Title: Introduction to cell, tissues and organ Objectives: 1.
To study the different type, function, structure and histology of cell, tissue, and organs in human body. 2. To learn how to identify different cell and tissue based on their structure and shape. 3. To learn how to use the microscope properly to observe the slide of different cell and tissue. Introduction: Cell is the basic structural and functional units of an organism that are composed of chemicals.
Cell is the smallest living unit in the human body.Cell is divided into three main parts which are the plasma membrane, cytoplasm, and nucleus. The plasma membrane forms the cell flexible outer surface, separating the cell’s internal environment(everything inside the cell) from the external environment(everything outside the cell). The cytoplasm consists of all the cellular contents between the plasma membrane and the nucleus.
The nucleus is a large organelle that houses the most of a cell’s DNA (Tortora & Derrickson, 2011). Tissues are the group of cells and the materials surrounding them that work together to perform a particular function.There are four basic types of tissues in human body, which are the connective tissue, muscle tissue, epithelial tissue, and nervous tissue. Connective tissue connects, supports, and protects body organs while distributing blood vessels to other tissue. Muscular tissue contracts to make body parts move and generates heat. Epithelial tissue covers body surfaces, lines hollow organs and cavities, and forms glands.
Nervous tissues carry information from one part of the body to another through nerve impulses. Organs are structures that are composed of two or more different type of tissues.Each of them has specific function and usually has recognizable shape. Epithelial tissue consists of cell arranged in continuous sheets, in either single or multiple layers. Simple epithelium is a single layer of cells.
Pseudostratified epithelium appears to have multiple layers of cells because the cell nuclei lie at different levels and not all the cell reach the apical surface. Stratified epithelium consists of two or more layers of cells. Blood tissue consists of blood plasma and formed elements which are the red blood cells(erythrocytes), white blood cells(leukocytes), and platelets(thrombocytes).Integumentory system consists of superficial, thin epidermis and a deep, thicker dermis, deep to the is the subcutaneous layer which attaches the dermis to underlying fascia. Cartilage is a flexible connective tissue found in many areas of human body.
There are three types of cartilage which are hyaline cartilage, fibrocartilage, and elastic cartilage. Cartilage is a relatively inactive tissue that grows slowly and avascular. Bone tissue is classified as either compact or spongy, depending how its extracellular matrix and cells are organized. Compact bone is an osteon or haversian system.
Each osteon has four parts, the lamellae, lacunae, canaliculi, and the central canal. Spongy bone lacks osteon. Rather, it consists of columns of bone called trabeculae, which contain lamellae, osteocytes, lacunae and canaliculi. Discussion: 1. Simple epithelium is one cell thick, that is, every cell is in direct contact with the underlying basement membrane.
It is generally found where absorption and filtration occur. Squamous epithelia are found lining surfaces utilizing simple passive diffusion such as the alveolar epithelium in the lungs.Specialized squamous epithelia also form the lining of cavities such as the blood vessels (endothelium) and pericardium (mesothelium) and the major cavities found within the body. They fit closely together in tissues; providing a smooth, low-friction surface over which fluids can move easily. Cuboidal cells are roughly cuboidal in shape, appearing square in cross section cuboidal epithelium is commonly found in secretive or absorptive tissue: for example the (secretive) exocrine gland the pancreas and the (absorptive) lining of the kidney tubules as well as in the ducts of the glands.
Columnar epithelial cells are elongated and column-shaped. Columnar epithelium forms the lining of the stomach and intestines. Some columnar cells are specialized for sensory reception such as in the nose, ears and the taste buds of the tongue. Goblet cells are found between the columnar epithelial cells of the duodenum. They secrete mucus, which acts as a lubricant(Wikipedia, 2011). 2.
Stratified epithelium differs from simple epithelium in that it is multilayered. Stratified squamous epithelium cell consists of squamous epithelial cells arranged in layers upon a basement membrane.This type of epithelium is well suited to areas in the body subject to constant abrasion, as it is the thickest and layers can be sequentially sloughed off and replaced before the basement membrane is exposed. It forms the outermost layer of the skin and the inner lining of the mouth, esophagus and vagina.
Stratified keratinized surfaces are protected from abrasion by keratin and kept hydrated and protected from dehydration by glycolipids produced in the stratum granulosum. Stratified cuboidal epithelia is a type of epithelial tissue composed of cuboidally shaped cells arranged in multiple layers.They protect areas such as ducts of sweat glands, mammary glands, and salivary glands. Stratified columnar epithelia is a type of epithelial tissue composed of column shaped cells arranged in multiple layers. Stratified columnar epithelia are found in the ocular conjunctiva of the eye, in parts of the pharynx and anus, the female’s uterus, the male urethra and vas deferens.
The cells function in secretion and protection(Wikipedia, 2011) 3. Blood cell consists of three general categories, which are the erythrocytes, leucocytes and platelets.Erythrocytes are primarily for carrying oxygen and some carbon dioxide. The cells have the shape of biconcave lens, this increase the surface area of red blood cells, and provide a greater area for oxygen and carbon dioxide diffusion. Leukocyte are responsible for the defense of the organism.
Leukocytes divide into two categories, which are granulocytes and agranulocytes. The term granulocytes is due to the presence of granules in the cytoplasm of these cells. These granules have a different affinity towards neutral, acid or basic stains and give the cytoplasm different.Granulocytes distinguish themselves in neutrophil, eosinophil, and basophil. Neutrophil are active in phagocyting bacteria and are present in large amount in the pus of wounds. Eosinophil attack parasites and phagocyte antigen-antibody complexes.
Basophil secrete anti-coalagent and vasodilatory substances as histamines and serotonin. The agranulocytes distinguish into lymphocytes and monocytes. Lymphocytes are the main constituents of the immune system which is a defense against the attack of pathogenic microorganisms such as vurses, bacteria, fungi and protista.Monocytes are the precursors of macrophages(Tagliasacchi & Carboni, 1997).
Platelets are involved in blood coagulation and have a lifetime of about 9 days. 4. Integumentary system is the organ system that protects the body from damage, comprising the skin and its appendages. The integumentary system has a variety of function. It may serve to waterproof, cushion, and protect the deeper tissues excrete waste, and regulate temperature, and is the attachment site for sensory receptors to detect pain, sensation, pressure, temperature. The integumentary system also provides vitamin D synthesis.
The skin of human body divide into two major categories, the epidermis and dermis. Epidermis further divide into four layer which are stratum basale, stratum spinosum, stratum granulosum, and stratum corneum. Stratum basale is the deepest layer, it consists of stem cells that undergo cell division to produce new keratinocytes. Stratum spinosum consists mainly of numerous keratinocytes, some retain their ability to divide. The keratinocytes of this layer produce coarser bundles of keratin in intermediate filament than those of the basal layer.
Stratum granulosum consists of flattened keratinocytes that are undergoing apoptosis. The nuclei and other organelles of these cells begin to degenerate as they move farther from their source of nutrition. Stratum corneum consists of dead, flat keratinocytes that contain mostly keratin. In skin of fingertips, palms and soles, stratum lucidum are present. Stratum lucidum consists of flattened clear, dead keratinocytes that contain large amounts of keratin and thickened plasma membrances.
This provides an additional level of toughness in this region of thick skin(Wikipedia, 2011). . Hyaline cartilage found as supportive tissues in the nose, ears, trachea, larynx, and smaller respiratory tubes. Hyaline cartilage subsequently appears as a very uniform, glossy type tissue with evenly dispersed chondrocytes in lacunae.
As articular cartilage, hyaline is found covering the articular surfaces of bones in synovial joints. Hyaline cartilage reduces friction and acts as shock-absorbing tissue. Hyaline cartilage also forms the costal cartilages where ribs attach to the sternum and is the precursor to bone in most of the embryonic skeleton.Elastic cartilage is found in the pharyngotympanic(eusatachian) tubes, epiglottis, and ear lobes where needs dictate supportive tissues possess elasticity.
Elastic cartilage has a preponderance of dark-staining elastic fibers embedded in ground substance. The function of elastic cartilage is to maintain shape and flexibility of the organ, and provide strengthens and supports to our body. 6. Compact bone tissue consists of osteons, that contain lamellae, lacunae, osteocytes, canaliculi, and central canal.
The wall of the disphysis is composed of tightly packed tissue called compact bone.Bone provide support, protection, storage, houses blood-forming tissue and serves as levers that act with muscle tissue to enable movement. Spongy bone located in the interior of the bone, protected by a covering of compact bone. Spongy bone lacks osteon. Rather, it consists of columns of bone called trabeculae, which contain lamellae, osteocytes, lacunae and canaliculi.
Spongy bone is light, which reduces the overall weight of the bone. This reduction in weight allows the bone to move more readily when pulled by a skeletal muscle. The trabuculae of spongy bone support and protect the red bone marrow.Conclusion: Cell, tissue and organ has specific structure that help them to play a significant role in human body in order to maintain the internal and external environment. Connective tissue protect and support the body and its organs. Various types of connective tissues bind organs together, store energy reserve as fat, and help [rovide the body with immunity to disease-causing organisms.
Epithelial tissues cover body surfaces and line hollow organs, body cavities, and ducts, they also forms glands. This tissue allows the body to interact with both its internal and external environments.
