The Circulatory System
NEED FOR TRANSPORT INSIDE THE BODY
Every organ in our body requires the involvement of the
circulating body fluids.
For example :
• The digestive system digests and absorbs nutrients
which are needed to be transported to every cell of the
body.
• The respiratory system draws in air, and the oxygen
picked up from it in the lungs has to be transported to all
parts of the body. Similarly, the CO₂ collected from the
entire body has to be carried to the lungs to be exhaled
out of the body.
• All the extra water, excess salts, and the nitrogenous
wastes such as urea have to be removed from different
parts and have to be sent to the excretory system to be
thrown out of the body.
• Hormones secreted by the endocrine system have to be
carried throughout the body by the circulating blood to
act wherever required, and so on.
FLUIDS IN OUR BODY
There are three principal fluids in
our body :
(i) Blood, contained in the heart
and in the blood vessels (arteries,
veins and capillaries) of the
circulatory system.
(ii) Tissue fluid, occupying spaces
between cells in the organs.
(iii) Lymph, which is contained
within lymph vessels and
lymphatic organs such as the
spleen and the tonsils.
PROPERTIES OF BLOOD: THE BLOOD
i) Never Stationary - Blood is always in
motion from the heart to the arteries and
back through the veins.
ii) Color - The blood is a somewhat thick fluid,
bright red when taken from an artery or dark
red when taken from a vein.
iii) Volume -An average adult human has 5 to
6 litres of blood by volume in his body.
iv) Taste - saltish Perhaps we have all
"tasted" our blood as in the case when there
is a cut in the tongue or bleeding from the
gums.
FUNCTIONS OF BLOOD
The main functions of the blood in our body
can be treated under two broad headings:
(A) Transport By Blood:
(Transport of digested
food, oxygen, carbon dioxide, excretory
substances, hormones, body heat).
1. Transport of digested food
2. Transport of oxygen
3. Transport of carbon dioxide
4. Transport of excretory material
5. Distribution of hormones
6. Distribution of heat
B. PROTECTION BY BLOOD:
1. Blood forms a clot wherever
there is a cut in a blood vessel.
The clot serves to prevent
(i) further loss of blood
(ii) the entry of disease-causing
germs.
COMPOSITION OF BLOOD
The blood consists of:
i) Plasma - fluid part, constitutes 55-60 per
cent of blood.
ii) Cellular elements - red and white cells, and
platelets, 40-45 per cent of blood.
PLASMA -
The plasma is a light-yellow
coloured, alkaline liquid. It mainly consists of
water, proteins, inorganic salts and other
substances. The plasma from which the
protein fibrinogen has been removed is called
serum.
Cellular Elements:
The formed or cellular elements of
the blood (i.e. shaped structures
visible under magnification) are of
three categories:
(1) Red blood cells (erythrocytes)
(2) White blood cells (leukocytes)
(3) Blood platelets (thrombocytes)
(1) Red Blood Cells (RBCs):
i) These are minute biconcave disclike structures flat in the centre
and thick and rounded at the
periphery.
ii) These are very small about 7
micron in diameter (1 micron = onethousandth of a millimetre and is
represented by the symbol “µ”)
iii) The small size plus the
concavities on either side provide a
large surface area which makes
them very efficient in absorbing
oxygen.
HAEMOGLOBIN is the effective
chemical constituent of RBCs. The red
blood cells have a colorless spongy
body or stroma which contains a
respiratory pigment hemoglobin (Hb).
Haemoglobin has very strong affinity
for carbon monoxide forming a stable
compound carboxyhemoglobin (HbCO).
Life and death of RBCs:
i) In adults, the RBCs are produced in the
marrow of long bones, especially in the ribs,
breast bone and ilium of hip girdle.
ii) In an embryo they are produced in the
liver and spleen.
iii) The mature red blood cells have no
nuclei.
iv) The average life of an RBC is about 120
days.
v) The old and weak red blood cells are
destroyed in the spleen, liver and bone
marrow.
Mammalian Red Blood Cells:
Mammalian red blood cells when mature
circulate in the blood system and are
devoid of certain organelles. They
i) have no nucleus
ii) no mitochondria
iii) no endoplasmic reticulum
*Abnormally increased number of RBCs
is called Polycythaemia, and their
abnormally decreased number is known
as Erythropenia.
(2) WHITE BLOOD CELLS (WBCs) –
White blood cells, or leukocytes (leuko:
white), differ from red blood cells in having a
nucleus and not containing haemoglobin.
Their number is much less, usually about
4000-8000 per mm³ of blood.
Origin and life of WBCs:
The WBCs are produced in red bone marrow,
lymph nodes and sometimes even in liver and
the spleen Their average life is about two
weeks.
Functions Of Leukocytes (WBCs) Body defence:
1. Phagocytosis: This is a process in
which most WBCs and particularly the
neutrophils engulf particle-like solid
substances, especially bacteria.
2. Inflammation: Inflammation occurs
due to the reaction of tissues to injury
and to localized invasion of germs.
3. Formation of antibodies
(3) BLOOD PLATELETS (Thrombocytes) (Initiators of clotting of blood)
Blood platelets are minute oval or round
structures, non-nucleated, floating in the
blood. These are about 200,000 to
400,000 per cu. mm. of blood in an adult.
The platelets are derived from some
giant cells called megakaryocytes in the
red bone marrow. Their life span is 3 to 5
days and are destroyed mainly in the
spleen.
BLOOD TRANSFUSION AND BLOOD GROUPS (ABO and Rh systems)
ABO System:
According to
the ABO system, the human
blood is classified into four
types - A, B, AB and O.
Rh system: (Rh stands for
Rhesus, our common
monkey, in which the factor
was first discovered).
The Excretory System
Excretion:
The process of removal of chemical
wastes (mainly nitrogenous wastes) from
the body is known as 'excretion'. Excretion
plays an important role in maintaining the
homeostatic (steady state) condition of the
body.
Excretory System:
Organs which are concerned with the
formation, storage and elimination of urine
constitute the 'excretory system'.
Substances to be eliminated:
1. Carbon dioxide and water
- Carbon dioxide is eliminated through the lungs.
- The extra water is released out of the body. in the
form of sweat.
2. Nitrogenous Wastes
- These include urea, uric acid and ammonia.
- Urea is excreted out through the kidneys.
3. Excess salts such common salt (NaCl) and even
some excess water-soluble vitamins (B and C) need to
be eliminated.
- Salts are mainly given out through the kidneys.
4. Water is taken in with food and beverages,
in large quantities.
5. Bile pigments (chiefly yellow bilirubin) are
the breakdown products of the hemoglobin of
the dead RBCs.
- Excreted in urine.
The Excretory Organs:
1. Kidneys: These are the primary excretory
organs eliminating nitrogenous wastes in the form
of urine.
2. Skin: Sweat excreted by the sweat glands of the
skin primarily excrete water and sodium chloride.
3. Lungs: They excrete carbon dioxide.
4. Liver: Liver detoxifies ammonia by converting it
to urea.
Kidneys
The kidneys are two bean-shaped organs
located on either side of the backbone and
protected by the last two ribs.
A tube, the
ureter, arises from the notch (hilum) connects
behind with the urinary bladder.
The front end
of the ureter is somewhat expanded into the
kidney and is called the pelvis.
The urine
produced in the kidneys collects in the
urinary bladder to the outside of the body
through the urethra.
A sphincter (circular
muscle) guards the opening of the bladder
into the urethra and relaxes only at the time
of urination (micturition) under an impulse
from the brain.
Internal Structure of the Kidneys
A longitudinal section of the kidney
shows two main regions-an outer dark
cortex and an inner lighter medulla.
The
medulla is composed of a finely striped
substance arranged in several conical
pyramids. The apex of each pyramid is
called papilla.
The kidney is composed
of an enormous number of minute
tubules called uriniferous tubules or
nephrons.
These are the structural as
well as functional units of the kidney.
Structure of a Kidney Tubule
Bowman's capsule is a thin-walled cup.
The
outer concavity of the cup lodges a knot-like
mass of blood capillaries, called glomerulus.
Proximal or first convoluted tubule (PCT)
It is
the starting convoluted region of the tubule.
Middle U-shaped part (Loop of Henle) is
shaped like a hair-pin.
Distal convoluted tubule (DCT)
It is the end part
of the kidney tubule. It opens into a collecting
duct.
Blood supply to the Kidney Tubules:
Each such arteriole enters a
Bowman's capsule under the
name of afferent arteriole. This
afferent arteriole breaks into a
number of capillaries. The
reuniting capillaries of the
glomerulus form the efferent
arteriole.
Functions of the Kidney - Production of
Urine:
The production of urine occurs in three
major steps:
(I) ultrafiltration
(II) reabsorption
(III) tubular secretion
(I) Ultrafiltration
The blood flows through the
glomerulus under great
pressure which is much greater
than in the capillaries
elsewhere.
This filtration under
extraordinary force is called
ultrafiltration.
The fluid
entering the renal tubule is
called the glomerular filtrate.
The glomerular filtrate consists
of water, urea, salts, glucose
and other plasma solutes.
(II) Reabsorption:
The glomerular filtrate
entering the renal tubule is
not urine.
It is an
extremely dilute solution
containing a lot of useful
materials including
glucose and some salts
such as those of sodium.
The normal concentration
of the blood is not
disturbed.
This is called
selective absorption.
(III) Tubular Secretion:
Certain substances
like potassium (K+)
and a large number of
foreign chemicals are
passed into the
forming urine.
This
passage involves the
activity of the cells of
the tubular wall, and
hence it is called
tubular secretion.
Physical properties of urine- -
Colour: Clear yellow (due to pigment urochrome).
Volume: 1 to 1.5 litres per day but varies.
pH: 5 to 8
- Odour: ammonia-like
Specific gravity: 1.003 to 1.035
CONSTITUENTS OF URINE
The normal human urine consists of about 95% of water
and 5% of solid wastes dissolved in it.
Abnormal constituents in urine
(i) Blood cells: Known as haematuria
(ii) Glucose In a condition called glycosuria.
(iii) Albumin: This condition is termed as albuminuria.
(iv) Bile pigments: Due to anaemia, hepatitis (jaundice) or
liver cirrhosis, urine may contain bile pigments.
REGULATION OF URINE OUTPUT
The pituitary gland and Diuresis (increased
production of urine) - Concentration of the
urine by water reabsorption is controlled by
antidiuretic hormone (ADH) secreted by the
posterior lobe of the pituitary gland.
OSMOREGULATION
The kidney while removing wastes like urea
from the blood also regulates its composition,
i.e., the percentage of water and salts. This
function is called osmoregulation it implies
the regulation of osmotic pressure of the
blood.
ARTIFICIAL KIDNEY:
If one kidney is
damaged or
removed for some
reason, the other
kidney alone is
sufficient for
excretory needs and
the person can lead
a normal life.
Artificial kidney is a
dialysis machine.
THE NERVOUS SYSTEM
Neuron:
Our nervous system consists of brain, spinal cord, sense receptors
and a whole lot of nerves. The brain and spinal cord are made up of
neurons or nerve cells.
Structure of the neuron:
The three main parts of a neuron are the
cell body, dendrites and axon.
(i) The cell body (Perikaryon or Cyton) (peri : surrounding, karyon :
nucleus)
• It contains a well-defined nucleus, surrounded by granular
cytoplasm.
• It has all the cell organelles like other cells, only centrosome is
absent because nerve cells have lost the ability to divide.
(ii) Dendrites (dendron tree/branch):
These are branched cytoplasmic projections of the cell body. They
conduct nerve impulses to the cyton.
(iii) Axon:
• It is a long process from the cell body.
• It varies in size from a few millimeters to even more than one
metre in length.
Two major divisions of the Nervous System:
1. Central Nervous System (CNS) includes the brain
and the spinal cord contained within the vertebral
column.
2. Peripheral nervous system (PNS) includes the
nerves that emerge from and enter into the brain and
spinal cord.
The PNS consists of two subdivisions :
A. Somatic nervous system (SNS) conveys
information to skeletal (voluntary) muscles.
B. Autonomic nervous system (ANS) includes a pair
of chains of ganglia and nerves which control the
involuntary actions of many internal organs (smooth
muscles, heart muscles and glands).
The Brain:
The brain is a very delicate
organ well protected inside the brain
box or cranium of the skull.
Coverings:
The brain is protected by 3
membranous coverings called meninges
(meninx: membrane) which continue
backwards on the spinal cord.
(i) Dura mater - the outermost tough
fibrous membrane (dura : tough, mater:
mother).
(ii) Arachnoid the thin delicate middle
layer giving a web-like cushion (arachne
: spider).
(iii) Pia mater the innermost highly
vascular membrane, richly supplied
with blood (pia: tender).
1) CEREBRUM (cerebrum: brain)
The cerebrum is the largest portion of the
brain. It is divided into two (right and left)
halves called cerebral hemispheres. Their
outer surface is highly convoluted with ridges
and grooves. Each cerebral hemisphere is
hollow internally and the walls have two
regions - an outer(cortex) and an inner portion
(medulla). The outer portion (cortex) of the
cerebrum contains cell bodies of the neurons
and, being grayish in colour, is called the gray
matter. . It is the layer of gray matter which is
folded to form the convolutions. The folds are
called gyri and the grooves are called sulci
(creases). Such a system increases surface
area to accommodate more nerve cells.
2) CEREBELLUM ("little brain")
The cerebellum is a much smaller area of the
brain located just at the base and under the
large cerebrum. It has no convolutions, but has
numerous furrows. This also has an outer
cortex made of gray matter. Centrally, it has
white matter which, in a median section,
appears like a branching tree. The main
function of the cerebellum is to maintain
'balance' of the body and coordinate muscular
activity. The impulse for performing a muscular
act, originates in the cerebrum and not in the
cerebellum. For example, if you stand up and
walk, the impulse for this activity arises in the
cerebrum (conscious part). The act of walking
involves coordinated working of many muscles.
Proper coordination and timing of their
contraction and relaxation is the responsibility
of the cerebellum.
3) MEDULLA OBLONGATA
The medulla oblongata is the
lowest portion of the brain located
at the base of the skull. It is
roughly triangular and is continued
behind as the spinal cord. Its
function is to control the activities
of the internal organs, for example,
peristaltic movement of the
alimentary canal, movement of
breathing, beating of the heart and
many other involuntary actions.
Injury to the medulla generally
results in death.
Three Primary Regions of the Brain:
All parts taken together, the brain may be said to consist of three
primary regions forebrain, midbrain and hindbrain. The various parts
under each region and their principal functions are as follows:
1. Forebrain:
a) Cerebrum (cerebral hemispheres) (seat of intelligence, memory,
consciousness, will power, voluntary actions).
b) Diencephalon
(i) Thalamus (relays pain and pressure impulses to cerebrum).
(ii) Hypothalamus (controls the body temperature and pituitary).
2. Midbrain: A small tubular part (reflexes involving eyes and ears).
3. Hindbrain:
a) Cerebellum (coordinates muscular act balance of the body).
b) Pons located in the centre of the - below the cerebellum (carries
impulses one hemisphere of the cerebellum to the hemisphere and
coordinates muscular movements on both the sides of the body).
c) Medulla oblongata (controls activities of internal organs, heart beat,
breathing, etc.)
The spinal cord
The spinal cord extends from the medulla of the brain down almost the whole
length of the backbone to end at the second lumbar vertebra and lies within the
neural canal of the vertebrae.
The internal structure of the spinal cord in a cross
section.
Here the arrangement of white and the matter is reversed from that in
the brain.
The matter containing the cell bodies of motor (efferent) and
association neurons lies on the inner side and the white matter on the outer
side.
The white matter contains axons running longitudinally to and from the
brain and even crossing from one side to the other.
There is a small central
canal in the centre which runs the entire length and is continuous with the
cavities of the brain.
It is also filled with cerebrospinal fluid which acts as a
shock proof cushion and forms a medium for the exchange of food materials,
waste products, and respiratory gases with neurons.
Externally, the
spinal cord is covered by the same three membranes dura mater, arachnoid and
pia mater in continuation with those of the brain.
Functions of the Spinal Cord
The spinal cord is concerned with the following three
functions:
(i) Reflexes below the neck.
(ii) Conducts sensory impulses from the skin and muscles
to the brain.
(iii) Conducts motor responses from the brain to muscles
of the trunk and limbs.
Reflexes (Involuntary Actions)
The term “reflex” comes from the Latin word
“reflexus” meaning reflected or directed
back.
Two types of actions which occur in our body
are:
1. Voluntary Actions
2. Involuntary Actions
Sense Organs
The sense organs enable us to
be aware of the conditions of
our external as well as internal
environment.
RECEPTORS
Receptor is any specialized tissue or cell
sensitive to a specific stimulus.
(i) Mechanoreceptors - are receptors for touch,
pressure of skin due to mechanical change.
(ii) Chemoreceptors - receptors of taste of the
and smell of the nose due to chemical influences
(iii) Photoreceptors - are rods and cones of the
retina of eye due to light.
(iv) Thermoreceptors are heat and cold
receptors in the skin, due to change in
temperature.
(v) Phonoreceptors - receptors for sound/hearing.
THE EYES
Orbits: The two eyes are located in
deep sockets or orbits on the front
side of the head.
Eyelids: protect the outer (front)
surface of the eyes and can shut out
light.
Eyebrows: prevent the rain drops or
the trickling perspiration from getting
into the eyes.
Tear glands: pour the secretion over
the front surface.
Tear ducts:
A nasolacrimal duct conducts the
secretion into the nasal cavity.
Functions of Tears:
1. Lubricate the surface of the eye.
2. Wash away dust particles.
3. Help in killing germs.
4. Communicate emotions
Conjunctiva:
It is a thin membrane covering the
entire front part of the eye.
Structure of the
Eyeball:
(1) outer sclerotic
(2) middle choroid
(3) inner retina
YELLOW SPOT -
The area of best
vision
The region of brightest vision and
also of the color vision. Yellow spot is the place of best vision of the
normal eye. This is the reason why
you move your eyes from word to
word as you read a line through a
printed page.
BLIND SPOT -
The area of no vision
There are no sensory cells here
and, therefore, this is the point of
no vision.
Lens:
The lens is a transparent,
flexible, biconvex crystalline
body located just behind the
pupil. The lens is collectively
held in position by fibres called
the suspensory ligament, which
attaches it to the ciliary body.
TWO CHAMBERS OF THE EYE
1. AQUEOUS CHAMBERS
2. VITREOUS CHAMBERS
Common Defects of the Eye:
1. Near or short-sightedness (Myopia): This defect
can be corrected by suitable concave (diverging) lens which causes the light rays to diverge before they
strike the lens of the eye.
2. Far or long-sightedness (Hyperopia, old term
Hypermetropia): A convex (converging) lens is
required to correct it.
3. Astigmatism: This is corrected by cylindrical
lenses.
4. Presbyopia: This again is corrected by a convex
lens.
5. Cataract: It can be corrected by surgically
removing the lens, and by using spectacles
with highly convex lenses.
6. Night-blindness: This is usually due to the
deficiency of Vitamin A.
7. Color blindness: This is due to a genetic
defect.
8. Corneal opacities: defects can cause
anything from minor irritation to vision
problems and even blindness.
9. Squint: Surgery and suitable exercise can
correct these defects.
THE EAR -
ORGAN FOR HEARING AND BALANCE
The human ear is concerned with two
functions, hearing and body balance.
It has three main divisions:
(i) outer ear
(ii) middle ear
(iii) inner ear.
Functions of the Ear:
The internal ear is involved in two
sensory functions:
A. HEARING
Organ of Corti
B. BALANCING
Static: utriculus and sacculus
Dynamic: ampulla
The Endocrine System
Endocrine glands secrete certain chemicals
known as hormones. Hormones are
extremely important secretions for the
regulation of body activities.
Hormones
are secretions from specific
cells or glands in the body, and are carried
to all parts through blood, but their effect is
produced in one or more specific parts
(target organ or cells) only. Most hormones
are secreted by special glands, the
endocrine glands (endo: inside, crine:
separate) meaning "secrete internally",
also called ductless glands because their
secretions are poured directly into the
blood and not through any special duct.
Endocrine System
Endocrine system consists of
several glands/glandular cells
which bring about the overall
common function of chemical
coordination in the body. They
activate each other and work as a
system of organs called
endocrine system. A system is
defined as a group of organs
performing an overall common
function. Endocrine glands
secrete certain chemicals called
hormones.
General Properties of Hormones:
1. Hormones are secreted from their source
(an endocrine gland) directly into the blood.
2. They act on target organs or cells usually
away from their source.
3. Hormones are not stored in the body and
are excreted from the system.
4. Hormones produced in one species usually
show similar influence in other species.
Endocrine Glands:
The principle endocrine
glands in the human
body are:
1. Adrenal
2. Pancreas
3. Thyroid
4. Pituitary
1. Adrenal Glands
The adrenal glands are like caps on the
top of each kidney (ad: near, renal: kidney).
Each adrenal gland consists of two parts –
(i) a central medulla
(ii) a peripheral cortex
i) Adrenal Medulla secretes adrenaline. Adrenaline is a hormone,
which prepares the body to meet any emergency situation, for
"fight" i.e. to face danger or for "flight", to run away from it.
ii) Adrenal Cortex secretes many hormones but the best known
hormone is cortisone.
The cortical hormones are categorised as:
a) Mineralocorticoids: regulates mineral metabolism, specially Na+
and K+ ions.
b) Glucocorticoids: regulates carbohydrate, protein and fat
metabolism.
2. Pancreas
Pancreas is both
a duct gland as
well as a ductless
gland. As a ductless gland, it has
special groups of hormone-secreting
cells called/ Islets of Langerhans. The
islet cells produce three hormones
insulin, glucagon and somatostatin.
(1) Insulin secreted by beta cells checks rise
of sugar level in blood.
Under Section of Insulin
Insufficient secretion of insulin causes
diabetes (more correctly diabetes mellitus or
hyperglycemia). The word "mellitus" means
honey, referring to the passage of sugar
(glucose) in urine.
Over Section of Insulin
Over-secretion of insulin causes hypoglycemia
and coma.
3. Thyroid
The two lobes
are joined by a
narrow isthmus
(interconnection). It
secretes two hormones thyroxine and
calcitonin. Thyroxine regulates the
basal metabolism, i.e., the rate of
cellular oxidation resulting in heat
production at rest.
4. Pituitary
The pituitary gland is a
small projection (about
the size of a pea) which
hangs from the base of
the mid-brain below
hypothalamus. It is
popularly called the
master gland because it
seems to control
practically all other
endocrine glands.
A. HORMONES FROM ANTERIOR PITUITARY
1. Growth hormone (GH) is essential for
normal growth. It is also called
somatotropin (somatic: body, tropic:
stimulating).
2. Thyroid stimulating hormone (TSH)
activates thyroid to secrete thyroxin.
3. Gonad stimulating (Gonadotropic)
hormones regulate the activities of the
testes and ovaries.
4. Adrenocorticotropic hormone (ACTH)
regulates the activity of adrenal cortex.
B. HORMONES FROM POSTERIOR PITUITARY
The posterior lobe produces two
hormones named vasopressin and
oxytocin.
1. Antidiuretic hormone (ADH), also
called vasopressin.
2. Oxytocin (Gk. oxys: sharp/quick, tokos
: childbirth) stimulates vigorous
contractions of the uterus in a pregnant
mother
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