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What are the sizes of the cells that make up human hair?

What are the sizes of the cells that make up human hair?



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The question is in the title, but I'll explain why the question arose. I'm curious about the rates that various cells in the body divide, and have found various information relating to this, but nowhere can I find how often the cells divide in hair follicles (only that hair grows about 1 cm per 28 days, and that hair matrix epithelial cells divide very rapidly, which results in chemo patients' hair falling out). I figure that I can calculate a back-of-the envelope answer if I know the average size of hair cells. For example if they are 10 $mu$m, and hair grows 1 cm per 28 days, then I would estimate that the relevant cell turnover time in the follicle is on the order of 1.5 per hour, assuming that the cellular division leading to the outward growth of the hair proceeds in a serial fashion. This sounds like a roughly plausible estimate, since it is significantly faster than the turnover of other cells in the human body with a high turnover (like stomach or blood neutrophils) which have a turnover of a few days.

In any case I would appreciate any insight, whether the size of hair follicle matrix epithelial cells or the cellular turnover rate in the follicle during the anagen phase.


What Is Human Hair Made Of?

Even though hair comes in many colors and textures, it is all made of the same materials. The main ingredient of human hair is a protein called keratin, which is also found in human skin, teeth, fingernails and toenails. Hair also includes oils for texture and a chemical called melanin.


Cell Size and Scale

This simple interactive from the University of Utah's Genetic Science Learning Center gives you the opportunity to see how various small things compare to one another. Starting with a Times 12-point font and a coffee bean, scroll along to see how much larger they are than a grain of salt, a human egg, an antibody, and, finally, a carbon atom. Also, included are some reference materials about various ways to measure the size of small things&mdashfrom meters all the way down to picometers (10 -12 m)&mdashand about how such small things can best be viewed.

Going Further

This resource is so simple to use and understand that it works well in a variety of settings. Teachers can use it as a starting point for beginning to talk about cells and the building blocks of all living things or to assess students' knowledge about the relative size of various microscopic cells and organisms. It also gives students a visual reference for some of the various structures that may be covered in a biology class. Additionally, it could be tied into a conversation about the role that microscopes have played in our understanding of things that cannot be viewed unaided by the human eye.

Finally, teachers also might use this as an exercise in mathematics to cover the difference in powers of ten (e.g., A paramecium is 210 x 60&mum, while an antibody is 12nm. Which is bigger? By how much?)

Additional suggestions for incorporating this resource into the classroom can be found by clicking on the Teacher Resources & Lesson Plans button.


Materials and Methods

Preparation of hair samples

This research was approved by the Hamilton Integrated Research Ethics Board (HIREB) under approval number 14-474-T. Written consent was obtained from all participating individuals. Scalp hair samples were gathered from 12 adults of various age, gender, ethnicities, hair colour and hair curvature. It is of interest to note that there are 3 pairs of study participants with genetic relations including a father and daughter, fraternal twins and identical twins. Characteristics of the samples are listed in Table 1 .

Table 1

The individuals include men and women and hair of different appearance, such as thickness, colour and waviness, and also genetically related hair samples from a father and daughter, a pair of identical and a pair of fraternal twins. Labeling agrees with the data shown in Fig. 1 .

SubjectGenderDiameter(µm) ± SDColourAppearanceSpecial comment
1F30 ± 3light blondestraightdaughter
2M49 ± 5brown/greycurlyfather
3F74 ± 7blackwavy
4M50 ± 5light browncurly
5F49 ± 5blondecurly
6F43 ± 4light brownstraight
7F61 ± 6light brownwavy
8F49 ± 5blackwavy
9F31 ± 3blondewavyidentical twin
10F66 ± 7blackstraightfraternal twin
11F69 ± 7blackstraightfraternal twin
12F48 ± 5blondecurledidentical twin

The hair samples gathered were cut into strands around 3 cm long. Care was taken to not stretch or deform the hair strands during this process. For each subject, around 10 strands were taped onto a flexible cardboard apparatus as shown in Fig. 2 . The cut-out at the middle of the apparatus is where scattering occurs on the hair sample. The cardboard apparatus is then mounted vertically onto the loading plate of the Biological Large Angle Diffraction Experiment (BLADE) using sticky putty as shown in Fig. 2 . All hair samples were measured at room temperature and humidity of 22 ଌ and 50% RH.

The cardboard apparatus is mounted vertically onto the loading plate of the Biological Large Angle Diffraction Experiment (BLADE) using sticky putty.

X-ray diffraction experiment

X-ray diffraction data was obtained using the Biological Large Angle Diffraction Experiment (BLADE) in the Laboratory for Membrane and Protein Dynamics at McMaster University. BLADE uses a 9 kW (45 kV, 200 mA) CuKα Rigaku Smartlab rotating anode at a wavelength of 1.5418 Å. Focusing multi-layer optics provided a high intensity parallel beam with monochromatic X-ray intensities up to 10 10 counts/(s × mm 2 ) at the sample position. In order to maximize the scattered intensity, the hair strands were aligned parallel to the parallel beam for maximum illumination. The slits were set such that about 15 mm of the hair strands were illuminated with a width of about 100 µm. The effect of this particular beam geometry is seen in the 2-dimensional data in Fig. 1 : while it produces a high resolution along the equator, the main beam is significantly smeared out in the qz-direction up to qz-values of about 0.5 Å -1 , limiting the maximum observable length scale to about 13 Å.

The hair strands were oriented with the long axis of the hair parallel to the vertical z-axis. The (q, qz)-range shown was determined in preliminary experiments to cover the features observable by X-ray diffraction. The measurements cover length scales from about 3� Å to study features from the coiled-coil α-keratin phase, keratin intermediate filaments in the cortex, and the membrane layer in the membrane complex. While common features can easily be identified in the 2D plots, subtle differences are visible, which are discussed in detail in the text.

The diffracted intensity was collected using a point detector. Slits and collimators were installed between X-ray optics and sample, and between sample and detector, respectively. By aligning the hair strands in the X-ray diffractometer, the molecular structure along the fibre direction and perpendicular to the fibres could be determined. We refer to these components of the total scattering vector, Q → , as qz and q, respectively, in the following. An illustration of qz and q orientations is shown in Fig. 3 . The result of an X-ray experiment is a 2-dimensional intensity map of a large area of the reciprocal space of 𢄢.5 Å 𢄡 < qz < 2.5 Å 𢄡 and 𢄢.5 Å 𢄡 < q < 2.5 Å 𢄡 . The corresponding real-space length scales are determined by d = 2π/|Q| and cover length scales from about 3 to 90 Å, incorporating typical molecular dimensions and distances for secondary protein and lipid structures.

The hair strands were oriented in the X-ray diffractometer with their long axis along qz. Two-dimensional X-ray data were measured for each specimen covering distances from about 3� Å including signals from the coiled-coil α-keratin phase, the intermediate fibrils in the cortex and from the cell membrane complex. The 2-dimensional data were integrated and converted into line scans and fit for a quantitative analysis.

Integration of the 2-dimensional data was performed using Matlab, MathWorks. By adding up the peak intensities along the qz and the q directions, 1-dimensional data along each of the two directions were produced. The qz intensity was integrated azimuthally for an angle of 25 degrees over the meridian. The q intensity was integrated azimuthally for an angle of 25 degrees over the equator, as depicted in Fig. 3 .

The fitting process is performed on both the 1-dimensional qz and the q data produced from integration. Distinguishable peaks were observed and fitted with the least numbers of Lorentzian peak functions with an exponential decay background of the form (aq b + c) in the first run. Initial Parameters were chosen based on the observed positions, widths and heights of the peaks and free to move through the entire q-range. The criterion for the final parameters was to minimize the mean square of the difference between data intensity and the fitted intensity. If the fitted intensity cannot conform to the shape of the data intensity, more peaks will be added in the following runs until a good fit is acquired. This process was repeated for all 12 subjects and performed with little or no consultation of previous fittings to minimize bias.

As for the SAXS data, Gaussian functions are used instead. We note that the use of optical components in the beam path has an impact on the shape of the observed Bragg peaks: instead of Lorentzian or Bessel peak functions, Gaussian peak profiles were found to best describe the SAXS peaks. The fitting process was the same as mentioned before: three Gaussians were fitted to the SAXS data using free-to-move parameters and an exponential decay background. However, for some subjects, the third peak was noisy and the least mean square logarithm could not reach a good fit and hence the data was fitted with two Gaussians, only.


Examples of Cell Specialization in Animals

Neurons

The central nervous system consists of glial cells and neurons. Neurons specialize in the function of transmission of signals from different parts of the body to the brain, and transmit an appropriate response from the brain to different parts of the body.

Neurons can be up to one meter in length depending on where they are present. The neurons consist of the soma, dendrites, and axons. Soma is the cellular part of neurons containing all the major cell organelles. Dendrites are the cellular extensions that receive impulses, and axons are long cable-like projections that transmit the impulse to the next neurons. The axon terminates into a synaptic junction that transmits impulses from one neuron to the next with the help of chemicals called neurotransmitters.

Smooth Muscle Cells

All involuntary functions of our body are carried out by smooth muscle cells. They form the walls of blood vessels, gastrointestinal tract, urinary tract, respiratory tract, etc. These can be classified into single-unit smooth muscle cells and multi-unit smooth muscle cells.

Single-unit muscle fibers are compactly packed together, while multi-unit muscle fibers are more loosely packed and usually intertwined with connective tissues. Single-unit smooth muscles are spindle-shaped with a prominent nucleus in the center. They contract and relax just like striated muscle fibers, but have greater elasticity. They possess proteins like myosin and actin that aid in the contraction of cells.

Red Blood Cells

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Red blood cells perform the function of carrying oxygen from the lungs to different parts of the body they also carry carbon dioxide from different parts of the body to the lungs. These are button-shaped, i.e., biconcave, and lack a nucleus as well as many other cell organelles. They possess a protein called hemoglobin that is responsible for their oxygen-carrying capacity.

Sperm Cells

These are the male reproductive cells. Mature sperm cells are haploid and motile, which fertilize the matured female reproductive cells, i.e., the ova, to produce a zygote. The sperm cells are made of the head, mid piece, and tail. The head consists of a nucleus (the haploid chromosome) and acrosome.

The nucleus fuses with the haploid female nucleus to bring about fertilization and gives rise to a diploid individual. The acrosome contains enzymes like hyaluronidase and acrosin that dissolve the outer cell membrane of the ovum and help in the release of the nucleic material. The mid piece consists of centrioles and mitochondria wrapped around the axial filament of the flagellum. The centrioles after fertilization form the centrioles of the zygote, whereas the mitochondria provides energy for the movement of the flagellum (responsible for cell motility). The flagellum moves in a whip-like manner and propels the cell forward.


Cell Expression

2.6.2 Keratin

Keratins are a separate family of fibrous structural proteins that make up the main constituents of hair, nails, and hooves of other mammals. They are produced within cells identified as keratinocytes that are sequestered to the stratum corneum layer, that outermost, regenerative layer of the skin. Tight junctions form contacts between adjacent keratinocytes which serve to make the basement membrane rather difficult to permeate. Mitosis associated with keratinocytes occurs at the basement membrane and results in the displacement of existing cells being pushed farther from it. Thus, the older the keratinocyte, the farther it is from the basement membrane and the more dehydrated it gets. Keratinocytes transform as part of this dehydration process as the mass fraction of insoluble keratin protein composing the cell continues to rise as a function of this aging process. The cells transform their shape, flatten and rupture looking nothing like the cells originally formed within the stratum corneum layer. The scrubbing action associated with using a loofah sponge in the shower or scratching the skin is a sufficient abrasive process to exfoliate these aged and transformed keratinocytes. The sloughing is removing both old cells, oils, and keratin protein in the process. While formed as a eukaryotic cell with a well-defined nucleus, as these keratinocytes age, the identification of a nucleus becomes more difficult. It is hard to call them eukaryocytes, but they clearly start out as such.

The size and molecular architecture of keratin are noted, as the size and type of the subunits are both species and site specific [12] . The identified range in molecular weight varies between 40 and 68 kDa, depending on the type of keratin subunit being expressed. In terms of structure, three basic types of keratins are produced, a so-called α form, a β form, and an irregular conformation. In terms of amino acid composition, keratins are noted for sizable amounts of cysteine that contain thiol functionality and are further capable of forming disulfide linkages. This is a good reason why the burning of hair tends to create such noxious fumes it is the formation of hydrogen sulfide that is a gaseous reaction product of the combustion.

Prior work has resolved that keratin can be represented by two different structures being produced, with different molecular architectures and different amino acid compositions. The largest compositional difference is in the amount of cysteine found, and they are fractionated into high and low sulfur keratins and they are both found in the make-up of hair, hoof, and horn, all keratin-rich tissues. Mechanically, the high sulfur (high cysteine) proteins make up the matrix of these tissues that are reinforced by low sulfur α keratins that take a more fibrous structure. In hair, the α form is most commonly associated with a relaxed state, while the β form is induced when keratin is extended or stretched in the presence of higher humidity and temperature. Example determination of the low and high sulfur keratins found in the hoof are shown in Table 2.4 .

Table 2.4 . Amino acid composition of keratin found in hoof [13] , hair [14] , fingernail [15] , and snake skin [14] The hoof is designated as high sulfur (high S) and low sulfur (low S). Only a limited direct determination of select amino acids was determined in [14]


The Structure and Function of Liver Cells

The liver is the largest gland in the body. It’s a huge organ that sits roughly in the middle of your abdomen. It is a hugely important gland that is responsible for a wide range of metabolic and chemical reactions that are vital to living. You wouldn’t live long without a functioning liver. This article will take a looks at some of the smaller, cellular structures in the liver and what those structures do.

The liver is massively complex. Because it does so many things, it must have a correspondingly complex structure, even at the cellular level. If you were to take a slice of liver tissue and look at it under a microscope, you would see a series of criss-crossed bands of tissue. This roadwork of connective tissue serves to divide the liver in to functional groups, known as “lobules”. There are thousands of lobules in a healthy adult liver.

Lobules in the liver are “fed” by a central vein. They are (very) approximately shaped like a hexagon. Note that this is a common textbook description, but biological structures rarely take on perfectly symmetrical shapes, so don’t expect all six sides to be exactly the same size.

Each of the lobules has a series of “tubes” going in and out that are called the “portal triad”. These structures help move chemicals in and out of the lobule, along with the central vein.

If we increase the magnification of our virtual microscope, we will eventually be able to see the functional cells of the liver. These cells are called hepatocytes. They are approximately shaped like little pyramids, but again, these shapes are not perfect. Hepatocytes are connected to each other by something called an “anastomosing plate”. The plates allow the hepatocytes to “communicate” with each other and to pass chemicals back and forth very efficiently.

Because hepatocytes are primarily involved in metabolism and chemical processing, you’d expect that they would be mostly filled with organelles that serve these functions. And you’d be right. While they may not have as many mitochondria as a muscle cell, they are stuffed full of Golgi aparatus and Endoplasmic retuculum (both rough and smooth). If you aren’t familiar with these terms, do a search for the basics of cellular structure. Liver cells also store a lot of lipids and fat.

Hepatocytes must be able to make contact with the blood stream. They do this in areas known as sinusoids. Also in the sinusoids are specialized “trash collector” cells known as Kupffer Cells. These cells serve to clean up junk and swallow up foreign invaders such as bacteria and viruses. They do this by literally swallowing their target. Yummy!

One of the more important functions of the liver is to make bile. Bile is a chemical that is stored in the gallbladder and is used to help your body digest fats. Bile is made in the hepatocytes and transferred to the gallbladder in a series of channels called caniliculi. These come together to form interlobular bile ducts, and ultimately a single large bile duct.

There is obviously a lot of detail in the histology of the liver that this article cannot go in to. Medical school will spend several weeks of intense lectures on the structure and function of liver cells – making it impossible to condense this information in to a small space such as this. This article should provide a basic starting point to understanding the cells of the liver and what some of them do.


What are genes and why are they important?

All living beings have genes. They exist throughout the body. Genes are a set of instructions that determine what the organism is like, its appearance, how it survives, and how it behaves in its environment.

Genes are made of a substance called deoxyribonucleic acid, or DNA. They give instructions for a living being to make molecules called proteins.

A geneticist is a person who studies genes and how they can be targeted to improve aspects of life. Genetic engineering can provide a range of benefits for people, for example, increasing the productivity of food plants or preventing diseases in humans.

Share on Pinterest Genes are responsible for all aspects of life.

Genes are a section of DNA that are in charge of different functions like making proteins. Long strands of DNA with lots of genes make up chromosomes. DNA molecules are found in chromosomes. Chromosomes are located inside of the nucleus of cells.

Each chromosome is one long single molecule of DNA. This DNA contains important genetic information.

Chromosomes have a unique structure, which helps to keep the DNA tightly wrapped around the proteins called histones. If the DNA molecules were not bound by the histones, they would be too long to fit inside of the cell.

Genes vary in complexity. In humans, they range in size from a few hundred DNA bases to more than 2 million bases.

Different living things have different shapes and numbers of chromosomes. Humans have 23 pairs of chromosomes, or a total of 46. A donkey has 31 pairs of chromosomes, a hedgehog has 44, and a fruit fly has just 4.

DNA contains the biological instructions that make each species unique.

DNA is passed from adult organisms to their offspring during reproduction. The building blocks of DNA are called nucleotides. Nucleotides have three parts: A phosphate group, a sugar group and one of four types of nitrogen bases.

A gene consists of a long combination of four different nucleotide bases, or chemicals. There are many possible combinations.

Different combinations of the letters ACGT give people different characteristics. For example, a person with the combination ATCGTT may have blue eyes, while somebody with the combination ATCGCT may have brown eyes.

To recap in more detail:

Genes carry the codes ACGT. Each person has thousands of genes. They are like a computer program, and they make the individual what they are.

A gene is a tiny section of a long DNA double helix molecule, which consists of a linear sequence of base pairs. A gene is any section along the DNA with instructions encoded that allow a cell to produce a specific product – usually a protein, such as an enzyme – that triggers one precise action.

DNA is the chemical that appears in strands. Every cell in a person’s body has the same DNA, but each person’s DNA is different. This is what makes each person unique.

DNA is made up of two long-paired strands spiraled into the famous double helix. Each strand contains millions of chemical building blocks called bases.

Genes decide almost everything about a living being. One or more genes can affect a specific trait. Genes may interact with an individual’s environment too and change what the gene makes.

Genes affect hundreds of internal and external factors, such as whether a person will get a particular color of eyes or what diseases they may develop.

Some diseases, such as sickle-cell anemia and Huntington’s disease, are inherited, and these are also affected by genes.

A gene is a basic unit of heredity in a living organism. Genes come from our parents. We may inherit our physical traits and the likelihood of getting certain diseases and conditions from a parent.

Genes contain the data needed to build and maintain cells and pass genetic information to offspring.

Each cell contains two sets of chromosomes: One set comes from the mother and the other comes from the father. The male sperm and the female egg carry a single set of 23 chromosomes each, including 22 autosomes plus an X or Y sex chromosome.

A female inherits an X chromosome from each parent, but a male inherits an X chromosome from their mother and a Y chromosome from their father.

The Human Genome Project (HGP) is a major scientific research project. It is the largest single research activity ever carried out in modern science.

It aims to determine the sequence of the chemical pairs that make up human DNA and to identify and map the 20,000 to 25,000 or so genes that make up the human genome.

The project was started in 1990 by a group of international researchers, the United States’ National Institutes of Health (NIH) and the Department of Energy.

The goal was to sequence 3 billion letters, or base pairs, in the human genome, that make up the complete set of DNA in the human body.

By doing this, the scientists hoped to provide researchers with powerful tools, not only to understand the genetic factors in human disease, but also to open the door for new strategies for diagnosis, treatment, and prevention.

The HGP was completed in 2003, and all the data generated is available for free access on the internet. Apart from humans, the HGP also looked at other organisms and animals, such as the fruit fly and E. coli.

Over three billion nucleotide combinations, or combinations of ACGT, have been found in the human genome, or the collection of genetic features that can make up the human body.

Mapping the human genome brings scientists closer to developing effective treatments for hundreds of diseases.

The project has fueled the discovery of more than 1,800 disease genes. This has made it easier for researchers to find a gene that is suspected of causing an inherited disease in a matter of days. Before this research was carried out, it could have taken years to find the gene.

Genetic tests can show an individual whether they have a genetic risk for a specific disease. The results can help healthcare professionals diagnose conditions.

The HGP is expected to speed up progress in medicine, but there is still much to learn, especially regarding how genes behave and how they can be used in treatment. At least 350 biotechnology-based products are currently in clinical trials.

In 2005, the HapMap, a catalog of common genetic variation or haplotypes in the human genome, was created. This data has helped to speed up the search for the genes involved in common human diseases.

In recent years, geneticists have found another layer of heritable genetic data that is not held in the genome, but in the “epigenome,” a group of chemical compounds that can tell the genome what to do.

In the body, DNA holds the instructions for building proteins, and these proteins are responsible for a number of functions in a cell.

The epigenome is made up of chemical compounds and proteins that can attach to DNA and direct a variety of actions. These actions include turning genes on and off. This can control the production of proteins in particular cells.

Gene switches can turn genes on and off at different times and for different lengths of time.

Recently, scientists have discovered genetic switches that increase the lifespan and boost fitness in worms. They believe these could be linked to an increased lifespan in mammals.

The genetic switches that they have discovered involve enzymes that are ramped up after mild stress during early development.

This increase in enzyme production continues to affect the expression of genes throughout the animal’s life.

This could lead to a breakthrough in the goal to develop drugs that can flip these switches to improve human metabolic function and increase longevity.

Gene marking

When epigenomic compounds attach themselves to DNA in the cell and modify the function, they are said to have “marked” the genome.

The marks do not change the sequence of the DNA, but they do change the way cells use the DNA’s instructions.

The marks can be passed on from cell to cell as they divide, and they can even be passed from one generation to the next.

Specialized cells can control many functions in the body. For example, specialized cells in red blood cells make proteins that carry oxygen from air to the rest of the body. The epigenome controls many of these changes within the genome.

The chemical tags on the DNA and histones can become rearranged as the specialized cells and the epigenome change throughout a person’s lifetime.

Lifestyle and environmental factors such as smoking, diet and infectious diseases can bring about changes in the epigenome. They can expose a person to pressures that prompt chemical responses.

These responses can lead to direct changes in the epigenome, and some of these changes can be damaging. Some human diseases are due to malfunctions in the proteins that “read” and “write” epigenomic marks.

Some of these changes are linked to the development of disease.

Cancer can result from changes in the genome, the epigenome or both. Changes in the epigenome can switch on or off the genes that are involved in cell growth or the immune response. These changes can cause uncontrolled growth, a feature of cancer, or a failure of the immune system to destroy tumors.

Researchers in The Cancer Genome Atlas (TCGA) network are comparing the genomes and epigenomes of normal cells with those of cancer cells in the hope of compiling a current and complete list of possible epigenomic changes that can lead to cancer.

Researchers in epigenomics are focused on trying to chart the locations and understand the functions of all the chemical tags that mark the genome. This information may lead to a better understanding of the human body and knowledge of ways to improve human health.

Gene therapy

In gene therapy, genes are inserted into a patient’s cells and tissues to treat a disease, usually a hereditary disease. Gene therapy uses sections of DNA to treat or prevent disease. This science is still in its early stages, but there has been some success.

For example, in 2016, scientists reported that they had managed to improve the eyesight of 3 adult patients with congenital blindness by using gene therapy.

In 2017, a reproductive endocrinologist, named John Zhang, and a team at the New Hope Fertility Center in New York used a technique called mitochondrial replacement therapy in a revolutionary way.

They announced the birth of a child to a mother carrying a fatal genetic defect. Researchers combined DNA from two women and one man to bypass the defect.

The result was a healthy baby boy with three genetic parents. This type of research is still in the early stages, and much is still unknown, but results look promising.

Scientists are looking at different ways of treating cancer using gene therapy. Experimental gene therapy may use patients’ own blood cells to kills cancer cells. In one study, 82 percent of patients had their cancer shrink by at least half at some point during treatment.

Gene testing to predict cancer

Another use of genetic information is to help predict who is likely to develop a disease, for example, early-onset Alzheimer’s disease and breast cancer.

Women with the BRCA1 gene have a significantly higher chance of developing breast cancer. A woman can have a test to find out whether she carries that gene. BRCA1 carriers have a 50 percent chance of passing the anomaly to each of their children.

Genetic tests for personalized therapy

Scientists say that one day we will be able to test a patient to find out which specific medicines are best for them, depending on their genetic makeup. Some medicines work well for some patients, but not for others. Gene therapy is still a growing science, but in time, it may become a viable medical treatment.


Dermis

The layer beneath the epidermis is the dermis, the thickest layer of the skin. The main cells in the dermis are fibroblasts, which generate connective tissue as well as the extracellular matrix that exists between the epidermis and the dermis. The dermis also contains specialized cells that help regulate temperature, fight infection, store water, and supply blood and nutrients to the skin. Other specialized cells of the dermis help in the detection of sensations and give strength and flexibility to the skin. Components of the dermis include:

  • Blood vessels: Transport oxygen and nutrients to the skin and remove waste products. These vessels also transport vitamin D from the skin to the body.
  • Lymph vessels: Supply lymph (milky fluid containing white blood cells of the immune system) to skin tissue to fight microbes.
  • Sweat glands: Regulate body temperature by transporting water to the skin's surface where it can evaporate to cool down the skin.
  • Sebaceous (oil) glands: Secrete oil that helps waterproof the skin and protect against microbe build-up. These glands are attached to hair follicles.
  • Hair follicles: Tube-shaped cavities that enclose the hair root and provide nourishment to the hair.
  • Sensory receptors: Nerve endings that transmit sensations such as touch, pain, and heat intensity to the brain.
  • Collagen: Generated from dermal fibroblasts, this tough structural protein holds muscles and organs in place and gives strength and form to body tissues.
  • Elastin: Generated from dermal fibroblasts, this rubbery protein provides elasticity and helps make the skin stretchable. It is also found in ligaments, organs, muscles, and artery walls.

What is Microbiology? Importance, Types, and History

What is Microbiology? Importance, Types, and History What is Microbiology? Microbiology is one of the branches that make up biology and focuses on the study of microorganisms. It is dedicated to its classification, description, distribution, and analysis of its ways of life and functioning. In the case of pathogenic microorganisms, microbiology also studies their form of … Read more


Watch the video: Cell and molecular Size Comparison (August 2022).