Each tissue of the body consists of millions of cells, with different sizes, shapes, and functions. Subdivisions of each tissue type are found within the four main types. They are – epithelial tissues, connective tissues, muscular tissues, and nervous tissues.
A. Epithelial tissue
There are tissues in this group that cover the body, line hollow organs, and line tubes. Epithelium function is closely correlated with its structure, including a variety of features such as dehydration protection, chemical absorption, and mechanical damage absorption. The epithelia may be either simple: a single layer of cells or stratified: a layer of cells on top of another.
There are 6 types of epithelial tissues:
Structure - One layer of flat cells makes up the simple squamous epithelium. The cells form an extremely thin and smooth membrane, allowing diffusion between them with ease.
Location and Functions - Lung alveoli - thin enough for gases to diffuse, To prevent abnormal blood clotting, capillaries shouldn't be thick-they should be thin to permit exchanges of materials.
2. Stratified squamous
Structure - In stratified squamous epithelium, cells are mainly flat, except for lower-layer cells that are rounded. Cells are continually renewed in the lowest layers by mitosis to replenish those worn off. It produces keratin in this epithelium, which makes up the epidermis of the skin, and dead skin cells are found there. In the oral cavity, esophagus, and vagina, stratified epithelium of the non-keratinizing type is present. Surface cells live in these areas and are responsible for forming the mucous membranes in these organs. Since the cells of which it is made are so close together, it acts as a barrier to microbes in all its locations on the body
Location and Functions - the epidermis - Pathogens are unable to penetrate the dead epidermis cells, living cells line the inside of the esophagus, and the vagina, forming a barrier to pathogens.
3. Cuboidal
Structure - A layer made up of cube-shaped cells that fit closely together lies on top of the basement membrane. This type of tissue is found in the thyroid gland and the salivary glands as well. In addition to forming the kidney tubules, it is found in many glands in the body. Secretions, adsorptions, and excretions are all actively controlled by the cuboidal epithelium.
Location and Functions – thyroid gland - Synthesizes thyroid hormone thyroxine, salivary gland - It is a gland that secretes saliva, kidney tubules - Tubules in the kidneys reabsorb useful components back into the blood.
4. Columnar
Structure - An arrangement of rectangular cells within a basement membrane makes up this layer. There are taller and narrower cells in the columnar region, which are specialized for secretion and absorption. As a result of the large surface area of microvilli in the small intestine, nutrients are more easily absorbed. There are ciliated cells and goblet cells in the columnar epithelium of the trachea which secrete mucus. Inhaled particles that stick to mucus are carried by the respiratory tract's cilia towards the throat. Ciliary action propels ova through uterine tubes and into the uterus.
Location and Functions – The lining of the stomach secretes gastrin-the gastric juice, and the lining of the small intestine (which is lined with microvilli) secretes enzymes and absorbs digestive products.
5. Transitional
Structure - Pear-shaped cells are layered on top of one another. An epithelium that undergoes the transition from round to squamous appearance is called the transitional epithelium. As urine fills the bladder, the bladder's lining stretches. Cells on the bladder surface are rounded when the bladder is empty. The cells in the bladder flatten as they fill up. Throughout the bladder's transitional epithelium, the bladder can stretch without tearing its lining.
Location and Functions - lining in the urinary bladder - A bladder lining that allows expansion without rupturing it.
6. Ciliated
Structure - In columnar epithelium, cilia are located on the free surfaces of cells. Nasal cavities, larynxes, tracheas, and large bronchial tubes are lined with ciliated epithelia. By sweeping up mucus and dust from the lungs, as well as dust and bacteria surrounding them, the cilia allow them to enter the pharynx where they are swallowed. After the bacteria reach the stomach, hydrochloric acid destroys them. Particulate pollution and pathogens are almost nonexistent in the air reaching the lungs.
Location and Functions - the lining of trachea - Mucus, and dust are swept from the trachea to the pharynx by the trachea's lining, lining of fallopian tube - It sweeps the ovum toward the uterus as it passes through the fallopian tubes.
B. Connective tissue
There are 7 types of connective tissues that include :
1. Blood
Structure - Furthermore, blood is a connective tissue as well as a liquid. Constant communication occurs among tissue distant from each other due to its continuous circulation around the body. Besides oxygen entering the tissues from the lungs, carbon dioxide also makes its way into the lungs from the tissues. The lungs emit nutrients from the alimentary canal to the tissues, and it excretes cell waste to the excretory organs, in particular, the kidneys Among blood's components are cells, which are the living cells. The plasma that makes up the matrix of blood accounts for approximately 52% to 62% of the body's total blood volume. Among the dissolved substances in plasma are salts, nutrients, gases, and waste products.
Redbone marrow, such as hip bones and vertebrae, has both flat and irregular cells that make up the primary hemopoietic tissue (which produces blood cells). Red blood cells, platelets, and five types of white blood cells qualify as different categories of blood cells. A white blood cell is either neutrophil, eosinophil, basophil, monocyte, or lymphocyte.
Location and functions - they are circulating within blood vessels. Materials are transported by plasma, Oxygen is carried by RBCs, Pathogens are destroyed by WBCs, Prevents bleeding with the help of platelets.
2. Areolar (loose) tissue
Structure - Fibroblasts are the cells that constitute areolar connective tissue (the loose kind). Fibroblasts produce protein fibers, and blast cells are "producing" cells. Collagen fiber is very strong. An elastic fiber, however, can recoil after being stretched back to its original length. There are protein fibers in the matrix and different types of tissue fluids that make up areolar connective tissue.
Location and functions - subcutaneous, Mucous membrane (digestive, respiratory, urinary, reproductive tracts) is connected to the skin; WBCs destroy disease-causing pathogens, Pathogens are destroyed by WBCs.
3. Adipose tissue
Structure - As the name implies, adipocytes are specific cells that store fat in minute droplets within adipose tissue.
Location and functions - subcutaneous, Excess energy is stored, Induces inflammation around the eyes and kidneys, and alters nutrition consumption, appetite, and nutrient use, cushions.
4. Fibrous tissue
Structure - Collagen fibers, a few fibroblasts, and parallel (regular) collagen fibers define this structure
Location and functions - tendons and ligaments (regular) - Ability to handle forces of joint movement Dermis (irregular), A layer of strong tissue that lines the inside of the skin.
5. Elastic
Structure - A majority of elastin fibers (matrix) with a few fibroblasts.
Location and functions - the wall of large arteries - Ensures blood pressure is maintained around lung alveoli, Maintains a normal exhalation rate.
6. Bone
Structure - "Osteo" is the prefix used to designate bone so that cell types in bones are called osteocytes. Besides being strong, hard, and not flexible, bone's matrix is composed of calcium salts and collagen. On long bones, such as the femur, the osteocytes, blood vessels, and matrix are arranged in very precise patterns called Haversian systems or osteons.
Location and functions - bones - Provide support to the body, Ensure that internal organs are protected from mechanical damage, Keep excess calcium, Protect and contain the red blood cells.
7. Cartilage
Structure - It is made up of a protein-carbohydrate matrix rather than calcium salts, and it is also more water-based than that bone, which is why it is so resilient. Despite being firm, it is also flexible and smooth. It's a smooth surface that prevents friction on the surfaces of joints and bones.
The cartilage matrix is made up of cartilage cells called chondrocytes. This matrix does not contain capillaries, so cartilage cells are nourished through diffusion according to their needs.
Location and functions - the wall of the trachea - Keeps airways open at joint surfaces, Smooth nose tip, and outer ear to prevent friction, The vertebrae support each other, Provide shock absorption.
There are 3 types of muscular tissues that include -
1. Skeletal muscle
Structure - The muscle is described as skeletal because it moves bones [of the skeleton], striated because it exhibits marked striations (stripes) upon microscopic examination, and voluntary because it is under conscious control. The skeletal muscle may also be referred to as voluntary muscle or striated muscle. The skeletal muscle cells have many nuclei, are cylindrical, and striped.
Location and functions - attached to bones - The skeleton is moved and heat is produced.
2. Smooth muscle
Structure - A smooth muscle is also known as an involuntary muscle or a visceral muscle. It has one nucleus and smooth ends and does not have striations.
Location and functions - the wall of arteries - Keeps blood pressure in check Stomach and intestinal walls, Intact Iris of an eye during peristalsis, Pupil size is regulated.
3. Cardiac muscle
Structure - The heart is composed of cardiac muscle cells. There are a few striations, one nucleus per cell, and branches between each one.
Location and functions - The walls of the heart chambers – pump blood.
D. Nervous tissue
1. Neuron (nerve cell)
Structure – it contains the nucleus
Functions – help in regulating the functioning of the neuron.
2. Axon
Structure – a cellular process
Functions – it helps in carrying impulses away from the cell body.
3. Dendrites
Structure – a cellular process
Functions – it helps in carrying impulses towards the cell body.
4. Synapse
Structure - An axonal gap between two neurons is the difference between their dendrites.
Functions - The transmission of impulses from neuron to neuron.
5. Neurotransmitters
Structure – they are the chemicals released by the axons.
Functions – it helps in the transmission of impulses across a synapse.
6. Neuroglia
Structure – these are the specialized cells in CNS
Functions – it forms myelin sheaths and has other functions as well.
7. Schwann cells
Structure – these are the specialized cells in PNS.
Functions – it helps to form myelin sheaths around neurons.
A. Epithelial tissue
There are tissues in this group that cover the body, line hollow organs, and line tubes. Epithelium function is closely correlated with its structure, including a variety of features such as dehydration protection, chemical absorption, and mechanical damage absorption. The epithelia may be either simple: a single layer of cells or stratified: a layer of cells on top of another.
There are 6 types of epithelial tissues:
Structure - One layer of flat cells makes up the simple squamous epithelium. The cells form an extremely thin and smooth membrane, allowing diffusion between them with ease.
Location and Functions - Lung alveoli - thin enough for gases to diffuse, To prevent abnormal blood clotting, capillaries shouldn't be thick-they should be thin to permit exchanges of materials.
2. Stratified squamous
Structure - In stratified squamous epithelium, cells are mainly flat, except for lower-layer cells that are rounded. Cells are continually renewed in the lowest layers by mitosis to replenish those worn off. It produces keratin in this epithelium, which makes up the epidermis of the skin, and dead skin cells are found there. In the oral cavity, esophagus, and vagina, stratified epithelium of the non-keratinizing type is present. Surface cells live in these areas and are responsible for forming the mucous membranes in these organs. Since the cells of which it is made are so close together, it acts as a barrier to microbes in all its locations on the body
Location and Functions - the epidermis - Pathogens are unable to penetrate the dead epidermis cells, living cells line the inside of the esophagus, and the vagina, forming a barrier to pathogens.
3. Cuboidal
Structure - A layer made up of cube-shaped cells that fit closely together lies on top of the basement membrane. This type of tissue is found in the thyroid gland and the salivary glands as well. In addition to forming the kidney tubules, it is found in many glands in the body. Secretions, adsorptions, and excretions are all actively controlled by the cuboidal epithelium.
Location and Functions – thyroid gland - Synthesizes thyroid hormone thyroxine, salivary gland - It is a gland that secretes saliva, kidney tubules - Tubules in the kidneys reabsorb useful components back into the blood.
4. Columnar
Structure - An arrangement of rectangular cells within a basement membrane makes up this layer. There are taller and narrower cells in the columnar region, which are specialized for secretion and absorption. As a result of the large surface area of microvilli in the small intestine, nutrients are more easily absorbed. There are ciliated cells and goblet cells in the columnar epithelium of the trachea which secrete mucus. Inhaled particles that stick to mucus are carried by the respiratory tract's cilia towards the throat. Ciliary action propels ova through uterine tubes and into the uterus.
Location and Functions – The lining of the stomach secretes gastrin-the gastric juice, and the lining of the small intestine (which is lined with microvilli) secretes enzymes and absorbs digestive products.
5. Transitional
Structure - Pear-shaped cells are layered on top of one another. An epithelium that undergoes the transition from round to squamous appearance is called the transitional epithelium. As urine fills the bladder, the bladder's lining stretches. Cells on the bladder surface are rounded when the bladder is empty. The cells in the bladder flatten as they fill up. Throughout the bladder's transitional epithelium, the bladder can stretch without tearing its lining.
Location and Functions - lining in the urinary bladder - A bladder lining that allows expansion without rupturing it.
6. Ciliated
Structure - In columnar epithelium, cilia are located on the free surfaces of cells. Nasal cavities, larynxes, tracheas, and large bronchial tubes are lined with ciliated epithelia. By sweeping up mucus and dust from the lungs, as well as dust and bacteria surrounding them, the cilia allow them to enter the pharynx where they are swallowed. After the bacteria reach the stomach, hydrochloric acid destroys them. Particulate pollution and pathogens are almost nonexistent in the air reaching the lungs.
Location and Functions - the lining of trachea - Mucus, and dust are swept from the trachea to the pharynx by the trachea's lining, lining of fallopian tube - It sweeps the ovum toward the uterus as it passes through the fallopian tubes.
B. Connective tissue
There are 7 types of connective tissues that include :
1. Blood
Structure - Furthermore, blood is a connective tissue as well as a liquid. Constant communication occurs among tissue distant from each other due to its continuous circulation around the body. Besides oxygen entering the tissues from the lungs, carbon dioxide also makes its way into the lungs from the tissues. The lungs emit nutrients from the alimentary canal to the tissues, and it excretes cell waste to the excretory organs, in particular, the kidneys Among blood's components are cells, which are the living cells. The plasma that makes up the matrix of blood accounts for approximately 52% to 62% of the body's total blood volume. Among the dissolved substances in plasma are salts, nutrients, gases, and waste products.
Redbone marrow, such as hip bones and vertebrae, has both flat and irregular cells that make up the primary hemopoietic tissue (which produces blood cells). Red blood cells, platelets, and five types of white blood cells qualify as different categories of blood cells. A white blood cell is either neutrophil, eosinophil, basophil, monocyte, or lymphocyte.
Location and functions - they are circulating within blood vessels. Materials are transported by plasma, Oxygen is carried by RBCs, Pathogens are destroyed by WBCs, Prevents bleeding with the help of platelets.
2. Areolar (loose) tissue
Structure - Fibroblasts are the cells that constitute areolar connective tissue (the loose kind). Fibroblasts produce protein fibers, and blast cells are "producing" cells. Collagen fiber is very strong. An elastic fiber, however, can recoil after being stretched back to its original length. There are protein fibers in the matrix and different types of tissue fluids that make up areolar connective tissue.
Location and functions - subcutaneous, Mucous membrane (digestive, respiratory, urinary, reproductive tracts) is connected to the skin; WBCs destroy disease-causing pathogens, Pathogens are destroyed by WBCs.
3. Adipose tissue
Structure - As the name implies, adipocytes are specific cells that store fat in minute droplets within adipose tissue.
Location and functions - subcutaneous, Excess energy is stored, Induces inflammation around the eyes and kidneys, and alters nutrition consumption, appetite, and nutrient use, cushions.
4. Fibrous tissue
Structure - Collagen fibers, a few fibroblasts, and parallel (regular) collagen fibers define this structure
Location and functions - tendons and ligaments (regular) - Ability to handle forces of joint movement Dermis (irregular), A layer of strong tissue that lines the inside of the skin.
5. Elastic
Structure - A majority of elastin fibers (matrix) with a few fibroblasts.
Location and functions - the wall of large arteries - Ensures blood pressure is maintained around lung alveoli, Maintains a normal exhalation rate.
6. Bone
Structure - "Osteo" is the prefix used to designate bone so that cell types in bones are called osteocytes. Besides being strong, hard, and not flexible, bone's matrix is composed of calcium salts and collagen. On long bones, such as the femur, the osteocytes, blood vessels, and matrix are arranged in very precise patterns called Haversian systems or osteons.
Location and functions - bones - Provide support to the body, Ensure that internal organs are protected from mechanical damage, Keep excess calcium, Protect and contain the red blood cells.
7. Cartilage
Structure - It is made up of a protein-carbohydrate matrix rather than calcium salts, and it is also more water-based than that bone, which is why it is so resilient. Despite being firm, it is also flexible and smooth. It's a smooth surface that prevents friction on the surfaces of joints and bones.
The cartilage matrix is made up of cartilage cells called chondrocytes. This matrix does not contain capillaries, so cartilage cells are nourished through diffusion according to their needs.
Location and functions - the wall of the trachea - Keeps airways open at joint surfaces, Smooth nose tip, and outer ear to prevent friction, The vertebrae support each other, Provide shock absorption.
There are 3 types of muscular tissues that include -
1. Skeletal muscle
Structure - The muscle is described as skeletal because it moves bones [of the skeleton], striated because it exhibits marked striations (stripes) upon microscopic examination, and voluntary because it is under conscious control. The skeletal muscle may also be referred to as voluntary muscle or striated muscle. The skeletal muscle cells have many nuclei, are cylindrical, and striped.
Location and functions - attached to bones - The skeleton is moved and heat is produced.
2. Smooth muscle
Structure - A smooth muscle is also known as an involuntary muscle or a visceral muscle. It has one nucleus and smooth ends and does not have striations.
Location and functions - the wall of arteries - Keeps blood pressure in check Stomach and intestinal walls, Intact Iris of an eye during peristalsis, Pupil size is regulated.
3. Cardiac muscle
Structure - The heart is composed of cardiac muscle cells. There are a few striations, one nucleus per cell, and branches between each one.
Location and functions - The walls of the heart chambers – pump blood.
D. Nervous tissue
1. Neuron (nerve cell)
Structure – it contains the nucleus
Functions – help in regulating the functioning of the neuron.
2. Axon
Structure – a cellular process
Functions – it helps in carrying impulses away from the cell body.
3. Dendrites
Structure – a cellular process
Functions – it helps in carrying impulses towards the cell body.
4. Synapse
Structure - An axonal gap between two neurons is the difference between their dendrites.
Functions - The transmission of impulses from neuron to neuron.
5. Neurotransmitters
Structure – they are the chemicals released by the axons.
Functions – it helps in the transmission of impulses across a synapse.
6. Neuroglia
Structure – these are the specialized cells in CNS
Functions – it forms myelin sheaths and has other functions as well.
7. Schwann cells
Structure – these are the specialized cells in PNS.
Functions – it helps to form myelin sheaths around neurons.
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