than normal, damaging the blood vessels. Atherosclerosis may develop leading to peripheral vascular disease, cardiovascular disease or stroke.
Endothelial cells lining arterioles become thicker and weaker. Walls lose their strength and may burst and bleed into surrounding tissues, reducing blood flow through body.
Small blood vessels damaged by elevated blood glucose levels may result in haemorrhage of blood vessels in the retina, renal failure or peripheral nerve dysfunction.
Blood glucose levels and vascular disease
Diabetic retinopathy from prolonged high blood glucose levels causes small vessels in the eye to haemorrhage. Left untreated this can cause blindness.
Blood glucose levels and vascular disease
Retina
Damage to arterioles can cause renal failure as kidneys are no longer able to effectively filter and purify blood leading to
- shortness of breath on exertion
Blood glucose levels and vascular disease
Kidneys
Peripheral nerves
Peripheral neuropathy - nerves are damaged due to prolonged exposure to high glucose levels and can take the form of numbness, tingling or pain in the hands, arms, toes and feet. If left untreated this can lead to development of ulcers and eventually amputation.
Blood glucose levels and vascular disease
8. Blood glucose levels and obesity
b) Control of blood glucose
All living cells need a supply of glucose for respiration. Blood glucose levels are maintained at a constant level through negative feedback control.
This promotes storage of glucose in the liver when there is an excess in the blood and stimulates the release of glucose by the liver into the blood as body cells use it up.
This regulation is brought about by pancreatic hormones insulin and glucagon.
Regulation of blood glucose levels
Regulation of blood glucose levels
liver
liver
Receptor cells in pancreas
Receptor cells in pancreas
Normal glucose concentration in blood
Normal glucose concentration in blood
Conversion of glucose to glycogen
About 100g of glucose are stored as glycogen in the liver.
Insulin and glucagon act antagonistically.
Increase in blood glucose concentration
Increased secretion of insulin
(less glucagon)
Decrease in blood glucose concentration
Decrease in blood glucose
Increased secretion of glucagon
(less insulin)
Glycogen converted to glucose
Increasing blood glucose concentration
Pancreatic receptors respond to raised blood glucose levels
Regulation of blood glucose levels
Pancreatic receptors increase secretion of insulin
Insulin activates the conversion of glucose to glycogen in the liver
Decrease in blood sugar levels
Pancreatic receptors respond to lowered blood glucose levels
Pancreatic receptors increase secretion of glucagon
Glucagon activates the conversion of glycogen into glucose in the liver
Increase in blood sugar levels
During exercise and 'fight or flight' responses glucose concentrations in the blood are raised by adrenaline released from the adrenal glands.
Regulation of blood glucose levels - Adrenaline
Adrenaline overrides normal blood glucose control by stimulating glucagon secretion and inhibiting insulin secretion.
c) Type 1 and type 2 diabetes
8. Blood glucose levels and obesity
Diabetes
People who suffer from diabetes are unable to control their blood glucose level.
If left untreated blood glucose levels can rise to
10-30mmol/l compared with normal blood glucose levels of around 5mmol/l
There are two types of diabetes:
Type 1 diabetes
Usually occurs in childhood.
The pancreas is unable to produce insulin.
Treated by regular injections of insulin.
Type 2 diabetes
Treated by diet control, exercise and weight loss.
Typically develops later in life.
The likelihood of developing type 2 diabetes is increased by being overweight or obese.
The kidneys will remove some of this glucose but the kidney filtrate is so rich in glucose but not all of it is absorbed back into blood and therefore excreted in urine.
Testing urine for glucose is often used as an indicator of diabetes.
In both types of diabetes, individual blood glucose concentrations will rise rapidly after a meal.
Diabetes diagnosis
A clinical test used to diagnose diabetes.
Blood glucose concentrations of an individual are measure after fasting.
They consume a known mass of glucose and changes in their blood glucose concentration is monitored for at least the next 2 hours.
The results plotted to give a glucose tolerance curve
Glucose tolerance test
3. Diabetic
2. Mild diabetic - diet controlled.
d) Obesity
8. Blood glucose levels and obesity
Obesity
Characterised by accumulation of excess body fat in relation to lean body tissue such as muscle.
Obesity is a major risk factor for cardiovascular disease and type 2 diabetes and may impair health
Most common cause is excessive consumption of food rich in fats and free sugars combined with lack of physical activity.
Methods of measuring body composition
BMI greater than 30 is used to indicate obesity
Body mass index (BMI) is commonly used to measure obesity
body mass (kg)
BMI =
height (m2)
BMI range | Category |
<18.5 | Underweight |
18.5-24.9 | Normal |
25-29.9 | Overweight |
>30 | Obese |
Calculating BMI can also wrongly classify muscular individuals as obese e.g. body builders who have allow percentage of body fat and an unusually high percentage of muscle bulk.
Methods of measuring body composition
Methods of measuring body composition
The table below shows the height and mass of four individuals.
Individual | Height (cm) | Mass (kg) |
Untrained male | 170 | 65.0 |
Male athlete | 180 | 105.0 |
Untrained female | 168 | 82.4 |
Female athlete | 177 | 91.5 |
Answers |
22.5 |
32.4 |
29.2 |
29.2 |
The trained female has a greater mass of muscle than the untrained female.
The role of diet and exercise in reducing obesity and CVD
The energy intake in the diet should limit fats and free sugars.
Fats have a high calorific value per gram
Free sugars require no metabolic energy
to be expended in their digestion.
Obesity is linked to high fat diet and a decrease in physical activity
Risk factors of CVD
High LDL-cholesterol
Consuming a diet high in saturated fat
Physical inactivity
A stressful lifestyle
Obesity
Physical inactivity
Hypertension
Smoking
Diabetes
Consuming excess alcohol
Exercise increases energy expenditure and preserves lean tissue.
The role of diet and exercise in reducing obesity and CVD
Exercise can help to reduce risk factors for cardiovascular disease (CVD) by: