Sunday, 20 April 2014
Wednesday, 16 April 2014
TRANSPORT
Functions Of Blood
Circulatory System
Blood circulates in two
linked circuits: the pulmonary, which carries blood to the lungs to be
oxygenated, and the systemic, which supplies oxygenated blood to the body.
Arteries carrying blood from the heart divide into smaller vessels called
arterioles and then into capillaries, where nutrient and waste exchange occurs.
Capillaries join up to form venules,
which in turn join to form veins that carry blood back to the heart. The portal
vein does not return blood to the heart but carries it to the liver.
In
both the pulmonary and systemic circulations, the exchange of oxygen,
nutrients, and waste products occurs in the capillaries that join arterioles to
venules.
The heart powers the
pulmonary and the systemic circulations. In the pulmonary circulation, deoxygenated
blood (blue) travels to the lungs, where it absorbs oxygen before returning to
the heart. This oxygenated blood (red) is pumped around the body in the
systemic circulation. Body tissues absorb oxygen, and deoxygenated blood
returns to the heart to be pumped to the lungs again.
The blood pressure in the
veins is about a tenth of that in the arteries. Various physical mechanisms
ensure that there is adequate venous return (blood flow back to the heart).
Many deep veins lie within muscles. When the muscles contract, they squeeze the
veins and force blood back to the heart. The action of inhalation during
breathing also draws blood to the heart. In addition, venous return from the
upper body is assisted by gravity.
Human Skeletal System
Human Skeletal System
Human skeleton is the internal framework of the body.
It is composed of 270 bones at birth [1][2][3] – this total decreases to 206 bones by
adulthood after some bones have fused together. The bone mass in the skeleton reaches maximum
density around age 30. The human skeleton can be divided into the axial
skeleton and the append circular skeleton. The axial skeleton is formed by the vertebral column, the rib
cage and
the skull. The append circular skeleton, which is attached to the axial skeleton,
is formed by the pectoral
girdles, the pelvic
girdle and
the bones of the upper and lower limbs.
The human
skeleton serves six major functions; support, movement, protection, production
of blood cells, storage of ions and endocrine regulation.
The human
skeleton is not as sexually
dimorphic as that of many other primate species, but subtle differences between
sexes in the morphology of the skull, dentition, long
bones, and pelvis
exist. In general, female skeletal elements tend to be smaller and less robust
than corresponding male elements within a given population. The pelvis in
female skeletons is also different from that of males in order to facilitate
child birth.
The skeleton serves six major
functions; support, movement, protection, production of blood cells, storage of
minerals and endocrine regulation.
The joints between bones
allow movement, some allowing a wider range of movement than others, e.g. the
ball and socket joint allows a greater range of movement than the pivot joint
at the neck. Movement is powered by skeletal muscles, which are attached to the skeleton at various sites on
bones. Muscles, bones, and joints provide the principal mechanics for
movement, all coordinated by the nervous system.
Down Syndrome
Down Syndrome
Down syndrome is a chromosomal condition that is associated
with intellectual disability, a characteristic facial appearance, and weak
muscle tone (hypotonia) in infancy. All affected individuals experience
cognitive delays, but the intellectual disability is usually mild to moder
ate.
People with Down syndrome may have a variety of birth
defects. About half of all affected children are born with a heart defect.
Digestive abnormalities, such as a blockage of the intestine, are less common.
Individuals with Down syndrome have an increased risk of
developing several medical conditions. These include gastroesophageal reflux,
which is a backflow of acidic stomach contents into the esophagus, and celiac
disease, which is an intolerance of a wheat protein called gluten. About 15
percent of people with Down syndrome have an underactive thyroid gland
(hypothyroidism). The thyroid gland is a butterfly-shaped organ in the lower
neck that produces hormones. Individuals with Down syndrome also have an
increased risk of hearing and vision problems. Additionally, a small percentage
of children with Down syndrome develop cancer of blood-forming cells
(leukemia).
Delayed development and behavioral problems are often
reported in children with Down syndrome. Affected individuals' speech and
language develop later and more slowly than in children without Down syndrome,
and affected individuals' speech may be more difficult to understand.
Behavioral issues can include attention problems, obsessive/compulsive
behavior, and stubbornness or tantrums. A small percentage of people with Down
syndrome are also diagnosed with developmental conditions called autism
spectrum disorders, which affect communication and social interaction.
People with Down syndrome often experience a gradual decline
in thinking ability (cognition) as they age, usually starting around age 50.
Down syndrome is also associated with an increased risk of developing Alzheimer
disease, a brain disorder that results in a gradual loss of memory, judgment,
and ability to function. Approximately half of adults with Down syndrome
develop Alzheimer disease. Although Alzheimer disease is usually a disorder
that occurs in older adults, people with Down syndrome usually develop this
condition in their fifties or sixties.
Type of Blood Groups
Type of Blood Groups
A blood type (also called a blood group) is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of red blood
cells (RBCs). These
antigens may be proteins, carbohydrates, glycoproteins,
orglycolipids,
depending on the blood group system. Some of these antigens are also present on
the surface of other types of cells of
various tissues.
Several of these red blood cell surface antigens can stem from one allele (or very closely linked genes) and collectively
form a blood group system. Blood
types are inherited and represent contributions from both
parents. A total of 32 human blood group systems are now recognized by the International Society of Blood
Transfusion (ISBT). The
two most important ones are ABO and
the RhD antigen; they determine someone's
blood type (A, B, AB and O, with + and - denoting RhD status).
Many pregnant women carry a fetus with a blood type different from their
own, and the mother can form antibodies against fetal RBCs. Sometimes these
maternal antibodies are a small
immunoglobulin, which can cross the placenta and causehemolysis of fetal RBCs, which in turn can lead
to hemolytic disease of the newborn called erythroblastosis fetalis, an
illness of low fetal blood counts that ranges from mild to severe.
Sometimes this is lethal for the fetus; in these cases it is calledhydrops
fetalis.
A blood type (also called a blood group) is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of red blood
cells (RBCs). These
antigens may be proteins, carbohydrates, glycoproteins,
orglycolipids,
depending on the blood group system. Some of these antigens are also present on
the surface of other types of cells of
various tissues.
Several of these red blood cell surface antigens can stem from one allele (or very closely linked genes) and collectively
form a blood group system. Blood
types are inherited and represent contributions from both
parents. A total of 32 human blood group systems are now recognized by the International Society of Blood
Transfusion (ISBT). The two most important ones are ABO and
the RhD antigen; they determine someone's
blood type (A, B, AB and O, with + and - denoting RhD status).
Many pregnant women
carry a fetus with a blood type different from
their own, and the mother can form antibodies against fetal RBCs. Sometimes these maternal
antibodies are IgG, a small immunoglobulin, which can
cross the placenta and cause hemolysis of fetal RBCs, which in turn can lead to hemolytic
disease of the newborn called
erythroblastos is fetalis, an illness of low fetal blood counts that
ranges from mild to severe. Sometimes this is lethal for the fetus; in these
cases it is called hydrops fetalis.
Plant Support System
Plant Support System
A plant is any organism in the kingdom Plantae. Kingdoms are
the main divisions into which scientists classify all living things on Earth. The other kingdoms
are: Monera (single-celled organisms without nuclei), Protista (single-celled
organisms with a nucleus), Fungi, and Animalia (animals). The scientific study
of plants is called botany.
A general definition of a plant is any organism that
contains chlorophyll (a green pigment contained in a specialized cell called a
chloroplast) and can manufacture its own food. Another characteristic of plants
is that their rigid cell walls are composed mainly of cellulose, a complex
carbohydrate that is insoluble (cannot be dissolved) in water. Because of the vast
number of plants that exist, cellulose is the most abundant organic compound on
Earth. Biologists have identified about 500,000 species of plants, although
there are many undiscovered species
, especially in tropical rain forests.
Plant structure
Those plants that produce seeds are the dominant and most
studied group of plants on the planet. The leaves of these plants are all
covered with a cuticle, a waxy layer that inhibits water loss. The leaves have
stomata, microscopic pores, that open during the day to take in carbon dioxide
and release oxygen during photosynthesis (process by which sunlight is used to
form carbohydrates from carbon dioxide and water, releasing oxygen as a
by-product).
Plant development
As a plant grows, it undergoes developmental changes. Most
plants continually produce new sets of organs, such as leaves, flowers, and
fruits. In contrast, animals typically develop their organs only once and these
organs merely increase in size as the animal grows.
A plant begins its life as a seed. Various environmental
cues such as sunlight, temperature changes, and the presence of nutrients
signal a seed to germinate (grow). During early germination, the young seedling
depends upon nutrients stored within the seed itself for growth. As the seedling
grows, it begins to produce chlorophyll and turn green. Most plants become
green only when exposed to sunlight because the production of chlorophyll is
light-induced.
meristem is a special tissue that contains actively growing
and dividing cells. Apical meristems are at the tips of shoots and roots and
are responsible for elongation of a plant. Lateral meristems are located along
the outer sides of the stem of a plant and are responsible for thickening of
the plant.
Plant Diseases
Plant diseases can be infectious (transmitted from plant to
plant) or noninfectious. Noninfectious diseases are usually referred to as
disorders. Common plant disorders are caused by a shortage of plant nutrients,
by waterlogged or polluted soil, and by polluted air. Too little (or too much)
water or improper nutrition can cause plants to grow poorly. Plants can also be
stressed by weather that is too hot or too cold, by too little or too much
light, and by heavy winds. Pollution from automobiles and industry and the
excessive use of herbicides (to kill weeds) can also cause noninfectious plant
disorders.
Infectious plant diseases are caused by living
microorganisms that infect a plant and rob it of nutrients. Bacteria, fungi,
and viruses are the living agents that cause plant diseases. None of these
microorganisms are visible to the naked eye, but the diseases they cause can be
detected by the symptoms of wilting, yellowing, stunting, and abnormal growth
patterns.
Some plant diseases are caused by rod-shaped bacteria. The
bacteria enter the plant through natural openings, like the stomata of the
leaves, or through wounds in the plant tissue. Once inside, the bacteria plug
up the plant's vascular system and cause the plant to wilt. Other common
symptoms of bacterial disease include rotting and swollen plant tissues.
Bacteria can be spread by water, insects, infected soil, or contaminated tools.
About 80 percent of plant diseases can be traced to fungi,
which can grow on living or dead plant tissue. They can penetrate plant tissue
or grow on the plant's surface. Fungal spores, which act like seeds, are spread
by wind, water, soil, and animals to other plants. Warm, humid conditions
promote fungal growth.
Viruses are the hardest pathogens (disease-causing
organisms) to control. Destroying the infected plants to prevent spreading to
healthy plants is usually the best control method. While more than 300 plant
viruses have been identified, new strains continually appear because these
organisms are capable of mutating (changing their genetic makeup). Viruses are
spread by contaminated seeds and sucking insects (aphids, leafhoppers, trips)
that act as carriers of the virus. The symptoms of viral infection include
yellowing, stunted growth in some part of the plant. Leaf rolls and narrow leaf
growth are other indications of viral infection. The mosaic viruses can infect
many plants. Plants infected with this virus have mottled or streaked leaves.
Genetic Engineering
Genetic Engineering
Genetic engineering, also called genetic modification, is the direct manipulation of an organism's genome using biotechnology. New DNA may be inserted in the host genome by first isolating and copying the genetic material of interest using molecular cloning methods to generate a DNA sequence, or by synthesizing the DNA, and then inserting this construct into the host organism. Genes may be removed, or "knocked out", using a nuclease. Gene targeting is a different technique that homologous recombination to change an endogenous gene, and can be used to delete a gene, remove exons, add a gene, or introduce point mutations.
An organism
that is generated through genetic engineering is considered to be agenetically modified organism (GMO).
The first GMOs were bacteria in 1973 and GM mice were generated in 1974. Insulin-producing bacteria were commercialized in 1982 and
genetically modified food has been sold since 1994. Glofish, the first GMO designed as a pet, was first sold in
the United States December in 2003.
Genetic
engineering techniques have been applied in numerous fields including research,
agriculture, industrial biotechnology, and medicine. Enzymes used in laundry
detergent and medicines such as insulin and human growth hormone are now
manufactured in GM cells, experimental GM cell lines and GM animals such as
mice orzebrafish are being used for research purposes, and genetically modified crops have
been commercialized.
Tuesday, 15 April 2014
KIDNEY
Each kidney is surrounded by a renal cortex and a renal medulla.
The functional units of the kidneys are the nephrons. The
nephrons consist of a coiled renal tubule and a vascular network of peritubular
capillaries to filter waste, macromolecules and ions from the blood and form
the urine. Each kidney consists of approximately 1 million nephrons.
The kidneys receive their blood supply from the renal
arteries, which are fed from the abdominal aorta.
The main functions of the kidney are:
· Elimination
of waste products (e.g. urea, creatinine) and excess body water
· Homeostatic
functions such as:
o regulation of electrolyte
balance
o maintenance of acid-base balance
o regulation of blood pressure
· Production
of hormones e.g. erythropoetin, renin, calcitriol
HUMAN HEART
HUMAN HEART
The heart is
a hollow muscular organ that pumps blood throughout
the blood vessels to various parts of the
body by repeated, rhythmic contractions.[1] It
is found in all animals with a circulatory system, which
includes the vertebrates.[2]
The
adjective cardiac means "related to the heart" and comes
from the Greek καρδιά, kardia,
for "heart". Cardiology is themedical speciality that
deals with cardiac diseases and
abnormalities.
The
vertebrate heart is principally composed of cardiac muscleand connective tissue. Cardiac muscle is an involuntary striated
muscle tissue specific to the heart and is responsible for the heart's ability
to pump blood.
The
average human heart, beating at 72 beats per minute, will beat approximately
2.5 billion times during an average 66 year lifespan, and pumps approximately
4.7-5.7 litres of blood per minute. It weighs approximately 250 to 300 grams (9
to 11 oz) in females and 300 to 350 grams (11 to 12 oz) in males.[3]
The adult
human heart has a mass of between 250 and 350 grams and is about the size
of a fist.[5] It is located anteriorto the vertebral
column and posterior to
the sternum.[6]
It is
enclosed in a double-walled sac called the pericardium. The pericardium's outer wall is called the
parietal pericardium and the inner one the visceral pericardium. Between them
there is some pericardial fluid which functions to permit the inner and outer
walls to slide easily over one another with the heart movements. Outside the
parietal pericardium is a fibrous layer called the fibrous pericardium which
is attached to the mediastinal fascia.[7] This
sac protects the heart and anchors it to the surrounding structures.
The outer
wall of the human heart is composed of three layers; the outer layer is called
the epicardium, or visceral pericardium since it is also the inner
wall of the pericardium. The middle layer is called the myocardium and is composed of contractile cardiac muscle.
The inner layer is called the endocardium and is in contact with the blood that the
heart pumps.[8] Also, it merges with the inner lining (endothelium) of blood vessels and covers heart valves.[9]
The human
heart has four chambers, two superior atria and
two inferior ventricles.
The atria are the receiving chambers and the ventricles are the discharging
chambers. During each cardiac cycle, the atria contract first,
forcing blood that has entered them into their respective ventricles, then the
ventricles contract, forcing blood out of the heart. The pathway of the blood
consists of a pulmonary circuit and a systemic circuit[10] which
function simultaneously. Deoxygenated blood from the body flows via the vena cava into the right atrium, which pumps it through
the tricuspid valve into
the right ventricle, whose
subsequent contraction forces it out through the pulmonary valve into the pulmonary arteries leading to the lungs.
Meanwhile, oxygenated blood returns from the lungs through the pulmonary veins into the left atrium, which pumps it through the mitral valve into the left ventricle, whose subsequent strong contraction forces it
out through the aortic valve to the aorta leading
to the systemic circulation.[11][12]
Saturday, 12 April 2014
Deoxyribonucleic acid (DNA)
DNA
Deoxyribonucleic
acid (DNA) is a molecule that encodes the genetic instructions
used in the development and functioning of all known living organisms and
many viruses.
DNA is a nucleic acid; alongside proteins andcarbohydrates,
nucleic acids compose the three major macromolecules essential
for all known forms of life.
Most DNA molecules consist of two biopolymer strands
coiled around each other to form a double helix. The two DNA strands are
known as polynucleotides since they are composed of simpler units called nucleotides.
Each nucleotide is composed of a nitrogen-containing nucleobase—either guanine (G), adenine (A), thymine (T),
or cytosine (C)—as
well as amonosaccharide sugar called deoxyribose and
a phosphate group. The nucleotides are joined to
one another in a chain by covalent bonds between
the sugar of one nucleotide and the phosphate of the next, resulting in an
alternating sugar-phosphate backbone. According to base pairing rules
(A with T and C with G), hydrogen bonds bind
the nitrogenous bases of the two separate polynucleotide strands to make
double-stranded DNA.
DNA is
well-suited for biological information storage.
The DNA backbone is resistant to cleavage, and both strands of the
double-stranded structure store the same biological information. Biological
information is replicated as the two strands are separated. A significant
portion of DNA (more than 98% for humans) is non-coding,
meaning that these sections do not serve a function of encoding proteins.
HUMAN BRAIN STRUCTURE
HUMAN BRAIN
The human
brain has the same general structure as the brains of
other mammals, but has a more developed cortex than any other. Large
animals such as whales and elephants have larger brains in absolute terms, but
when measured using the encephalization quotient which
compensates for body size, the human brain is almost twice as large as the
brain of the bottlenose dolphin, and
three times as large as the brain of a chimpanzee. Much of the expansion comes from the part of the
brain called the cerebral cortex,
especially the frontal lobes, which are associated
with executive functions such
as self-control, planning, reasoning, and abstract thought. The portion of the cerebral cortex devoted
to vision is also greatly enlarged in humans.
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