CHAPTER 18
REVIEW QUESTIONS
18.1
a.
b.
A feedback system is a control mechanism whereby hormones interact with each other in
a coordinated manner to maintain optimum internal conditions, e.g. ACTH secreted by
the anterior pituitary stimulates the adrenal cortex to release cortisone or aldosterone
which regulate aspects of metabolism.
In a positive feedback system, the same response will continue to occur. Thus the
presence of oestrogen maintains the production of FSH and secretion of LH.
In a negative feedback system, the response is reversed or negated, e.g. a rise in the
levels of progesterone inhibits FSH production.
18.2
The hypothalamus is a major sense organ that monitors many body functions. The nerve cells
of the hypothalamus, in addition to producing ADH and oxytocin which are stored in the
neurohypophysis and released under direction from the hypothalamus, produce hormones
which act as release or release-inhibiting chemicals for hormones produced in the anterior
pituitary gland (adenohypophysis). Thus it controls the release of a large number of hormones.
Since five of the seven hormones produced by the adenohypophysis are tropic hormones that
influence other endocrine glands, the pituitary is termed the master gland.
18.3
Thyroxine is a hormone produced by the thyroid gland that increases metabolic rate by
stimulating cell respiration. The production and/or release of thyroxine is under the control of
a hormone, TSH, secreted by the anterior pituitary. When the pituitary is stimulated by the
hypothalamus, it secretes TSH which in turn stimulates the thyroid. Lack of TSH in the blood
inhibits thyroxine secretion.
18.4
The hormones are ‘captured’ by recognition sites on the cell membrane. The interaction
between the recognition site and the hormone bring about changes in specific chemical
reactions by:
 stimulating the activity of specific genes in the nucleus
 influencing the permeability of the cells to particular solutes or
 inducing or repressing cytoplasmic enzymes and thus specific chemical reactions.
18.5
18.6
The membrane of the neurone in the resting state is polarised, i.e. the inside of the membrane
is negative relative to the outside as a result of the active removal of sodium ions. This
removal results in an influx of positively charged potassium ions but large, negatively charged
organic molecules in the cytoplasm maintain the negative internal charge. This results in an
electrical potential difference across the membrane. When an impulse reaches the membrane,
the sodium pump is momentarily broken down and the membrane becomes depolarised.
Sodium ions rush into the neurone at that point along a concentration gradient. When the
membrane potential is reversed (the inside is now positively charged relative to the outside) an
action potential is said to occur. Restoration of the resting potential starts almost immediately
but as this is occurring the action potential stimulates the depolarisation of the adjacent
polarised section of the membrane. Repolarisation begins with an efflux of potassium ions,
followed by the restoration of the sodium pump that results in sodium ions again being
actively removed to the outside of the membrane followed by return of the potassium ions to
the inside. The time during which this occurs is termed the recovery period, during which a
further action potential cannot occur.
18.7
The stimulus for an action potential must be of a minimum strength (the threshold stimulus)
after which an increase in stimulus strength does not alter the magnitude of the action
potential.
18.8
Transmitter substances are only produced at one side (the axonic knob) of the synapse. This
chemical is needed to pass across the synaptic cleft and so stimulate an action potential in the
post-synaptic (dendrite) membrane. Thus the stimulus can only pass in one direction from
neurone to neurone.
18.9
Central Nervous system (brain and spinal cord).
Peripheral Nervous system divided into Somatic (outer body tube) and Visceral (inner body
tube and associated organs) Nervous system, each composed of sensory (input) nerves and
motor (output) nerves. The Visceral motor nerves are further subdivided into Parasympathetic
and Sympathetic systems which have antagonistic effects on the organs they innervate due to
different transmitter chemicals.
18.10
salivary glands – effector
sound – stimulus
message – impulse
brain – central nervous system
18.11
a.
b.
c.
d.
18.12
Sensory neurones take impulses to the central nervous system where they may be relayed to
other parts of the CNS by association neurones for coordination. The response impulse is
transmitted in motor neurones from the CNS to the effector organ.
18.13
A reflex arc is a simple nerve pathway which does not involve coordination, it involves a
sensory neurone which may make direct synaptic contact with the appropriate motor neurone
although an association neurone, taking the impulse to the opposite side of the body or a
different body segment, is usually involved (see Biology: An Australian Perspective Second
Edition textbook, Figure 18.14).
18.14
The energy of the stimulus impinging on the sensory organ (eg. heat, light, pressure,
vibrations, chemicals) is converted into the energy of an action potential by the sense organ.
18.15
The iris, by contraction and expansion, controls the amount of light entering the eye.
18.16
Rods are extremely sensitive to low light intensity. Three different types of cones, each with a
different pigment system, are stimulated by different frequencies of light to effect colour
vision.
cerebrum
spinal cord
cerebellum
medulla oblongata
18.17
The light is reflected from the object and passes through the cornea and into the pupil (the size
of which is determined by the iris) of the eye to the lens. The lens focuses the light rays to
form an image on the retina at the back of the eye. Light sensitive cells in the retina convert
light energy to the energy of an action potential which is transmitted to the optic nerve fibres
and passed to the optic centres of the brain which translate the frequency and number of
messages as a visual image.
18.18
The ear is stimulated by movement of air particles. The vibrations of air are transmitted to
through three bones in the middle ear to the fluid of the inner ear. Within the Organ of Corti in
the inner ear, tufts of hair on sensory cells vibrate in response to different frequencies of
vibration of the fluid. This mechanical energy is then transformed to an action potential which
is sent to the auditory centres of the brain and perceived as sound.
18.19
a.
b.
The alimentary canal has an outer layer of connective tissues continuous with thin
supporting membranes which hold it in position. Inside this layer are two layers of
involuntary muscle, an outer longitudinal and inner circular layer, that are responsible for
peristalsis. The muscle is connected on its inner surface to another connective tissue
layer within which are found the major blood and lymphatic vessels, nerve fibres and
stretch receptors. The inner lining of the alimentary canal consists of smooth muscle
fibres and loose connecting tissue which support the epithelium. Glands are derived from
this epithelium.
The oesophagus is not associated with digestion but merely transfers food through the
thoracic cavity to the stomach. Since the food is in a poorly digested state at this point,
the lining needs to be protected from mechanical damage (rough edges of food, heat,
cold). The epithelium, therefore, is devoid of glands and is thick and stratified, the very
inner layer of cells being dead.
The stomach is a large storage organ in which preliminary digestion of proteins occurs
and which is the major organ of physical digestion. It is therefore an enlarged, sac-like
structure. An additional, oblique, layer of muscles adds to the movement possible by the
stomach, producing the churning of the food to break it into smaller particles for enzyme
action. The lining of the stomach wall is glandular, producing both mucous which
protects the wall from digestive enzymes, and digestive juices (proteolytic enzymes and
acid).
The small intestine is the major site of digestion and absorption of soluble molecules.
The inner epithelium is highly folded, forming finger-like projections called villi and
each of the cells has small projections called microvilli. The villi and microvilli increase
the surface area available for absorption as well as help circulate the food within the
canal. The epithelium is highly glandular, different glands producing enzymes, mucous
and alkaline solutions which aid these digestive enzymes.
The large intestine is involved in the microbial digestion of cellulose, compaction of
undigested food by absorption of water, and egestion. It has an almost smooth epithelial
lining. The muscular sphincter surrounding the anus has an additional layer of striated
muscle so that some voluntary control of egestion can be achieved.
18.20
The walls of the glands and ducts contain protein (e.g. cell membranes, muscles and fibres). If
proteolytic enzymes were produced and secreted in an active form they would start to digest
the glandular cells and their ducts.
18.21
D
18.22
C
18.23
The epithelium is folded (slowing down the movement of chyme) and thrown into finger-like
villi (increase surface area and aid circulation of chyme). Each epithelial cell also has small
projections, the microvilli (further increase surface area for absorption). The villi are highly
vascularised and contain lacteals for the rapid removal of absorbed material.
18.24
Fat digestion begins in the mouth by the physical breakdown by teeth and rolling of the
tongue. Physical digestion continues in the stomach due to the muscular churning created by
the stomach wall. In the duodenum, bile salts from the liver bring about emulsification of the
lipids, breaking them into small droplets with a large surface area : volume ratio. These
droplets are then acted upon by lipases secreted by intestinal glands and the pancreas which
hydrolyse the lipid molecules into fatty acids and glycerol. Very small droplets of lipids and
the fatty acids and glycerol are absorbed into lacteals which join, via larger lymphatic vessels,
with the major vein just prior to its entry into the heart. The molecules are then circulated to
the appropriate cells for assimilation. A small amount of fatty acids and glycerol are also
absorbed directly into the capillaries of the villi.
18.25
a.
b.
c.
d.
e.
18.26
a
b.
c.
Peristaltic contractions are rhythmic movements caused by alternative contraction and
relaxation of the muscles of the alimentary canal wall.
Chyme refers to the state of the food resulting from physical digestion, primarily in the
stomach. The food has been broken down into small particles which has a soupy
consistency. Emulsification is the process whereby fats are dispersed as small droplets in
a water solution. Because of their hydrophobic tails, fat molecules in water tend to clump
together to avoid the repulsive forces between the tails and water. The bile salts are able
to interact with small groups of lipid molecules and reduce the repulsive forces.
Bile salts are involved in physical not chemical digestion – emulsification does not
involve hydrolysis of the lipid molecules, merely separation of large groups of molecules
into smaller groups of molecules.
Pepsin and rennin require a low pH for their optimum operation. The presence of acid
aids in the breaking of binds holding the secondary and tertiary structure of the protein.
It mediates in the conversion of amylose in starch to the disaccharide maltose.
Peristalsis is instigated once food enters the oesophagus. These involuntary contractions
of the muscles move in a wave from the pharynx to the stomach.
Food in the pharynx sparks a reflex action in which causes movement of the epiglottis
across the windpipe and thus entry of food into the oesophagus which starts peristaltic
movement, creating a negative pressure which draws food into it.
Efficient fat digestion requires its emulsification. If the bile duct is blocked this is not
achieved. Thus lipase can only act on the outer edges of large groups of lipid molecules,
having inadequate time in the small intestine to achieve complete digestion.
18.27
The stomach is a storage area, the main function of which is physical digestion and the initial
digestion of proteins. Removal of the stomach does not preclude a fairly normal diet. The
food eaten, however, would need to be of a fine consistency (pre-physically digested) and
taken in small amounts at regular intervals (since storage of large amounts is not possible).
18.28
a.
b.
c.
d.
Rennin.
The rennet causes the milk proteins to come out of solution and clump together.
The stomach.
The clumped proteins are more available for the action of proteolytic enzymes than when
they are in solution.
18.29
a.
b.
The Islets of Langerhans of the pancreas.
They are transported in the blood to the liver which controls blood sugar levels.
18.30
Insulin is secreted directly into the blood system, through which it flows to the liver.
Pancreatic juice is secreted from the Acini cells into the pancreatic duct where it travels
directly to the duodenum.
18.31
To prevent them digesting the glandular tissue and ducts.
1832
The liver is the major site of metabolism of food.
18.33
Each liver lobule is hexagonal in cross-section, composed of cords of cells radiating out from
a central branch of the Hepatic Vein. Between the cords of cells are sinusoids, open spaces
bathed with blood from the capillaries of the Hepatic Portal Artery and Hepatic Artery found
at the corners of each lobule. Bile canaliculi run parallel to the sinusoids, the direction of flow
being opposite to that of the sinusoids. The canaliculi drain into ducts at the edge of the lobule.
18.34
The Hepatic Artery carries oxygen and metabolites whereas the Hepatic Portal Vein is a shortcircuiting vessel, carrying digested food directly from the small intestine.
18.35
The liver is involved in reception and storage of digested food, carbohydrate metabolism,
conversion of excess amino acids, fat metabolism, secretion of bile, storage of iron, vitamins
A, D and B12, manufacture of plasma proteins, production of heat, defence and detoxification.
18.3
18.37
The walls of the trachea (bronchi and major branches) contain incomplete cartilaginous rings
that ensure that the lumen remains open but retains flexibility so that both changes in diameter
and length can occur. The internal surfaces are lined with ciliated epithelium through which
mucous secreting goblet cells are dispersed. The mucous traps small particles of dust, bacteria
and other matter in the air. The beating cilia move the mucous with its trapped particles
towards the pharynx.
18.38
Each alveolus is covered by a capillary network ensuring a large surface area for gas
exchange. The walls of the alveolus and the capillary, both only one cell thick, are in close
contact, being separated by only a thin layer of elastic connective tissue. The diffusion
pathway is therefore very short. The connective tissue allows for expansion and contraction of
the alveolus with ventilation. Some cells in the alveolar wall secrete a lubricating fluid which
decreases the surface tension on the walls and thus helping to keep the alveolar open. Moisture
within the alveolus also allows oxygen to dissolve and so pass readily across the membranes.
18.39
The volume of the thorax is changed via movements of the intercostal muscles and the
diaphragm, creating air pressure differences in the lungs. Air moves into the lungs when the
volume of the thorax is increased (low air pressure relative to the air) and is expired when the
volume of the thorax is decreased (increased air pressure relative to the air).
18.40
Vital capacity is the maximum amount of air that can be ventilated during forced breathing.
Tidal volume is the volume of air moving in and out of the lungs during normal breathing.
18.41
In terrestrial animals the oxygen concentration in the air is relatively high and so levels of
oxygen in the blood can be adequate whilst carbon dioxide can accumulate. The carbon
dioxide reacts with water in tissue fluids and the blood to form carbonic acid which dissociates
into hydrogen and bicarbonate ions. The lowered pH so created can cause enzyme inhibition.
Thus detection and correction of blood pH (which translates into carbon dioxide levels) is
important to terrestrial animals.
18.42
As the level of activity increases, so does aerobic respiration and the production of carbon
dioxide. pH sensors in the major arteries and the tissue fluid surrounding the hind brain
transmit information to the respiratory centres in the hind brain which bring about increases in
the rate and depth of breathing, increasing the rate of gas exchange. These changes are
accompanied by increased heart rate and dilation of the arteries, ensuring a more rapid supply
of blood to the organs undergoing increased activity.
18.43
Lungs are emptied before diving and the dive is rapid. The surrounding water pressure thus
compresses the thorax and lungs, driving alveolar air out of the lungs. The thoracic cavity is
adapted to allow this compression. Nitrogen is thereby prevented from entering the blood. At
pressure nitrogen goes into solution and high concentrations cause narcosis. As pressure
decreases when the animal resurfaces, the nitrogen would come out of solution in the blood,
blocking blood vessels which may result in paralysis (the bends). Other adaptations include:
 Higher blood volume and oxygen-carrying capacity than terrestrial animals – the blood can
be loaded with oxygen by hyperventilation prior to the dive.
 High concentrations of myoglobin in the muscles – myoglobin stores oxygen which can be
used for aerobic respiration when haemoglobin supplies are depleted.
 Blood supply is shunted away from the muscles but maintained to the heart and brain – the
stroke rate of the heart can be decreased, which is less energy demanding whilst
maintaining essential oxygen supply to the brain.
 Vascoconstriction ensures oxygen debt incurred by anaerobic respiration in muscle cells is
restricted to the muscles. The muscle cells can tolerate higher than normal terrestrial lactic
acid accumulation – prevents lactic acid toxicity to other tissues and organs.
18.44
With increased altitude, atmospheric pressure, gas particles, absolute humidity and
temperature decrease. Mammals have a constant body temperature and thus a constant partial
pressure for water vapour and carbon dioxide. At high altitudes with decreased air pressure,
the volume of alveolar space taken up by water vapour and carbon dioxide is high, and the
availability of oxygen decreases more rapidly in the alveoli than in the air.
18.45
Initially there is an increased ventilation rate, which over a period of time is accompanied by:
 correction of blood pH (due to carbon dioxide accumulation) by the kidney
 increased production of red blood cells and haemoglobin
 increase in blood volume and tissue capillaries
 enzyme acquisition which increases the efficiency of oxygen utilisation
 enlargement of the thorax to allow a greater ventilation volume.
18.46
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
n.
o.
p.
q.
r.
s.
t.
u.
v.
w.
x.
y.
artery – thick walled vessel transporting blood away from the heart.
atrium – chamber of heart which receives blood from veins.
atrioventricular valve – tissue found between the atrium and ventricle of the heart to
control the flow of blood.
arterial pressure – blood pressure developed in arteries as it is pumped from the heart by
the contraction of the ventricular wall muscles.
valve – [textbook error: disregard this term]
blood – transporting fluid in animals.
bicuspid valve – atrioventricular valve between the left atrium and ventricle, consisting
of two flaps or cusps.
capillary – small diameter blood vessel whose walls are only one cell thick and through
which exchange of matter with tissue fluid occurs.
coronary vessel – blood vessel servicing the heart muscles.
closed circulation – circulatory system in which the blood is moved throughout the body
in vessels.
diastole – stage in the heart cycle when the muscles are relaxed, allowing the chambers
to fill with blood.
double circulation – circulatory system where the blood passes through the heart twice
each circuit of the body.
lymph – tissue fluid containing a high proportion of white blood cells which has been
taken up by the lymphatic vessels to be returned to the blood vascular system.
plasma – fluid part of the blood composed of serum (water in which proteins and
dissolved substances are suspended) and fibrinogen.
platelet – cell fragments found in the blood, which are involved in the clotting process.
portal vein – a vessel which starts and ends in a capillary bed.
red blood cell – blood cell specialised for the transport of respiratory gases by the
inclusion of the pigment haemoglobin; enucleate in mammals.
serum – plasma minus fibrinogen.
semilunar valve – flaps of tissue found at the origin of the arteries leaving the heart, that
prevents backflow of blood during diastole.
systole – stage in the heart cycle when the muscles are contracted and blood is forcible
ejected into the arteries.
tissue fluid – fluid formed from plasma pushed out through the walls of the capillaries
under arterial pressure; surrounds cells, providing a medium for exchange between the
cells and blood.
tricuspid valve – right atrioventricular valve consisting of three cusps.
vein - thin walled blood vessel which returns blood to the heart.
ventricle – highly muscular chamber of the heart provides pressure for blood to circulate
in arteries.
venule – small branch of a vein formed by joining of capillaries.
18.47
Plasma – transport of nutrients, waste products, hormones and heat.
Red blood cells – transport of respiratory gases.
White blood cells
Neutrophils – phagocytes
Eosinophils – allergic reaction
Basophils – inflammation reactions; produce heparin - prevent to
clotting
Lymphocytes – antibody formation
Monocytes – phagocytic
Platelets – release fibrin from fibrinogen in clotting of blood.
18.48
Fibrinogen is the soluble, inactive pre-cursor substance which forms insoluble fibrin when
activated. Fibrin brings about clotting of the blood.
18.49
a.
b.
Oxygen combines with haemoglobin to form oxyhaemoglobin. This is a loose union
that allows rapid detatchment of the oxygen when the concentration of oxygen (as in
capillaries in tissues) is low and attachment when the concentration (as in the
capillaries of the lung) is high.
Carbon dioxide is mostly transported as bicarbonate ions in the red blood cells
although some is combined with haemoglobin.
18.50
a.
b.
The uptake and release of oxygen by haemoglobin is determined by the pH of the blood
and the amount of oxygen present in the plasma. Changes in pH result from the presence
or absence of carbon dioxide. When carbon dioxide is present it combines with water to
form carbonic acid. This dissociates into hydrogen and bicarbonate ions. A low pH
favours unloading of oxygen from haemoglobin. Thus in the alveoli of the lungs, the
carbon dioxide tension is low and oxygen tension is high. Carbon dioxide is reformed
from bicarbonate and hydrogen ions and diffuses out of the blood. Oxygen passes into the
blood along the diffusion gradient where it combines with haemoglobin.
In actively respiring tissues, and thus the surrounding tissue fluid, carbon dioxide tensions
are high and oxygen tensions are low relative to the plasma in the capillaries. Carbon
dioxide diffuses into the red blood cells where it forms carbonic acid. The lowered pH
causes the haemoglobin to release oxygen molecules which then pass into the tissue fluid
along the diffusion gradient.
18.51
In the alveoli of the lungs the oxygen tension is high and carbon dioxide tension low relative
to the blood. Carbon dioxide passes out of the blood into the alveoli and oxygen enters the
blood and red blood cells. With low carbon dioxide and high oxygen in the red blood cells,
haemoglobin uptake of oxygen is very rapid. In the tissue fluid of respiring cells surrounding
capillaries, carbon dioxide tension is high and oxygen low. Carbon dioxide diffuses into the
blood and red blood cells where it forms carbonic acid. The lowered pH results in very rapid
unloading of oxygen which then diffuses into the tissue fluids.
18.52
The Bohr shift is a shift to the right of the oxygen dissociation curve when carbon dioxide
levels are increased – oxygen is only loaded when its tensions are higher than normal in the
red blood cells and conversely it is unloaded at higher than normal oxygen levels.
18.53
Excess bicarbonate ions formed by the dissociation of carbonic acid in the red blood cell pass
into the plasma. The membrane is relatively impermeable to positive ions so that unless
another negative ion (chloride) enters the red blood cell, there would be an ionic imbalance in
the red blood cell.
18.54
a.
b.
1
2
3
4
5
6
7
8
9
i.
right ventricle
tricuspid valve
right atrium
semilunar valve
dorsal aorta
left atrium
bicuspid valve
left ventricle
muscular wall of left ventricle
9 is thicker than 1 – it needs to exert a greater pressure to force the blood right around
the body rather than just to the lungs (1).
ii. 9 is much thicker than 6 since the atrium is merely a receiving chamber that
transfers blood to 9.
c.
Structure
1
3
8
9
2
18.55
a.
b.
c.
18.56
Condition
Relaxing

Contracting




Changes in the internal environment are monitored by the brain and appropriate changes
to the rate of contraction of cardiac muscle can be achieved.
Sympathetic nerve activation increases heart beat and Parasympathetic nerve activation
decreases it.
The nerves stimulate a specific part of the muscle of the right atrium – the sino-atrial
node (pacemaker), causing a series of chemical changes in the muscle cells which result
in contraction. The chemical changes pass from muscle cell to cell bringing about a wave
of muscular contraction across the atrium walls. At the atrioventricular node (the only
part of the atrium not separated from the ventricle by connective tissue) the wave of
contraction is passed on to the ventricles via the Purkinji fibres. Thus systole starts with
contraction of the atria (blood flows into the ventricles), followed by ventricular
contraction (the atria relax and atrioventricular valves close to prevent backflow of blood
so that blood is forced into the arteries) and ventricular relaxation (diastole which is
associated with closing of the semilunar valves and opening of the atrioventricular
valves).
Blood pressure is a measure of the pressure exerted on the blood in the arteries by the action
of cardiac muscle. When the muscle contracts, it decreases the volume of the ventricle, and
thus increases pressure, forcing blood into the arteries. During diastole, there is not further
pressure exerted on the blood in the arteries by the heart, thus it decreases. The high number in
the reading (140) indicates systolic pressure whilst the low number (85) indicates diastolic
pressure.
18.57
Fluid
Plasma
Tissue fluid
Lymph
Structure
Serum (water plus globular proteins
and dissolved substances) plus
fibrinogen.
Water and dissolved substances.
Tissue fluid with a large number of
white blood cells and lipid
molecules.
Function
Transport of nutrients,
products, hormones and heat.
waste
Exchange of materials between the
blood and the cells.
Absorption of fatty acids and
glycerol from small intestine; return
of tissue fluid to the heart;
phagocytosis of foreign matter.
18.58
a.
b.
18.59
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
n.
A system where two vessels (or a vessel and movement of the external environment), in
close parallel proximity, transport material in opposite directions.
Blood flowing in an artery from the warm, central body core to the cold extremities will
lose heat to the environment. If the vein returning cold blood from the extremities runs in
a counter-current to the artery, heat will be transferred from the artery all along the
length of the vein which will be at a lower temperature and thus heat loss to the
environment is minimised.
Bowman’s capsule – the cup-shaped beginning of the nephron, through which blood is
filtered under pressure.
pyramid – conical shaped lobe of the kidney medulla.
isotonic – having the same concentration as that of the surroundings.
ureter – duct formed by the collecting ducts draining the nephrons which transports urine
to the bladder.
cortex – outer, dark-coloured layer of the kidney.
ultrafiltration – filtration of blood out of a capillary under higher than normal blood
pressure.
medulla – the inner, lighter-coloured layer of the kidney which surrounds the central
cavity.
hypertonic – at a higher concentration than the surroundings.
hypotonic – at a lower concentration than the surroundings.
convoluted tubule – highly coiled tubules of the nephron on either side of the loop of
Henle.
loop of Henle – a U-shaped portion of the nephron in which water is reabsorbed.
glomerulus – group of blood capillaries through which ultrafiltration into Bowman’s
capsule occurs.
urethra – the tube through which urine passes from the bladder to the external
environment.
pelvis – the expanded proximal portion of the ureter within the central cavity of the
kidney.
18.60
As evaporation from the skin, on expiration and in urine.
18.61
A: urethra.
18.62
C: cortex.
18.63
a.
b.
c.
d.
e.
f.
g.
h.
renal artery
glomerulus
nephron (Bowman’s capsule)
plasma proteins
mineral salts
sodium chloride molecules
osmosis
sodium chloride
18.64
a.
b.
c.
d.
Large amount of dilute urine.
Scant, concentrated urine.
Scant, concentrated urine.
Scant urine of ‘normal’ concentration.
18.65
a.
b.
Removal of metabolic wastes.
Maintenance of the correct water balance.
i.
j.
k.
l.
m.
n.
o.
p.
ascending
tissue fluids
hypertonic
hypothalamus
brain
ADH
decreases
less