The cell is the basic structural and functional unit of all known living organism. It is the smallest unit of life that is classified as a living thing and is often called the building block of life. Some organism such as most bacteria, are unicellular (consist of a single cell) and other organism such as human, are multicellular. Each cell can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary. It also stores its own set of instructions for carrying out each of these activities.
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All cells have a ‘skin’ called the plasma membrane, protecting it from the outside environment. The cell membrane regulates the movement of water, nutrients and wastes into and out of the cell. Inside of the cell membrane are the working parts of the cell. At the center of the cell is the cell nucleus. The cell nucleus contains the cell’s DNA, the genetic code that coordinates protein synthesis. In addition to the nucleus, there are many organelles inside the cell – small structures that help carry out the day-to-day operations of the cell. One important cellular organelle is the ribosome. Ribosomes participate in protein synthesis. The transcription phase of protein synthesis takes places in the cell nucleus. After this step is complete, the mRNA leaves the nucleus and travels to the cell’s ribosomes, where translation occurs. Another important cellular organelle is the mitochondrion. Mitochondria are often referred to as power plants of the cell because may of the reactions that produce energy take place in materials. Outside the cell wall is a gelatinous capsule which has antiphagocytic function so it determines the virulence of many bacteria. It also plays a role in attachment of the organism to mucous membranes. Most cells’ organelles fo cellular mobility are flagella. Flagella arise from cytoplasm and extrude through the cell wall, they are long and thick thread-like appendages, protein in nature. Another outer structure of the cell are Fimbriae (pili). Fimbriae are short and thin hair like filaments and are responsible for attachment of bacteria to specific receptors oh human cell.
II. DESCRIBE AND DISTINGUISH BETWEEN THE CELL AND TISSUE ORGANIZATION AND SYSTEM.
As the diagram shows
CELL TISSUE ORGAN SYSTEM HUMAN BODY
A group of cells with same structure and functions will become tissue and one to several dozen processes will be called organ and group of organ will function as a system until it join with other functional and anatomical unit of the human body or organism.
There are many different types of cells in the human body. None of these cells function well on their own, they are part of the larger organism that is called human.
TISSUES
Cells group together in the body to form tissues – a collection of similar cells that group together to perform a specialized function. There are 4 primary types in the human body: epithelial tissue, connective tissue, muscle tissue and nerve tissue.
1) Epithelial TIssue – The cells of epithelial tissue pack tightly together and form continuous sheets that serve as liningd in different parts of the body. Epithelial tissue serves as membranes lining organs and helping to keep the body’s organs separate, in palce and protected. Some examples of epithelial tissue are the outer layer of the skin, the inside of the mouth and stomach, and the tissue surrounding the body’s organ.
2) Connective Tissue – Connective tissue adds support and structure to the body. Most types of connective tissue contain fibrous strands of the protein collagen that add strength to connective tissue. Some examples of connective tissue include the inner layers of skin, tendons, ligamnets, cartilage, bone, fat tissue and blood.
3) Muscle Tissue – This type of tissue is a specialized tissue taht can contract. Muscle tissue contains the specialized proteins actin and myosin that slide past one another and allow movement. Examples of muscle tissue are contained in the muscle throughout your body.
4) Nerve Tissue – Nerve tissue contains two types of cells: neurons and glial cells. Nerve tissue has the ability to generate and conduct electrical signals in the body. These electrical messages are manage by nerve tisse in the brain and transmitted down the spinal cord to the body.
ORGANS
An organ is a structure that contains at least two different types of tissue functioning together for a common purpose. The skin is the largest organ in the human body and is composed of three layers: the epidermis, dermis and subcutaneous layer. The epidermis is the outer lsyer of skin. It consists of epithelial tissue in which the cells are tightly packed together providing a barrier between the inside of the body and the outside world. Below the epidermis lies a layer of connective tissue called the dermis. Dermis contains blood vessels that nourish skin cells. It contains nerve tissue that provides feeling in the skin. The subcutaneous layer is beneath the dermis and consists mainly of a type of connective tissue called adipose tissue. Adipose tissue is also known as fat and helps cushion th eskin and provide protection from cold temperature.
ORGAN SYSTEMS
Organ systems are composed of two or more different organs that work together to provide a common function. There are 10 major organ systems in the human body.
1) Skeletal System: The main role of the skeletal system is to provide support for the body, to protect delicate internal organs and to provide attachment sites for the organs. Major organs are bones, cartilages, tendons and ligaments.
2) Muscular System: The main role of the muscular sysem is to provide movemet. Muscles work in pairs to move limbs and provide the organism with mobility. Muscles also control the movement of material through some organs, such as the stomach and intestines, and the heart and circulatory system. Major organs are skeletal muscles and smooth moscles throughout the body.
3) Circulatory System: The main role of this system is to transport nutrients, gases, hormones and wastes through the body.
Major organs are heart, blood vessels and blood.
4) Nervous System: The main role of the system is to relay electrical signals through the body. The nervous system directs behaviour and movement and, along with the endocrine system, controls physiological processes such as digestion, circulation, etc.
Major organs include brain, spinal cord and peripheral nerves.
5) Respiratory System: The main role of the respiratory system is to provide gas exchange between the blood and the environment. Primarily, Oxygen is absorbed from the atmosphere into the body and carbon dioxide is expelled form the body. Major organs are nose, trachea and lungs.
6) Digestive System: The main role of th esystem is to breakdown and absorb nutrients that are necessary for growth and maintenance. Major organs are mouth, esophagus, stomach and large intestines.
7) Excretory System: The main role os this system is to filter out cellular wastes, toxins and excess water or nutrients from the circulatory system. Major organs are kidneys, ureters, bladder and urethra.
8) Endocrine System: The main role of the endocrine system is to relay chemical messgaes through the body. In conjunction with the nervous system, these chemical messages help control physiological processes such as nutrient absorption, growth, etc.
Many organs exist in the body taht secrete endocrine hormones. Among these are hypothalamus, pituitary, thyroid, pancreas and adrenal glands.
9) Reproductive System: The mai role of this system is to manufacture cells that allow reproduction. In the male, sperm are created to inseminate egg cells produced in the female. Major organs for female are ovaries, uterus, vagina and mammary glands; for male testes, seminal vesicles and penis.
10) Lymphatic/Immune System: The main role is to destroy and remove invading microbes and viruses from the body. The lymphatic system also removes fat and excess fluids from the blood.
Major organs are lymph, lymph nodes and vessels, white blood cells, T- and B- cells.
III. EXPLAIN TISSUE STIMULUS, ELECTRICAL FUNCTION AND BALANCE AND IT’S IMPLICATIONS FOR INTERACTION BETWEEN CELLS AND SYSTEM.
Neurons are the structural units of the nervous system that carry out the functions of the systems by conducting impulses. They are highly specialized and amitotic, which means that if a neuron is destroyed it cannot be replaced. Functionally, neurons are classified as afferent, efferent, or association neurons, according to the direction in which they transmit impulses relative to the central nervous system. Each neuron has three basic parts:
Cell body, which is similar to other type of cells
One or more dendrite, which transit impulses to the cell body
A single axon, which transmits impulses away from the cell body
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