Topic 6: Human health and physiology
6.1 Digestion
6.1.1 Explain why digestion of large food molecules is essential.
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Large food molecules are usually polymers, such as polysaccharides, proteins and lipids,
which are too large to be absorbed from the digestive tract into the circulatory system for
transport because they are simply too large to move across the membranes of small
intestine epithelial cells.
After digestion, polysaccharides are broken down into monosaccharides, polypeptides
are broken down into amino acids, and lipids are broken down into glycerol and fatty
acids.
Monomers, such as monosaccharides, amino acids, glycerol, and fatty acids are small
enough to be absorbed by small intestine epithelial cells, moving these substances by
diffusion, facilitated diffusion, or active transport through membrane proteins.
6.1.2 Explain the need for enzymes in digestion. The need for increasing
the rate of digestion at body temperature should be emphasized.
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At body temperature (37°C in mammals), reaction rates are too slow to be efficient at
hydrolysis reactions of large food molecules
Hydrolytic reactions in the digestion of large food molecules, such as polysaccharides,
proteins and lipids into their monomers, are exothermic, but occur very slowly due to
considerable activation energy
Enzymes lower activation energy, catalyzing hydrolysis reactions of large food molecules
into their monomers
6.1.3 State the source, substrate, products and optimum pH conditions for
one amylase, one protease and one lipase. Any human enzymes can be
selected. Details of structure or mechanisms of action are not required.
Enzyme
Salivary amylase
Pepsin
Pancreatic lipase
Source
salivary glands
stomach
pancreas
Substrate
starch
proteins
Products
maltose
polypeptides
Optimum pH
7-8
1.5-2.5
Triglycerides (fats
and oils)
fatty acids and
glycerol
7
6.1.4 Draw and label a diagram of the digestive system. The diagram should
show the mouth, esophagus, stomach, small intestine, large intestine, anus,
liver, pancreas and gall bladder. The diagram should clearly show the
interconnections between these structures.
6.1.5 Outline the function of the stomach, small intestine and large intestine.
Stomach:
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A large, expandable, muscular and glandular organ
Stores and mixes food, aiding in both physical and chemical digestion
gastric pits secrete:
a) HCl, producing a stomach pH of about 2, facilitating pepsin activity, and killing foreign
pathogens, such as bacteria
b) pepsinogen, an inactive precursor which is converted to pepsin under acidic conditions
c) pepsin catalyzes the hydrolysis of large proteins and polypeptides into smaller polypeptides
d) mucus, which protects stomach cells from acidic conditions
e) chyme = product of stomach digestion, an acid fluid released from stomach into small intestine
via pyloric sphincter
Small intestine:
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Digestion:
a) pancreas releases bicarbonate = NaHCO3b) which neutralizes acidic chyme, producing a pH = 8, optimizing activities of intestinal enzymes
c) enzymes from pancreas, and small intestine epithelial cells hydrolyze large molecules into
smaller molecules
d) polypeptides digested into amino acids
e) polysaccharides & disaccharides digested into monosaccharides
f) triglycerides digested into fatty acids and glycerol
g) bile produced in liver, stored in gall bladder, released through pancreatic duct
h) emulsifying fat droplets into smaller particles on which pancreatic lipase can act more
efficiently
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motility by peristalsis: rhythmic contractions of circular and longitudinal smooth muscles
lining small intestine slowly force chyme down intestinal tract
absorption: lining of small intestine is folded, increasing surface area for absorption, and
each fold is folded again into villi, with each villus acting an absorptive unit
Large intestine:
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absorption of vitamin K produced by mutualistic bacteria
reabsorption of water, Na+, K+ from intestinal lumen to capillaries
motility by peristalsis: rhythmic contractions of circular and longitudinal smooth muscles
lining large intestine slowly force fecal matter down intestinal tract
6.1.6 Distinguish between absorption and assimilation.
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absorption: movement of chemical substances from the lumen of the digestive tract
across the membranes of cells lining the digestive tract by diffusion, facilitated diffusion,
or active transport, and then either into the circulatory or lymphatic systems for
distribution to all somatic cells
assimilation: following digestion and absorption, nutrients are taken into somatic cells and
converted to the biomass of the organism
6.1.7 Explain how the structure of the villus is related to its role in
absorption and transport of the products of digestion.
A. surface area:
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Folding: intestinal folding increases surface area by 3X;
Villi: within each fold, a second set of folds creates a series of villi, with each villus being
a finger-like projection, increasing intestinal surface area by an additional 10X;
Microvilli: along the lumen side of each small intestine epithelial cell a brush border of
microvilli additionally expands surface area by another 20X;
Thus, the total surface area increase = 3 x 10 x 20 = 600x
B. Membranes of epithelial cells:
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diffusion of fatty acids, monoglycerides, fat-soluble vitamins, some mineral ions through
membrane phospholipid bilayer
facilitated diffusion of some monosaccharides, some vitamins and mineral ions using
membrane proteins
active transport of amino acids, most monosaccharides, some mineral ions, using
membrane proteins & ATP produced by mitochondria in epithelial cells
C. Blood capillaries:
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oxygenated blood enters villus supplying oxygen for cellular respiration:
cell growth replacing lost/injured cells
ATP for active transport
deoxygenated blood leaves villus rich in absorbed nutrients: amino acids,
monosaccharides, mineral ions, vitamins
D. Lacteals = branches of lymphatic system:
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fatty acids and glycerol are reformed into triglycerides in epithelial cell smooth ER/Golgi
apparatus
triglycerides, with phospholipids and cholesterol, aggregate into chylomicrons which are
coated with proteins and then leave epithelial cells and enter lacteals
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6.2 The transport system
6.2.1 Draw and label a diagram of the heart showing the four chambers,
associated blood vessels, valves and the route of blood through the heart.
Care should be taken to show the relative wall thickness of the four
chambers. Neither the coronary vessels nor the conductive system are
required.
6.2.2 State that the coronary arteries supply heart muscle with oxygen and
nutrients.
6.2.3 Explain the action of the heart in terms of collecting blood, pumping
blood, and opening and closing of valves. A basic understanding is
required, limited to the collection of blood by the atria, which is then
pumped out by the ventricles into the arteries. The direction of flow is
controlled by atrio-ventricular and semilunar valves.
Collecting of blood:
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deoxygenated blood enters the right atrium from the inferior and superior vena cava
oxygenated blood enters the left atrium from the pulmonary vein
Pumping of blood:
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contraction of the atria (right and left) pumps the blood into the ventricles (right and left)
contraction of ventricles (right and left) pumps the blood into the pulmonary artery(right)
and aorta (left)
Opening and closing of valves:
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as a function of pressure differences, one-way valves prevent backflow of blood
atrioventricular valves prevent backflow from ventricles into atria
semilunar valves prevent backflow of blood from pulmonary artery into right ventricle and
from aorta into left ventricle
6.2.4 Outline the control of the heartbeat in terms of myogenic muscle
contraction, the role of the pacemaker, nerves, the medulla of the brain and
epinephrine (adrenaline). Histology of the heart muscle, names of nerves or
transmitter substances are not required.
A. Heart beat: electrical impulses cause regular contractions of, first the two atria, and then the
two ventricles
B. Myogenic nature:
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the sino-atrial node (SAN), known as the pacemaker, is a specialized set of cells located
on the right atrium
SAN, not the brain, generates regular electrical impulses autonomously
SAN impulses spread throughout both atria, causing simultaneous contraction
impulse spread to ventricles only at the atrio-ventricular node (AVN) with a delay of about
0.1 seconds
AVN transmits electrical signals to heart apex via bundles of His
signals trigger powerful contractions of both ventricles from the apex toward the atria
bundle of His transmits electrical signals throughout ventricles via Purkinje fibers, causing
simultaneous contraction of ventricles
C. Nerve stimulation:
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sympathetic nerves from brain increase heart rate
parasympathetic nerves from brain via vagus nerve decrease heart rate
D. Hormone stimulation:
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adrenaline (epinephrine) from adrenal medulla increase heart rate
Myogenic Rhythm can be modified by the central nervous
system to respond to cardio-vascular demands. Within
the medulla region of the brain there are a specialised
group of receptors and co-ordinators called the Cardiac
Centre. These are connected to the the SAN via the two
sets of nerves.
a) Accelerator nerve that increases the rate SAN activity
to produce faster heart rate.
b) Decelerator nerve that decreases the rate SAN activity
to slow heart rate.
In addition the SAN is sensitive to hormones such as
adrenaline that can directly stimulate heart rate.
The brain is sensitive to a wide range of stimuli including
pH and CO2 levels which reflect the demand of the
tissues for oxygen. As an example, exercise produces
more CO2 in the plasma. Detected by the cardiac centre
this stimulates the accelerator nerve and therefore the
SAN to increase heart rate. i.e. your heart beats faster
when you exercise.
6.2.5 Explain the relationship between the structure and function of arteries,
capillaries and veins.
vessel
artery
structure
function
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Thick outer layer of collagen and
elastic fibres
Thick wall
Thick layers of elastic and muscle
fibres
Narrow lumen
Thin outer layer of collagen and
elastic fibres
Thin wall
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To avoid bulges and leaks
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To withstand high pressures
To help pump the blood after each
heart beat
To maintain high pressures
Little danger of bursting
Thin layers of elastic and muscle
fibres
Wide lumen
Valves
Wall consists of a single layer of
thin cells surrounded by
basement membrane
Very narrow lumen
Pores between cells in the wall
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vein
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capillary
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Allows vein to be pressed by adjacent
muscles
Blood does not flow in pulses, so vein
walls cannot help it
To accommodate slow flowing blood
Prevent backflow of blood
Small distance for diffusion of
dissolved materials between blood &
tissues
Capillaries fit into small spaces
Allow some of plasma to leak out and
form tissue fluid
6.2.6 State that blood is composed of plasma, erythrocytes, leucocytes
(phagocytes and lymphocytes) and platelets.
6.2.7 State that the following are transported by the blood: nutrients,
oxygen, carbon dioxide, hormones, antibodies, urea and heat.
6.3 Defence against infectious disease
6.3.1 Define pathogen.
Pathogen: an organism or virus that causes a disease.
6.3.2 Explain why antibiotics are effective against bacteria but not against
viruses.
Antibiotics block specific metabolic pathways found in bacteria. Viruses reproduce using the host
cell’s metabolic pathways, which are not affected by antibiotics.
6.3.3 Outline the role of skin and mucous membranes in defence against
pathogens.
 1st line of defense = nonspecific
 skin: tightly bound barrier of dead, keratin-rich epidermal cells
1. tough, elastic, waterproof surface
2. sebum: oily secretions from sebaceous gland in hair follicles, preventing skin cracking
3. inhibiting growth of pathogens
 mucous membranes: linings of intestinal tract, respiratory tract, eyes, genitals
1. mucous traps microbes
2. lysozymes: antibacterial enzymes
3. cilia: clear respiratory tract
4. acidity: stomach: pH = 2; vagina pH = 5-6
6.3.4 Outline how phagocytic leucocytes ingest pathogens in the blood and
in body tissues.
 damage to tissues allows invasion across 1st line of defense
 microbes successfully invade body fluids or tissues
 damaged cells release histamine and other chemicals initiating inflammation
 phagocytes attracted to site by chemotaxis toward histamine
 phagocytes recognize microbes as foreign by antigen recognition
 phagocytes endocytotically engulf microbes in phagosomes, which are digested by
enzymes held in lysosomes
 digested microbe fragments are displayed on cell membrane
 phagocytes with microbe fragments displayed = antigen-presenting cells: APCs
6.3.5 Distinguish between antigens and antibodies.
 antigen: a molecule recognized as foreign by the immune system; it elicits an immune
response
 antibody: (=immunoglobulin) a globular protein that recognizes an antigen by its
complementary shape and charge, thus allowing it to attach to the antigen specifically,
marking it for attack by the immune system
6.3.6 Explain antibody production. Many different types of lymphocyte exist.
Each type recognizes one specific antigen and responds by dividing to
form a clone. This clone then secretes a specific antibody against the
antigen.
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macrophages, following phagocytotic digestion, display antigen on surface, becoming
antigen-presenting cells = APCs
macrophages activate only helper T-lymphocytes with receptor proteins specifically
matching the antigen of the APCs
only those B-lymphocytes with antibodies specifically matching helper T-lymphocytes
receptor proteins are activated
clonal selection of activated B-lymphocytes produces a large population of B-lymphocyte
plasma cells and memory cells
B-lymphocyte plasma cells produce massive quantities of antibodies (1000s/sec) during
protein synthesis, releasing them by exocytosis into the surrounding humors = blood,
tissue fluids, and lymph
antibodies adhere to antigens, marking them for phagocytosis by macrophages
memory B-lymphocytes & helper T-lymphocytes specific to the pathogen remain in the
lymph nodes in elevated quantities, and upon subsequent exposure to the antigen,
produce a rapid and intense response = secondary response
6.3.7 Outline the effects of HIV on the immune system. The effects of HIV should
be limited to a reduction in the number of active lymphocytes and a loss of the
ability to produce antibodies.
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reduction in the number of active lymphocytes
loss of the ability to produce antibodies
6.3.8 Discuss the cause, transmission and social implications of AIDS.
6.4 Gas exchange
6.4.1 Distinguish between ventilation, gas exchange and cell respiration.
VENTILATION = breathing, or the bulk movement of air into and out of the lungs, by:
 inhalation, which occurs when muscular contractions increase
the volume of the lungs thus decreasing the pressure so air
enters the lungs,
 exhalation, when muscular relaxation decreases the volume of
the lungs thus increasing pressure so gases exit the lungs
GAS EXCHANGE = the process whereby O2 is acquired and CO2 is removed between respiring
cells and the environment; the gas exchange surface = alveoli
CELL RESPIRATION = breakdown of glucose and other molecules in the mitochondria of cells
creating a constant demand for O2 and a need to eliminate CO2
Click to view an animation showing gas exchange:
http://www.airinfonow.org/html/lungattack/lungplay.htm
6.4.2 Explain the need for a ventilation system. A ventilation system is needed to
maintain high concentration gradients in the alveoli.
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adequate lung ventilation is essential to gas exchange which is turn essential to cell
respiration and the energy needs of cells, tissues, organs and organisms
ventilation provides a continual supply of fresh air to the lungs and helps to maintain a
large diffusion gradient for respiratory gases across the gas exchange surface of the
alveoli
O2 must be delivered regularly to supply the needs of respiring cells
CO2 must be quickly eliminated from the body to reduce its toxic effects
6.4.3 Describe the features of alveoli that adapt them to gas exchange. This
should include a large total surface area, a wall consisting of a single layer of
flattened cells, a film of moisture and a dense network of capillaries.
Alveoli = the millions of thin-walled, dead-ends of the bronchioles forming clusters of air sacs
acting as the respiratory surface with features of:
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large surface area: surface area of the alveolar epithelium - 100 m2
thin: single cell layer of epithelium across which diffusion occurs
moist: gasses need to dissolve before passing membranes
rich blood supply: extensive net of capillaries for transport of gasses to and from alveoli
Click to view an animation showing gas exchange: http://highered.mcgrawhill.com/sites/0072437316/student_view0/chapter44/animations.html#
6.4.4 Draw and label a diagram of the ventilation system, including trachea, lungs,
bronchi, bronchioles and alveoli. Students should draw the alveoli in an inset
diagram at a higher magnification.
6.4.5 Explain the mechanism of ventilation of the lungs in terms of volume and
pressure changes caused by the internal and external intercostals muscles, the
diaphragm and abdominal muscles.
6.5 Nerves, hormones and homeostasis
6.5.1 State that the nervous system consists of the central nervous system (CNS)
and peripheral nerves, and is composed of cells called neurons that can carry
rapid electrical impulses.
The nervous system is divided into two main parts:
1. The central nervous system (CNS) is made of the brain and the spinal cord. The
brain is enclosed inside the skull and the spinal cord is enclosed inside the vertebral
column for protection.
2. The peripheral nervous system (PNS) is made of nerves that branch from the CNS.
The cranial nerves branch from the brain and supply areas in the head such as the
eyes, the facial muscles, the ears, and the nose.
The CNS functions mostly in gathering sensory information from nerves of the PNS,
processing this information, and then transmitting signals, again by the nerves of the PNS, to
effectors, or target organs or tissues, to react to this sensory input.
6.5.2 Draw and label a diagram of the structure of a motor neuron. Include dendrites, cell
body with nucleus, axon, myelin sheath, nodes of Ranvier and motor end plates.
6.5.3 State that nerve impulses are conducted from receptors to the CNS by sensory
neurons, within the CNS by relay neurons, and from the CNS to effectors by motor
neurons.
6.5.4 Define resting potential and action potential (depolarization and repolarization).
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The membrane potential of an excitable cell in a resting (unexcited) state is called
resting potential. Cells can change their membrane potential in response to
stimuli that can be received via gated ion channels.
Stimuli can cause an electrical gradient to be conducted across the membrane,
called hyperpolarization. Depolarization is a reduction in the electricial gradient
across the membrane. In an excitable cell, such as a neuron, the response to a
depolarizing stimulus is graded with stimulus intensity only up to a particular
level of depolarization, called the threshold position. If a depolarization reaches
the threshold, a different type of response called an action potential is triggered. It
is important to note, however, that hyperpolarizing stimuli do not produce action
potentials, but make it even more likely that an action potential will be triggered
by making it more difficult for a depolarizing stimulus to reach threshold.
The action potential, then, is the actual nerve impulse the cell transmits. The
magnitude of the action potential is independent of the strength of depolarizing
stimuli that triggers it. This whole sequence of events occurs in mere milliseconds.
Repolarization is when the membrane potential returns from
6.5.5 Explain how a nerve impulse passes along a non-myelinated neuron.
Include the movement of Na+ and K+ ions to create a resting potential and an
action potential.
The action potential takes place in the spot where the nerve is stimulated by a signal
generated and transmitted from another axon cell in the sequence. Then it starts travelling
in a wave form along the length of the axon until it reaches the opposite ends of the nerve
endings. The travelling action is called a nerve impulse. When it reaches the end of the
cell, the impulse enters another nerve cell in the sequence.
6.5.6 Explain the principles of synaptic transmission. Include the release,
diffusion and binding of the neurotransmitter, initiation of an action potential in
the post-synaptic membrane, and subsequent removal of the neurotransmitter.
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When the nerve impulse reaches the nerve endings it causes the presynaptic
membrane to become more permeable to calcium.
Calcium ions enter the presynaptic cell and causes the synaptic vesicles to move
to the cell membranes and burst open. This is a form of exocytosis and the
substance released from these vesicles is called a neurotransmitter.
The neurotransmitter is released into the synaptic cleft and it binds with the
receptor son the post synaptic membrane.
This combination of the transmitter and the receptors causes the membrane to
become more permeable to sodium.
Sodium ions enter causing depolarization followed by an action potential. The
action potential starts travelling from the dendrites to the cell body, to the axon to
the nerve endings.
The action of the neurotransmitter is terminated by the action of enzymes which
break it down into other substances.
These substances are then reabsorbed into the presynaptic membranes to be
assembled again into neurotransmitters.
The area that includes the presynaptic membrane, the synaptic cleft, and the
postsynaptic membrane is called a synapse.
6.5.7 State that the endocrine system consists of glands that release hormones
that are transported in the blood.
6.5.8 State that homeostasis involves maintaining the internal environment
between limits, including blood pH, carbon dioxide concentration, blood glucose
concentration, body temperature and water balance. The internal environment
consists of blood and tissue fluid.
6.5.9 Explain that homeostasis involves monitoring levels of variables and
correcting changes in levels by negative feedback mechanisms.
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set-point: a constant value to which a variable is constrained, such that any time the
variable fluctuates outside a given set-point range, negative feedback takes actions to
return the variable to its set-point
sensors: sensors respond to stimuli, gathering information about a variable in question,
signaling when its value fluctuates from the set-point
control center: receives information from sensors, comparing the value to a set-point,
and if necessary, directing actions to return the variable to its set-point
effectors: a mechanism for taking action to return a variable to its set-point, switching
on or off under the direction of the control center
responses: the resulting action produced by an effector, returning a variable to its setpoint value
6.5.10 Explain the control of body temperature, including the transfer of heat in
blood, and the roles of the hypothalamus, sweat glands, skin arterioles and
shivering.
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set-point: core body temperature = 37°C
SENSORS FOR TEMPERATURE:
a. hypothalamus is sensitive to blood temperature
b. skin warmth receptors
c. skin cold receptors
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CONTROL CENTER:
a. hypothalamus thermostat
b. cerebral cortex
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EFFECTORS:
IF Temperature is > 37°C
1) involuntary responses by sympathetic nervous system
a) vasodilation => increases heat loss
b) decreased basal metabolic rate => decreases heat production
c) sweating => increases heat loss
d) lethargy => decreases heat production
2) voluntary responses directed by cerebral cortex
a) rest => decreases heat production
b) behavioral responses (fanning, change to cooler clothing, cool drink)
IF Temperature is < 37°C
1) involuntary responses by sympathetic nervous system
a) vasoconstriction => decreases heat loss
b) increased basal metabolic rate => increases heat production
c) shivering => increases heat production
d) piloerection (goose bumps) => decreases heat loss
2) voluntary responses directed by cerebral cortex
a) rest => decreases heat loss
b) behavioral responses (muscular activity, change to warmer clothing, warm
drink, curling up, eating)
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RESPONSE:
IF Temperature is < 37°C effectors:
1) increase heat production,
2) decrease heat loss
3) until T = 37°C
IF Temperature is > 37°C effectors:
1) decrease heat production,
2) increase heat loss
3) until T = 37°C
6.5.11 Explain the control of blood glucose concentration, including the roles of glucagon,
insulin and α and β cells in the pancreatic islets.
Levels of blood glucose
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set-point: blood glucose = 90 mg/100 ml
sensors: stimulus = blood glucose levels above and below 90 mg/100 ml
Glucose detectors in pancreas islet beta cells detect high glucose levels
Glucose detectors in pancreas islet alpha cells detect low glucose levels
Control center:
a. pancreas islet beta cells
b. pancreas islet alpha cells
Effectors:
a. if blood glucose > 90 mg/100 ml, then pancreas beta cells produce and release insulin
b. if blood glucose < 90 mg/100 ml, then pancreas alpha cells produce and release
glucagon
Response:
If blood glucose > 90 mg/100 ml
1) insulin binds to receptors in muscle and liver cell membranes
2) moving glucose from the blood into liver and muscle cells
3) where glucose is either metabolized or stored as glycogen or fatty acids
4) in fat cells, insulin promotes glucose entry where it is converted to triglycerides
5) until blood glucose = 90 mg/100 ml
If blood glucose < 90 mg/100 ml
1) glucagon binds to receptors in liver cell membranes
2) which activates a cascade of enzymes which degrade glycogen into glucose
3) glucose moves from the liver into the blood
4) until blood glucose = 90 mg/100 ml
6.5.12 Distinguish between type I and type II diabetes.
Click to view an interactive tutorial about diabetes: http://www.diabetes.org/type-1-diabetes/wellbeing/LinkForLifeAd/link_for_life/main.html
6.6 Reproduction
6.6.1 Draw and label diagrams of the adult male and female reproductive systems.
The relative positions of the organs is important. Do not include any histological
details, but include the bladder and urethra.
The male reproductive system
The female rep roductive s ys tem
The female reproductive system
6.6.2 Outline the role of hormones in the menstrual cycle, including FSH (follicle
stimulating hormone), LH (luteinizing hormone), estrogen and progesterone.
FSH:
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released by anterior pituitary
promotes oogenesis in primary follicle in ovary
Estrogen:
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promotes secondary sexual characteristics:
o breast development
o pubic hair
o fatty deposits developing rounder hips
o female behavior pattern
inhibits milk production by mammary glands
increases thickness of endometrium of uterus
inhibits FSH production in anterior pituitary
stimulates LH production in anterior pituitary
LH:
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released by anterior pituitary in response to increasing estrogen levels
stimulates ovulation:
o release of secondary oocyte into oviduct
o follicle remains in ovary and matures into corpus luteum
Progesterone:
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inhibits milk production by mammary glands
increases/maintains thickness of endometrium of uterus
inhibits FSH production in anterior pituitary
inhibits LH production in anterior pituitary
6.6.3 Annotate a graph showing hormone levels in the menstrual cycle, illustrating
the relationship between changes in hormone levels and ovulation, menstruation
and thickening of the endometrium.
6.6.4 List three roles of testosterone in males. Limit this to pre-natal development
of male genitalia, development of secondary sexual characteristics and
maintenance of sex drive.
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pre-natal development of male genetalia
promotes development of sexual characteristics:
o primary:
 development of genitalia, ducts, glands
 spermatogenesis
o secondary:
 larynx growth
 facial, body, and pubic hair
 muscle and bone development
 male behavior pattern
maintenance of sex drive
6.6.5 Outline the process of in vitro fertilization (IVF).
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hormone injections into female cause more than one follicle to mature
secondary oocytes harvested from follicles at ovulation, via suction into syringe
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sperm donated from male mixed with eggs in petri dish, or injected directly into egg
development to blastocyst stage in petri dish
several embryos (up to 4) placed in uterus
if implantation is successful, one or more embryos will develop
additional embryos frozen for future use
6.6.6 Discuss the ethical issues associated with IVF.
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sperm donated may or may not be from legal marriage partner
property of frozen embryos after divorce or death of parents
problems of long-term storage of embryos
post-menopausal pregnancy
ethics of competition for sperm from elite males (eugenics)
Syllabus details—AHL