Specialization is a fundamental characteristic of multicellular organisms like human beings.
The most important benefit of specialization is that it trades off complexities. Individual elements become simpler and the organisation of these simpler elements becomes more complex. A typical example lies in the fact that single-cell organisms have a wide range of behavorial complexities,majority of which is less used, in order to respond to the range of possible environmental conditions they may encounter. That complexity will no longer be necessary if cells can rely on the specialised cells to adapt to varying conditions.
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Cell specialization ensures that there is no conflict in functioning of cells to perform a specific task. The specialisation process ensures an effective use of energy by the cells. A nerve cell could not function as a reliable communication channel between point A and point B if it also builds bone around itself, fills itself with haemoglobin to carry oxygen, accumulates fat, secrete stomach acid or feritilize an egg cell.
Cell specialisation ensures that specialised cells are ‘well equiped’ with mechanisms and structures to carry out a specific role. For examples, at the base of a sperm cell lies a power house of ATP called the mitochondria, unleashed prior to fertilisation to enable the sperm cell swim.
Perhaps the most important reason for specialization is that it reduces the number and type of messages to which the cell can respond. There are different types of molecular messages present in multicellular organism. Each cell responds to just a small part of these messages. It will be chaotic for a cell to retain the ability to respond to all these messages. Worse, a general-purpose cell would be susceptible to all viruses. Viruses infect a cell by binding to particular surface proteins. Since different surface proteins characterize different specialized cells, each kind of virus can infect only certain types of cells -those that have the right binding sites. For example the cold virus infects cells in the nasal passages, the hepatitis virus infects certain liver cells, the HIV virus infects certain cells in the immune system, and so forth. If every cell expressed all cell markers, any virus could bind to and infect all cells.
4.2 DESCRIBE MAJOR TISSUE TYPES AND THEIR FUNCTIONS.
A Tissue is a group of associated, similarly structured cells that perform specialized functions for the survival of the organism. There are four basic types of tissue: epithelial tissue, connective tissue (blood, bone, cartilage), muscle tissue, and nerve tissue.
Epithelial tissue covers or lines all body surfaces inside and outside the body. Epithelial tissue may be a single layer thick or several
cell layers thick. The cell layers are arranged in thin sheets, called
membranes, that are firmly attached to the underlying connective tissue by a permeable basement membrane.
Epithelial tissue is concerned with protection, secretion, absorption, and filtration.For example, the surface layer of the skin, the epidermis, has tightly packed epithelial cells and
protects the body from the elements; epithelial cells in glands secrete various liquids; epithelial cells in the small intestine absorb nutrients into the bloodstream.
Connective tissue, the most abundant and most widely distributed of all tissues, is found throughout the body. It consists of three elements: cells, ground substances (also called matrix or intercellular material) and fibres. Cells of these tissues are widely separated from one another, with a large amount of intercellular substance between them. There are five subtypes of connective tissue.
Embryonal connective tissue is found in the embryo and fetus. Vascular tissue, blood and lymph, is connectivetissue in which the intercellular material is plasma for blood and an ultrafiltrate of plasma for lymph. The lining of the blood and lymph vessels is called endothelium, and the lining of body cavities is called mesothelium. Connective tissue proper consists of several types, ranging from tough fibers to soft, gelatinous material. Cartilage is characterized by intercellular material that has a rubbery substance. Bone is a hard matrix due to the presence of lime salts. Connective tissue performs several different functions, ranging from connecting, supporting, and protecting other tissue to helping protect the body against disease. For example, bone serves as the main support system of the body, while tendons, ligaments, and fascia connect other tissues of the body. Blood transports oxygen, nutrients, and waste products, and helps to fight bacterial infection.
Muscle tissue accounts for nearly one-half of the total body weight and consists of three distinct subtypes: striated (skeletal) muscle, smooth (visceral) muscle and cardiac muscle.
Each type of muscle cell is designed to perform one basic function. Striated muscle is attached to bones that move the skeleton. Smooth muscle is located in the walls of hollow internal structures, such as the intestines and blood vessels, allowing such organs to expand and contract. Cardiac muscle occurs only in the heart, where it forms the walls and enables the heart to pump blood. Cardiac muscle cells, each of which has a nucleus, are slightly striated. Each cardiac muscle cell tends to divide into a “y” or “x” shape, so that it has more than two ends and joins more than two other cells, that is, it intercalates.
The fourth primary type of tissue is nerve tissue. Nerve tissue is found in the brain, spinal cord, and accompanying nerves. The function of the nerve tissue is to move and coordinate bodily functions. Nerve tissue is composed at two subtypes of tissue:1. Specialized cells called neurons (nerve cell ) receive stimuli and conduct impulses to and from all parts of the body.
2. Neuroglial or glial cells. Which is rigid, nerve tissue has a wet noodle-like compactness, and therefore must be supported by connective tissue. Some glial cells support neurons in the brain and spinal cord by entwining around them, while others bind neurons to other connective tissues.
4.3 ANALYSE BODY SYSTEMS AND ACCESS THE INTERDEPENDENCE OF THEIR FUNCTIONS.
An organ or body system is a group of organs arranged in such a way that together they perform a more complex function than can any one organ alone. The 11 major organ systems of the body are (1) integumentary, (2) skeletal, (3) muscular, (4) nervous, (5) endocrine, (6) circulatory, (7) lymphatic, (8) respiratory, (9) digestive, (10) urinary, and (11) reproductive systems. The major organs of each of the systems are
Integumentary system-skin, hair, nails, sense receptors, sweat glands, oil glands
Skeletal system-bones, joints
Nervous system-brain, spinal cord, nerves
Endocrine system-pituitary gland, pineal gland, hypothalamus, thyroid gland, parathyroids, thymus, adrenals, pancreas, ovaries, testes
Circulatory system-heart, blood vessels
Lymphatic system-lymph nodes, lymphatic vessels, thymus, spleen
Respiratory system-nose, pharynx, larynx, trachea, bronchi, lungs
Digestive system-mouth, pharynx, esophagus, stomach, intestines, rectum, anal canal, teeth, salivary glands, tongue, liver, gallbladder, pancreas, appendix
Urinary system-kidneys, ureters, bladder, urethra
Reproductive system-(male) testes, vas deferens, urethra, prostate, penis, scrotum; (female) ovaries, uterus, uterine tubes, vagina, vulva, mammary glands.
All of the organ systems of the human body affect one another. Here are more examples that illustrate the interdependence of your organ systems:
All of your organ systems are regulated by your nervous and endocrine systems – these two systems are co-directors of all of your body’s moment-to-moment activities.
Your urinary system is essential to maintaining fluid and pH balance within all of your organ systems.
Your respiratory system brings in the oxygen that your cardiovascular system delivers to all of your cells. Your respiratory system also plays a vital role in maintaining your blood pH.
Your integumentary (skin) and immune systems play critical roles in preventing life-threatening infections of all of your other organ systems.
Your muscular system allows you to move (making the rest of your organ systems relevant to your existence). Your muscular system also serves as an important reservoir for your endocrine system.
Your skeletal system provides physical protection and structural support for your other organ systems.
And the most obvious example perhaps: Your digestive system provides fuel for all of your other organ systems to use to produce energy.
2.3 GIVE EXAMPLE OF MATERIAL EXCHANGE BY DIFFERENT METHODS WITH A JUSTIFICATION OF EACH CASE.
Example of material exchange: water, carbon dioxide, oxygen
Reason or justification: Diffusion is one principle method of movement of substances within cells, as well as the method for essential small molecules to cross the cell membrane. Gas exchange in gills and lungs operates by this process. Carbon dioxide is produced by all cells as a result of cellular metabolic processes. Since the source is inside the cell, the concentration gradient is constantly being replenished, thus the net flow of CO2 is out of the cell. Metabolic processes in animals and plants usually require oxygen, which is in lower concentration inside the cell, thus the net flow of oxygen is into the cell.
Example of material exchange: water
Reason or justification
The hypertonic interstitial fluid surrounding the collecting ducts provides a high osmotic pressure for the removal of water, thus due to the difference in concentrations, water moves across the membranes of the collecting duct (which is semi-permeable) from a region of lower concentration to that of a higher one.
Example of material exchange: glucose
Method: active transport
Reason or justification
The uptake of glucose in the intestines is an example of active transport because active transport involves the transportation of things from a region of lower concentration to a higher concentration by using energy in the form of ATP.
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