What is Epithelial Tissue?
Epithelial tissue is a kind of animal tissuethat is composed of polyhedral cells that are tightly aggregated joined tightly to each other as cellular layers that define the inside of hollow organs as well as protect the body’s the body’s surface.
Epithelial tissues or epithelium (epithelia plural) are laid out in continuous sheets in one or more layers. The sizes and shapes of epithelium tissue vary from tall columnar to low squamous. typically, the size of cells and shape are influenced by their role. The cells’ innermost layer in this tissues is attached by a basement membrane that is an layer of extracellular made up of collagen and laminin.
The epithelial tissue has avascularity, but without a blood supply. The intake of nutrients as well as the elimination of waste materials are accomplished through diffusion through the tissue beneath that epithelial layer. The cells do not have an electrical supply. Epithelial tissue can be capable of constant renewal and repair because they are able to sustain an extremely high rate of cell division. Dead or damaged cells are sloughed off and replaced by fresh cells.
Based on the location of their origin There are two major epithelial types: glandular epithelium and covering epithelium. The covering epithelium is the part that is the outer layer of the skin, as well as many internal organs such as the blood vessels as well as body cavity. It is further subdivided into stratified and simple epithelium based on their complexity and the amount of cell layers.
The glandular epithelium is a line that runs across different glands and their drains throughout the body, which , in turn, proliferate to make various hormones and enzymes. The glandular epithelium can be divided into endocrine and exocrine glands based on existence of the ducts. Epithelial tissue is the initial barrier against harmful microorganisms. It additionally protects the tissue from radiation, desiccation toxins as well as physical injury. In addition, glandular epithelial tissue plays a role in production of numerous important compounds. The epithelial tissues of the intestinal tract plays a role in absorption. It is also involved in the skin, it also serves the functions of sensation and reception.
Examples of epithelial tissue
Simple columnar epithelium
The columnar epithelium is the simplest, as with all epitheliums of a simple type is composed of only one layer of cells that have a column-like shape. They are tall and. The cells are linked with a basement membrane, which is composed of two layers: the basal layer, and the reticular layer. The simple columnar epithelium can be located in the lining epithelium within various organs, and it is frequently altered to make it better suitable for a particular function.
The stomach’s columnar epithelium does not have any structures on its surface. The free cell surface that line the small intestine are covered by microvilli, which enhances the surface area for absorption of nutrients through the small intestinal. The epithelium that lines the trachea is also ciliated , and also has goblet cells that produce mucus. In the uterine tube, the ova are pushed toward the uterus through the an action of ciliation in the columnar epithelium. The columnar epithelium of different organs of the body fulfills diverse functions that range from absorption to security.
Endocrine glands
The glands known as the endocrine glands are those without ducts which secrete hormones. They are lined with glandular epithelium. The epithelium contains various components of the glands. In certain glands, it forms the parenchyma whereas in others it forms the ducts as well as the surfaces inside the gland. The endocrine glands’ secretions known as hormones, are released into the bloodstream and do not flow through the conduit.
These effects are far-reaching as they circulate throughout the body through the bloodstream. Endocrine glands can be found in the pituitary glands at the brain’s base the pineal gland located in the brain the thyroid gland and parathyroid glands located near the in the larynx (voice box) the adrenal glands next to kidneys, pancreas close to the stomach, ovaries within the pelvic cavity the testes in the scrotum and the thymus in the thoracic cavity.
Connective Tissue Definition
Connective tissue is a kind of animal tissue comprised of fibers, cells, and gel-like substances which support and provides shape to the body.
Connective tissue is the largest and most prolific tissue in the human body. It is composed from cells as well as extracellular matrix. The cells that make up connective tissue originate from embryonic mesenchymal cells. The connective tissues of every kind are composed of mature cells, also known as blast cells which maintain the capacity to divide and the secretion of extracellular matrix.
The cells in the various tissues are macrophages, fibroblasts mast cells, plasma cells, adipose and mast cells as well as chondrocytes, leukocytes etc. The matrix or the ground substance within connective tissue could be semifluid or fluid or gelatinous that holds cells, binds them together, holds water, and acts as a conduit for exchange of chemicals between blood cells and the cells. The shape of extracellular matrix is a determinant for many of the characteristics of the tissue. For instance cartilage’s extracellular matrix is firm , but flexible. The extracellular matrix of bone however, is hard and rigid.
Connective tissue is typically very vascularized and well-involved; it is awash in supply of nerves and blood with the exception of the cartilage and tendons which is not vascular and does not have nerves. Due to the variety of extracellular matrix and cells and the different proportions, connective tissue are classified into different groups. There are connective tissues that are liquid cartilages, bones and the adipose tissue. Connective tissue’s functions are also different depending on the form and the where it is located.
Connective tissues, like bones, provide support and structures to the body. cartilage aids in movement. Adipose tissue beneath the skin, functions as a heat insulation and assists in connecting the skin to the tissues beneath. The ligaments and tendons that are located throughout the body function as a connector for muscles, bones, and cartilages. Connective tissue with liquids such as lymph and blood aids in the transportation of waste materials and nutrients and also contains immune cells that defend against invaders from outside.
Examples of connective tissue
Bones
Bones are connective tissue in which alive cells, tissues and other elements are contained within non-living matter. Bone tissues are part of the skeleton structure in vertebrates and humans. Bone tissues within the structure of hard tissue make up a honey-comb structure internally made of two cells, osteoblasts as well as osteoclasts. Bones are mineralized tissues made up of different types of tissues inside them, such as bone marrow, the periosteum, endosteum, as well as blood vessels. They are found in various dimensions and shapes with various types of complexity that serve various functions. Since bone tissue is a connective tissues, they are extremely vascularized and is enclosed by other connective tissues. It is also vascularized by multiple nerve supply.
Blood
The blood is a connective tissue which circulates continuously throughout the body, providing constant connection between tissues that are far from one another. Blood is made up of a transparent straw-colored, watery substance known as plasma, along with a variety of kinds of blood cells which are suspended. Plasma’s constituents are mainly water and suspended and dissolved substances like plasma proteins inorganic salts, nutrients substances that are waste, hormones and gases.
The blood cells are leukocytes, erythrocytes and platelets, all of which are created in the bone marrow red. However, some lymphocytes are made within lymphoid tissue. The connective tissue of blood which is essential for the transportation of different substances like nutrients and gases. Additionally, it is also a conduit for substances that are harmful to organs such as kidneys and liver. The blood platelets are a source of certain cells known as thrombocytes which play a role in formation of clots in blood.
Difference between Epithelial tissue and Connective tissue – Epithelial tissue vs Connective tissue
| Basis for Comparison | Tissue epithelial | Connective tissue |
| Definition | Epithelial tissue is a kind of tissue found in animals, made up of tightly aggregated polyhedral cells joined tightly to each other by cellular sheets that define the inside of hollow organs and are covered by the body’s the body’s surface. | Connective tissue is a kind of tissue in animals made of fibers, cells and gel-like substances which support and provides the body structure. |
| Emeryonic development | The epithelial cells originate from all three germ layers of the embryonic germ (ectoderm mesoderm endoderm). | Connective tissue cells are formed from mysodermal embryonic germ layers. |
| Components | The epithelial tissue is comprised of epithelial cells, as well as an insignificant amount of extracellular matrix. | The connective tissue is made up of a variety of cells as well as an additional amount of extracellular matrix. |
| The arrangement of cells | The epithelial cells tissue are organized as cell sheets in one or more layers. | The connective tissue are dispersed across the matrix, but in no specific arrangement. |
| Basement Membrane | The cells of the outermost epithelial tissue layer are linked to the basement membrane. | The basement membrane is not present inside connective tissue. |
| Location | Epithelial tissue is the cover of organs and is the tissue that covers the majority of organs. | Connective tissue usually lies beneath epithelial tissue. |
| Vascularity | Epithelial tissue has a vascular structure but none of the blood vessels. | Connective tissue can be vascular, and consequently, are abundant in blood vessels, apart from cartilages and tendons. |
| Innervation | The epithelial tissue doesn’t also have nerve supply. | Connective tissue is surrounded except for cartilage. |
| Nutrition | The epithelial cells of the tissue receive their nutrition from the cells beneath through diffusion. | The cells’ nutrition and connective tissue is acquired through blood vessels that supply blood to the cells. |
| Bound by | The cells are linked to one another by a variety of cell junctions such as desmosomes or the hemidesmosomes. | The cells are linked via collagen and elastin together with blood vessels. |
| Types | The epithelial tissues are divided into two main types , and further subdivided into different types;1. Epithelium covered by a coveringa. Simple epitheliumb. Epithelium Stratifiedc. Pseudostratified epitheliumD. Epithelium transitional2. Epithelium with a Glandular appearance | Connective tissues can also be classified into different types according to the type of cells and the elements that make up the extracellular matrix.1. Connective tissue loose and loose2. Dense connective tissue3. Cartilage4. Bones5. Liquid connective tissuea. Bloodb. Lymph |
| Abundant | Epithelial tissue is more scarce in connective tissues. | Connective tissue is the largest and most of the animal tissues that are abundant. |
| Immune function | Epithelial tissue serves as a barrier to protect against invaders from outside. | Connective tissue comprises cells that resemble mast cells as well as macrophages, which kill pathogenic organisms through the process of phagocytosis. |
| Secretion | Glandular epithelium releases hormones and enzymes that are necessary for different metabolic processes. | Connective tissue doesn’t release these chemicals that are metabolically active. |
| Found in | Epithelial tissue is present in different organs such as the buccal cavity, the skin and the blood vessel lining and glands, body cavities along with their drainage ducts. | The connective part of the body which forms bones cartilages, cartilages, adipose tissue as well as reticular tissue. blood. |
