Cells Regeneration: 4 Types of tissue in the Human Body

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A Human body consists of 4 types of tissue. These 4 types of tissue make up our human body. Namely: Epithelial, Connective, Muscular, and nervous are the 4 types of tissue. We will cover all 4 types of tissue and Cell regeneration concepts in detail.

This content helps you to remember the basic terms related to physiology. Learning objectives of this article is,

  • Cells and structure of a cell
  • The main type of cell
  • differences between a prokaryotic and eukaryotic cell with example 
  • What is cell regeneration and how it works?
  • Regeneration in human and types of regeneration 
  • Tissue and what are 4 types of tissue?
  • Difference between pluripotent and totipotent.

Cell Structure

Cells are the building blocks of all living organisms. The cells give structure to the body and it takes nutrients from food which we eat; these nutrients convert in the form of energy and carry specialized functions. Cells consist of following major parts, these are

  • Cytoplasm: It is made up of a jelly-like fluid (named as cytosol) and it surrounds the nucleus.
  • Cytoskeleton: Cytoskeleton is a long fibers network that helps to make cell structure. It gives a track system that directs the movement of organelles.
  • Endoplasmic reticulum: ER helps the process of molecules which are created by the cell. And transports the molecules inside or outside the cell.
  • Golgi apparatus: It is processed by endoplasmic reticulum to be transported out of the cell.
  • Lysosomes and peroxisome; These are recycling centers of the cell. They digest foreign particles and prevent the cells from toxic substances.
  • Mitochondria: Mitochondria also known as the powerhouse of cells. This organelle has its own genetic material that separates the DNA and makes copies of themselves.
  • Nucleus: Nucleus is the command center of the cell and helps to send directions to the cell. The nucleus is surrounded by a membrane and protects the DNA
  • Plasma membrane: This is the outer lining of the cell. It separates the cell from its environment.
  • Ribosomes: The ribosome floats freely in the cytoplasm.
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4 Type of cells:

Basically there are many different types of cells such as white blood cells, red blood cells, skin cells, bone cells, and bacterial cells, And each type of cells has its own particular function. Cells usually combine to form tissues and these tissues combine to form an organ.

But all bacteria, human being or any other types of organisms have two general types of cells these are,

1. Prokaryotic cells

Prokaryotic cells are simple, singular shaped cells.  The DNA of Prokaryotic cells found in central parts of cell while the dark region of cell called nucleoid.prokaryotic cells are usually smaller than eukaryotic cells and they are ranging from 0.1-5.0 um diameter, as you know the size of Prokaryotic cells is small that’s why but allows organic molecules and you’d to enter quickly and spread all over parts if body.

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2. Eukaryotic cells

Eukaryotic cells are the membrane-bounded nucleus and the component kg these membrane-bounded sacs known as an organelle.  Organelle has specialized functions. Eukaryotic cells ranged from 10-100 um in diameter. Eukaryotic cells are larger in size and it involves structural adaptation because larger cells become more difficult to acquire sufficient material and process inside the cells.

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Difference between Prokaryotic and eukaryotic cells

  • In Prokaryotic cells only one chromosome is present, while in eukaryotic cells more than one chromosome is present 
  • Prokaryotes are unicellular, eukaryotes are multicellular.
  • Lysosomes and peroxisome are absent in Prokaryotes, while both Lysosomes and peroxisome are present in eukaryotes.
  • Mitochondria is also absent in Prokaryotes, rather than absent in eukaryotes.
  • Endoplasmic reticulum, cytoskeleton and Golgi apparatus are absent in Prokaryotic cells, while these all are present in eukaryotic cells.
  • In Prokaryotes ribosomes are smaller in size while in Eukaryotes ribosomes are larger in size.
  • Chloroplasts are absent in Prokaryotes because chlorophyll is scattered in cytoplasm, while chloroplasts are present in eukaryotes.
  • Cell wall of Prokaryotes is chemically complex while the cell wall of eukaryotes is chemically simple.
  • Permeability of nuclear membrane absent in Prokaryotes, or present in eukaryotes.
  • Pili and fimbriae may be present or not in Prokaryotes but totally absent in eukaryotes.
  • Prokaryotes differ from eukaryotes in their arrangement, genes, density, structure, composition because the Prokaryotic cell lacks introns.

Example of Prokaryotes

1. Escherichia Coli

E. coli is rod shaped bacteria and mostly it’s found in the lower intestine (of warm blooded organism). Usually E. coli is harmless but some of them cause harm or food poisoning. Those E. coli which is not harmful, it is beneficial for producing vitamin K2.

2. Streptococcus Bacterium

Streptococcus bacterium is Prokaryotes and these Prokaryotes responsible for strep throat and may cause infection of the throat results in tonsils.  A division of cell in streptococcus bacteria occurs in a single axis and grows in the form of chain or pairs.Symptoms appear due to this streptococcus bacterium is fever, redness and sore throat.

3. Archaea

These Prokaryotes are capable of surviving in harsh environments and thus archaea found in geothermally active areas. Archaea lives in mud spots and is known as acidocaldarius archaebacteria.

Example of eukaryotes

1. Fungi

Fungi consist of one cell or many cells, fungi have a cell wall but this cell wall contains protein known as chitin. The chitin is found in animals but not in plants.  Example of microscopic fungi includes yeast. When we make beads, chews and wine thus cause athlete’s food.

2. Protist

Protest is one cell eukaryotes. Protists are a wide range of organisms and mostly seaweed firm groups with protest and some are not closely related. Examples of protists are paramecium and amoeba.

3. Animals

An animal includes human, arthropods, whale, fish and house cats.  These all belong to eukaryotes. Animals named as metazoans or it belongs to kingdom animalia. Animals have cell membranes but the rigid cell wall is absent. Kingdom animalia are a more mobile and active group of eukaryotes

Cell Regeneration

In science, regeneration is the process of re-establishment, rehabilitation, and growth that makes the genome (complete set of genetic material in cell and encoded the hereditary information), cell, organism, and ecosystem resilient, ecological aboutness capability of the ecosystem to maintain the normal pattern of nutrients cycle. In other words, regeneration is growth of lost tissue or organ in relation to any injury, trauma, wound or cut. Regeneration helps to heal wounds and it involves the closing of any injury or cut.  Skin is the largest organ of our body that’s why it has the ability to regenerate quickly instead of other tissues that have less capacity or might be no capacity to regenerate. Cells or tissue regenerate naturally after a specific period of time

If your tissues and cells get injured then your body shows different responses for example, after an injury or wound scars appear over a time period longer than regulation of the cell.

Role of stem cell in regeneration

Stem cells play an important role in regeneration because stem cells have the ability to renew and rehabilitate themselves so many times. Stem cells develop many different types of cells in your body. An important role of stem cells is to repair and maintain the damaged tissues. Stem cells are known as multipotent cell because they isolate adipose tissues (stored energy in the form of fat)

How Cell regeneration works?

  • According to previous research in different regenerating animals, show the strategies of various stem cells, which regenerate body parts by repairing multiple tissues, for example, muscle skin, liver.
  • Researcher of U.S.A name Peter Reddien does clarify the concept of regeneration. He regenerates planarians (flatworm) and clear the concept about, is single cell regenerate or regrow animals or not? So the answer is yes a single cell regenerates the whole animal.
  • They show planarians have pluripotent stem cells (make all types of cell) but not animals have pluripotent cells while some do not use this cell in the regeneration process. Remember, stem cells regrow or regenerate the tail of frog and limb of salamander but both have different properties from planaria stem cells. Each tissue of this animal has its own set of stem cells which make  different types of cells. In simple and clarifying words the cells do not make skin and the skin stem cell does not make muscle. The multipotent tissue is probably similar to stem cells in our bodies and that cell  regrows or regenerates tissue by using stem cells, regrowth of cell done and they stop multiplying and dividing to go back in order to Replace or renew the damage, injury and lots of tissues .

Regeneration in humans

Regeneration in humans and human body parts is regrowth of tissue or organs due to any injury. Some tissues are capable of regrowing quite readily Such as liver growth but other tissue has no capability to regenerate. As you know tissue regrows naturally after a specific time and these tissues are capable of replacing older one or damage cells into newer one. For example,

  1. Non-injured tissue: Non- injured tissue regrows within two weeks.
  2. Injured tissue: if tissue gets injured, usually shown different responses. Emergency response of this tissue is to build scar tissue to close the wounds for a longer time period. This tissue shows response and heals themselves. The human body organ that renews itself may include endometrium, liver, finger tips.
  • Recreation in human body can take place at different levels, these levels are

1. Cellular level:

As you know the morphology of cells are heterogeneous and homogeneous and always bunch together to regrow a tissue in specific structure and with their function. Example of cellular regeneration is your nerves cell or neurons. Nerve cells or neurons are effective for regeneration.

Neuron consists of dendrites (receive signals from neurons), axon (thread-like structure conducts impulses) and a cell body (spherical part of neurons which brings information) and these all work together to process the cell body’s revival and delivery of messages in all over the body.  But if your neuron gets separated from the axon (delivery of message) , the cell body remains Undamaged, so your axon has capability to close the wound and regenerate or regrow newer once and start to renew it to revive another augmentation to replace the damages.

2. Tissue level:

Most tissues in the human body are capable of displaying regeneration in retaliation to any injury or wound as general aftercare of normal tissues.  The tissue can regenerate or regrow whenever the environment in the tissue must be perfect or right. Cardiac muscle tissues do not regenerate themselves. Cells are capable of reviving themselves and regenerate energy in response to regeneration signals. Cells able to communicate and directly multiply or differentiate into normal tissue.  The signal which impedes regeneration must be regulated to enable an environment for growth and functioning like healthier tissue.

3. Molecular level:

Cells can be regenerated on a molecular level.  As you know, a cell is a functional unit if a system and thousands of molecules interrelate with each other to perform every day process (protein, DNA, carbohydrate, RNA, lipid).  The content of regulation on every cell’s providence is based on the interaction of division, for remain same and for die. Every cell readjust them to activate mechanisms of replication, and regrow themselves, division and death in retaliation to the environment.

Types of Regenerations

Basically there are two types of regeneration

1. Epimorphosis:

This type of regeneration appears in salamander limbs. This generation includes information of new parts or organs known as blastemal. Amputation is sensed by the number of somatic cells that migrate to wound and increase rate of division. The wounds blastemal forms and these blastemal cross multiple to regrow the damage and lost tissues.


Regeneration of vertebrates (limb) This regeneration involves differentiation of cells because epidermal cells form blastemal.

2. Morphallaxis

This type regeneration usually appears in hydras. The difference between these two regeneration (epimorphosis or morphallaxis), Morphallaxis not involved in formation of blastemal and not replicate themselves., instead of that existing tissues rearrange themselves and transform it into new organs.  This type of regeneration has a little growth.


Hydra grows by a budding process when hydra cuts into two, the upper part of hydra develops into foot and lower part of hydra develop into head.  The formation of head inhibits the region of the head.

What is a Tissue?

Tissues consist of groups that are structurally and functionally similar cells. Tissue absent in unicellular organisms and present in multicellular organisms. There are mainly 4 types of tissue.

4 Types of tissues

Basically tissues have four types and these are,

1. Connective tissue

Connective tissue is the most basic tissue out of 4 types of tissue in the human body. Connective tissue has a mesodermal origin and this tissue connects various types of cells. Connective tissues have seven types and these are,

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i. Areolar connective tissue

Areolar tissues nourish and pillow the epithelial tissue and the function of this tissue is to provide protection against infection, this tissue found in outer covering of the esophagus, nerves, and blood vessels.

ii. Adipose tissue

The adipose tissue is fatty tissue. The function of this tissue is to store the energy and this tissue found in the heart, eye, under the skin.

iii. Dense irregular tissue

As shown by the name these tissues are dense space and these tissues arranged randomly. The function of this tissue is to protect from injuries. This tissue found in spleen, liver, and skin (dermis layer)

iv. Dense regular tissue

This tissue works parallel to irregular tissue and they help to bind bones together. This tissue is found in tendons and ligaments.

v. Cartilages

The function of cartilage is to move bones smoothly in joints and it can cushion and deaden the loads, it also gives shape and structure. These cartilages found in the larynx, external ear,  come from bones between the ribs and sternum.

vi. Bones.

As we know bone covers half if the weight of our body and the function of bones is to provide support and structure.

vii. Blood

Bloods carry erythrocytes, platelets and leukocytes, function of blood is to transport the minerals and give nutrients to the body or regulate the hormones.

2. Epithelium tissue

Epithelial tissues are tissues that help to cover the body and line the organs of vessels.  A tissue of epithelium makes the thin layer of cells which is known as endothelium.  Epithelium tissue is closely packed to one another because of its tightly packed structure and it acts as a barrier and protects all bodily functions. It also helps to protect against microorganisms and helps in absorption, secretion and excretion of substances. The types of epithelium tissue is

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i. Simple epithelium

This tissue contains single layers of cells. Simple epithelium tissue is lining the kidney, skin, blood and lungs. Simple tissues help in diffusion and osmosis processes.

ii. Stratified tissues

Stratified tissues contain multiple layers of cells and it prevents loss of water.  Stratified tissues found in the reproductive and digestive tract.

iii. Pseudostratified tissues

This tissue appears as a stratified epithelium tissue but it’s not.  In Pseudostratified tissue, a single cell obtains a nucleus and It helps to remove the particle (unnecessary) in the lungs. This tissue is found in the respiratory tract.

3. Muscles tissue

As you know our half bodyweight is muscles, These muscles are composed of muscular tissues that are the heaviest out of 4 types of tissue. Muscular tissue is of three types. Every type of muscular tissue has a unique function and structure.

i. Skeletal muscles

Skeletal muscles help to move the bones in response to voluntary messages which come from our nervous system. This tissue is made up of long cells and named as muscle fiber, it appears as striated muscles.

ii. Smooth muscles

This type of muscles are found in hollow parts if body and thus jacked show an involuntary movement and trigger impulses which travels through our autonomic nervous system, these are found in,

a)  In wall of urinary bladder

Smooth muscles of the urinary bladder expand and relax them.

b) In alimentary canal

Smooth muscles in the wall of alimentary canal halls to swallow the food.

c) In eye

Smooth muscles help to change the shape of lenses to focus the objects.

d)  In artery wall

Smooth muscles help in the artery wall to contract and relax, also move the blood all over the body.

iii. Cardiac muscles

Cardiac or heart muscles are composed of cells known as cardiomyocytes; they have a striated appearance.  The structure of these muscles is shorter and thicker.

4. Nervous tissue

Nervous tissues are tissue of the nervous system and help to regulate and monitor the body. It carries the nerve impulses and produces signals which transmit to all bodies.  This tissue makes CNS (central nervous system) and PNS (peripheral nervous system). Nervous tissue is categorized into three types.

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i. Motor nerves

Motor nerves are responsible for sending the signal in your body. It carries impulses from the brain and this impulse helps in doing activities such as, eating,  sleeping,  drinking and walking. If this motor nerves are damaged, it may result in weakness of muscles.

ii. Sensory nerves

Sensory neurons help to generate the signals. It helps to collect information which is pain, touch and temperature. If this neuron damages, it may result in numbness, pain and loss of sensation.

iii. Autonomic nerves

Autonomic nerves are involved in the action of the heart, muscles and help to regulate involuntary function.  It further classified into

a)  Sympathetic nervous system: It is responsible for fight and flight response.

b)  Parasympathetic nervous system: It helps to control activities of digestion, excretion and secretion.

4. Cranial nerves

Basically cranial nerves are of twelve (12) types which emerge from the lower part of the brain and these nerves are.

i. Olfactory nerve: Convey messages to the brain and responsible for smell. Olfactory nerve named as CN1.

ii. Optic nerve: CN2 connects eye to brain and it converts impulses from brain to the retina .

iii. Oculomotor nerve : Third pair of cranial nerves named as CN3. This nerve is responsible for movement of the eyeball.

iv. Trochlear nerve : Fourth pair of cranial nerves named as CN4. This nerve responsibility for supplying of superior oblique muscles of eyeball

v. Trigeminal nerve : CN5 is the largest pair of cranial nerves. This nerve convey information to the skin, mucous membrane

vi. Abducens nerve : CN6 is six pair of cranial nerve and this nerve controls the movement of rectus muscles

Vii. Facial nerve : CN7 is seven pair of cranial nerve and the function of this nerve is to control facial muscles expressions and also gives taste sensation

Viii. Vestibulocochlear nerve : CN8 is responsible for hearing and balancing and it brings information from the inner ear.

ix. Glossopharyngeal nerve : CN9 nerve supplies the tongues and pharynx. And receive sensory fibers.

x. Vagus nerve : CN10 is basically mixed nerve which contains parasympathetic fibers and supply to lungs, heart and digestive tract.

xi. Spinal accessory: CN11 has two components, spinal part and cranial part and this nerve arises from medulla.

xii. Hypoglossal nerve : CN12 is the last twelve pairs of cranial nerves, the nerve supply muscles of the tongue .

Pluripotent Vs Totipotent:

The differences between pluripotent and Totipotent base on,


Pluripotent: pluripotent stem cells are those cells which have the ability to makes the various type of cells and it consists of three germs layers in embryo, these layers are

i. Endoderm

Endoderm is a germ layer which gives tissues or organs. This layer is responsible for formation of gut and endoderm cells present in diploblastic and triploblastic cells.

ii. Mesoderm

This layer is present in embryos and it may raise specialized tissue types. Endoderm is found in triploblastic organisms and it plays a vital role in animal development.

iii. Ectoderm

Ectoderm also forms in embryos during development. This layer covers the outside of embryo and it is found in diploblastic organisms in which endoderm and one of these three layers are found in triploblastic with both endoderm and mesoderm.

Totipotent: Totipotent stem cells having ability to differentiate into more 200 functionally distinct types of body cells in humans.

Pluripotent Vs Totipotent: Potential difference

Pluripotent: pluripotent seen cells having low potential.

Totipotent:  Totipotent stem cells having large or optimal number of potential.

Sequence of cells:

Pluripotent: for the development of totipotent stem cells that’s followed by development of pluripotent cells.

Totipotent: these cells are derived earlier.

Research use:

Pluripotent : these cells are used higher in number in research because they are easily obtainable.

Totipotent: these cells are useless in research because they are less achievable to embryonic cells.


Pluripotent: embryonic stem cells are examples of Pluripotent.

Totipotent: zygotes spores are examples of Totipotent.

  • Pluripotent and Totipotent cells are found in the beginning developmental stages of your body when fertilization is complete and the zygote is divided by the process of mitosis and produces a cell mass namely morula.
  • Morula is to be Totipotent and has the ability to differentiate the types of cells. It can be differentiated into embryo and thud embryonic cells have the ability to differentiate these three layers in humans known as pluripotent and these three layers are responsible for differentiating the tissues and also we as multipotent.