Human
Cell
- Cell is the smallest part of living beings. The body is made up of millions of tiny cells. These are the building blocks of the body. A single is too small to be seen with a naked eye.
- A microscope is needed to see the single cell. There are different kinds of cell. Cells differ in their shapes and functions. For example, skin cells, muscles are made up of muscle cells, bones, teeth, and mails are made up of different jobs. Cell wall, cell membrane, nucleus and cytoplasm are the basic parts of the cell.
Types of Human Cell:
Red Blood Cells: These are blood cells which form most of the part of our blood. These cells carry food and oxygen to other body parts to sustain life.
Liver Cells: Liver cells perform many functions like like glucose breakdown and protein and carbohydrate synthesis. They are found in liver which is one of the major organs of human body.
Skin Cells
Epithelial cells, or skin cells, divide
and reproduce much more quickly than some other types of cells. Skin cells form
a protective barrier between delicate organs and the outside world.
Not only do skin cells provide a means to contain all the various
inner workings of the human body, but they also help to regulate body
temperature, and to keep out infection.
Skin cells are square in shape and flat.
Human skin itself is composed of layers of cells: the epidermis, the dermis, and the
hypodermis. The epidermis is the outermost, visible layer of skin which
provides waterproof protection against foreign substances. The dermis, the
layer beneath the epidermis, is a thick layer of tissue which contains glands,
nerve endings, hair follicles, and blood vessels.
Muscle Cells
Human muscles contain hundreds of
thousands of muscle cells and each muscle cell performs a function specific to
the type of muscle of which it is a part. Individual muscle cells, or muscle
fibers, are composed of myofibrils - cylindrical structures which contain both
thick and thin filaments.
The overlapping of these filaments creates cellular units called
sarcomeres and when muscle fibers and sarcomeres are grouped together, they
form what are called fascicles.
These bundles, or fascicles, are then grouped together to form
human muscle.
There are three different types of muscles within the human body:
skeletal, cardiac, and smooth muscle. Skeletal muscle is anchored to bone
by tendons and can be used to facilitate motion. Cardiac muscle is similar in
structure to skeletal muscle, but is only present in the heart.
Smooth muscle, also called involuntary muscle, makes up the walls
of organs and other bodily structures like the esophagus and blood vessels.
Nerve Cells
Nerve cells, or neurons, are electrically
charged cells that transmit information between different parts of the body by
means of electrical and chemical signals.
Neurons make up
the body's nervous system, which
includes the brain and spinal cord by forming networks of nerve cells through
which signals, or synapses, can be sent.
There are several specific types of neurons including the sensory
neurons and motor neurons.
Sensory neurons respond to stimuli affecting the cells of sensory
organs, like the eyes, and then send signals to the brain.
Motor neurons transmit signals from the brain and spinal cord to
other parts of the body to affect the glands and to stimulate muscle
contractions which facilitate movement.
Stem Cells
Stem cells are known for their self-renewing properties and for
their capacity to differentiate into many specialized cell types.
Recent scientific developments have led to the manipulation of
stem cells to produce viable tissues through the means of cell culture. Stem
cells are found in high concentration in amniotic fluid, umbilical cord blood,
and bone marrow.
These cells can be used to treat leukemia and may, in the future,
provide insight into a cure for Parkinson's disease, spinal cord injuries, and
other types of cancer.
Gametes
Gametes, or sex cells, exist in two
varieties within the body: sperm and eggs. These cells are formed by the process
of meiosis within the ovaries and testes.
The union of these two types of cells initiates the process of
reproduction and the formation of a new individual.
Both male (sperm)
and female (egg) sex cells contain genetic material (called DNA) and the combination
of the genetic material results in an individual genetically different from the
parents.
How Cells Work Together in the Human Body
Although there are
many different types of cells in the human body and their uses are all very
different, every cell works together with every other cell to make the body
function.
All cells in the human body are encased in a cell membrane which
not only protects the contents of the cell but also contains receptors which
help to identify one cell to another.
The different cells in the human body perform different functions,
each one essential to the overall health of the body.
Some cells produce substances which the body needs to survive -
substances like insulin - and others are bound together to create bones,
muscles, and organs. Nerve cells allow for communication between all the different
parts of the body and help to regulate its many functions.
If the function of even one type of cell is interrupted, the
entire body can be affected. Though they may be small, cells are what make up
the human body and what make it work.
From nerve cells and muscle cells to stem cells and sex cells,
there are myriad types of cells in the human body and their uses are just as
variegated.
No one type of cell is more important than the other, because
without all of the different types of cells the human body would not be able to
function.
It is because of the hundreds of different types of cells working
together that our lungs are able to take in oxygen and that our brain can
communicate with the different parts of our body. Cells are the fundamental units
that make up the human body and they are extremely important.
Facts of cells
1.
Cells
are too small to be seen without magnification.
Cells range in size from 1 to 100 micrometers. The study of cells, also called cell biology, would not have been possible without the invention of the microscope. With the advance microscopes of today such as the Scanning Electron Microscope and Transmission Electron Microscope, cell biologists are able to obtain detailed images of the smallest of cell structures.
2. There are two primary types of cells.
Eukaryotic and prokaryotic cells are the two main types of cells. Eukaryotic cells are called so because they have a true nucleus. Animals, plants, fungi and protists are examples of organisms that are composed of eukaryotic cells. Prokaryotes include bacteria and archaeans.
3. Prokaryotic single-celled organisms were the earliest and most primitive forms of life on earth.
Prokaryotes can live in environments that would be deadly to most other organisms. They are able to live and thrive in various extreme habitats.Archaeans for example, live in areas such as hydrothermal vents, hot springs, swamps, wetlands, and even animal intestines.
4. There are more bacterial cells in the body than human cells.
Scientists have estimated that about 95% of all the cells in the body are bacteria. The vast majority of these microbes can be found within the digetive tract.
5. Cells contain genetic material.
Cells contain DNA (deoxyribonucleic acid), the genetic information necessary for directing cellular activities. DNA is a type of molecule known as a nucleic acid. In prokaryotic cells, the single bacterial DNA molecule is not separated from the rest of the cell but coiled up in a region of the cytoplasm called the nucleoid region. In eukaryotic cells, DNA molecules are located within the cell's nucleus. DNA and proteins are the major components of chromosomes. Human cells contain 23 pairs of chromosomes (for a total of 46). There are 22 pairs of autosomes (non-sex chromosomes) and one pair of sex chromosomes. The X and Y sex chromosomes determine gender.
6. Cells contain structures called organelles which carry out specific functions.
Organelles have a wide range of responsibilities within a cell that include everything from providing energy to producing hormones and enzymes. Eukaryotic cells contain several types of organelles, while prokaryotic cells contain a few organelles (ribosomes) and none that are bound by a membrane. There are also differences between the kinds of organelles found within different eukaryotic cell types. Plant cells for example, contain structures such as a cell wall and chloroplasts that are not found in animal cells. Other examples of organelles include:
·
Nucleus
·
Mitochondria
·
Endoplasmic Reticulum
·
Golgi Complex
·
Ribosomes
7. Different types of cells reproduce through different
methods.
Most prokaryotic cells reproduce by a process called binary fission. This is a type of cloning process in which two identical cells are derived from a single cell. Eukaryotic organisms have a similar type of reproductive method known as mitosis. Some eukaryotes also have the ability to reproduce sexually, which involves the fusion of sex cells or gametes. Gametes are produced by a process called meiosis.
8. Groups of similar cells form tissues.
Tissues are groups of cells with both a shared structure and function. Cells that make up animal tissues are sometimes woven together with extracellular fibers and are occasionally held together by a sticky substance that coats the cells. Different types of tissues can also be arranged together to form organs. Groups of organs can in turn form organ systems.
9. Cells have varying life spans.
Cells within the human body have different life spans based on the type and function of the cell. They can live anywhere from a few days to a year. Certain cells of the digestive tract live for only a few days, while some immune system cells can live for up to six weeks. Pancreatic cells can live for as long as a year.
10. Cells commit suicide.
When a cell becomes damaged or undergoes some type of infection, it will self destruct by a process called apoptosis. Apoptosis works to ensure proper development and to keep the body's natural process of mitosis in check. A cell's inability to undergo apoptosis can result in the development of cancer.
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