Histology Question and Answer - Essay Example

Histology Question and Answer Read each question carefully. Your answers should be clear and complete and relevant to the questions asked. Use examples to support your statements. Your answers should incorporate sufficient depth of detail to indicate your thorough understanding of the topic.1. Describe how each component tissue layer in the wall of an artery (medium artery) contributes to the function of the whole vessel. Contrast the organization of a medium vein with that of a medium artery and explain why veins differ from arteries.A. All blood vessels possess a common structural pattern with variations according to the type or function.

The common pattern is the presence of three layers – the tunica intima, tunica media and the tunica adventitia from inside out. The tunica intima is the innermost layer, towards the luminal side of the blood vessel and is composed of simple, squamous endothelial cells and the supporting connective tissue. It is separated from the tunica media by the inner elastic lamina. The tunica media is composed of circular smooth muscle interspersed with connective tissue and is separated from the outermost layer by the outer elastic lamina.

The tunica adventitia is made up entirely of connective tissue. The walls of the arteries are much thicker than those of the veins as they have to carry the blood pumped by the heart to distant organs which is usually at a higher pressure. The arteries therefore comprise of more elastic tissue in the tunica intima. The medium arteries are more muscular than elastic and the internal elastic membrane is more prominent. The spiral smooth muscle cells of the tunica media assist in the propulsion of blood as well as the maintenance of the blood pressure.

The tunica adventitia is composed of collagen as well as elastic fibers and the innermost portion has an external elastic membrane. More elastic and muscular tissue in the arteries serves to sustain the vigorous systolic pressure of the blood and the maintenance of its pressure. The veins, on the other hand have thinner walls. Although they possess the basic histological structure associated with all blood vessels, the three layers are not well demarcated and blend into each other. They have lesser elastic tissue and the tunica adventitia is the thickest layer made up of collagen fibers and longitudinally oriented smooth muscle cells.

The tunica intima is modified into loose folds which form pockets or valves to resist the back flow of blood along its journey to the heart. 2. The integument fulfills several roles, including that of temperature regulation. Describe the adaptations of the integument and its derivatives that are involved in the regulation of the body temperature.The skin is a specialized layer of tissue which acts as a barrier between the outside environment and the highly sensitive internal organs of the organism.

It is made up of the thin epidermis, the outermost layer made up of stratified squamous epithelium, the much thicker middle layer, the dermis, made up of dense connective tissue and the hypodermis, which binds the skin to the underlying structures. The outermost layer of the epidermis is composed of cells which are keratinized to varying degrees in different areas of the skin, depending upon the degree of mechanical forces a specific area is likely to get exposed. The layer gets replenished by newer cells every three to four weeks.

The dermis is the layer which houses most of the specialized organelles of the skin which include capillaries carrying blood, sebaceous glands responsible for producing oil, the hair follicles and the sweat glands embedded in a rich matrix of collagen. Thermoregulation is carried out by the exchange of temperature gradient between the external environment through the rich blood supply in the capillaries as well as loss of heat by the evaporation of sweat formed by the merocrine sweat glands which are secretory tubules with their excretory ducts opening directly on the surface of the skin.

When there is excess generation of heat due to high metabolic activity within the body, either physiological or as a result of exercise, more sweat is produced which is released into the atmosphere and its evaporation allows the body to cool the blood which is then sent into the internal organs under the influence of hypothalamus in the brain.3. When cancer has been diagnosed, lymph nodes are often biopsied. Explain, in terms that a lay person would understand, why this is done. Include an explanation of the normal role and structure of a lymph node.

Lymph nodes serve as biological filters within the mammalian body which serve the vital function of filtration of harmful material like bacteria and metabolic by products and phagocytosis. They also are the site for maturation of some types of lymphocytes produced by the bone marrow. When a person suffers from a cancerous condition, the metabolic products from the cancer cells, as well as the cancerous cells travel through the blood vessels and the lymphatic channels, in a process known as metastasis, and the cells are trapped by the lymph nodes.

Lymph node biopsies therefore aid in identifying the cancerous cells when they are examined histologically. The lymph nodes are made up of network of sinuses which are supplied by the afferent lymph vessels and drained by efferent vessels in one way traffic through its fibrous septae and trabaculae. They are filled with reticuloendothelial cells and lymphocytes capable of phagocytosis. 4. Keratocytes (keratinocytes) undergo a series of changes as they age. Describe these changes and how they affect the appearance and function of the cells.

Relate the changing keratocytes to the layers of the epidermis.80% of the cells in the outermost layer of the skin, the epidermis are made of keratinocytes which are made up of stratified squamous epithelium. Their keratinization allows this layer to be tough so as to afford protection to the inner delicate layers as well as tissues. Structurally, the epidermis can be divided into five distinct layers, the stratum basale, which is a single layer of columnar/cuboidal cells which continuously divide by mitosis to generate new cells, the stratum spinosum, where the cells attain irregular polygonal structure, the stratum granulosum, in which the cellular cytoplasm is rich in keratohyalin granules and the interstitial spaces are filled with lipid material, the stratum lucidum, composed of layers of flattened dead cells with nuclear remnants and the stratum corneum, where the cellular content is full of keratin filaments and the cells are cemented together in a dense matrix of lipid.

The generation of new cells by the lowermost layer and the gradual tight packing of cells in a lipid matrix plus flattening in the upper layer imparts the protective function to the skin and the process is a continuous one, more rapid at young age and slowing down with age which results in the skin becoming thinner and prone to wrinkles as a person ages. Epidermal layer is replenished within 3 to 4 weeks at younger age and the rate falls as a person ages. The hyaluronic acid content and metabolic processes of the skin also decrease with age, which makes it more fragile. 5. There are three types of tonsils, but not all are removed during the typical tonsillectomy.

Compare the location and structure of each of the tonsils, explaining how they carry out their function. Explain also why the pharyngeal tonsils may need to be removed (and why another tonsil is not).Tonsils are specialized lymphoid tissue present at the back of the throat directly underneath the mucous membrane of the mouth cavity. They serve the function as the first line of defense against the invading pathogens due to their rich lymphocytic content. They are divided into three types based upon their location, palatine, pharyngeal and the lingual tonsils present on each side of the throat, the pharynx and below the tongue respectively.

Pharyngeal tonsils are also known as adenoids and when they get chronically inflamed, they create great stress, pain, blockade of the air passages and difficulty in deglutition. This is the reason why they are sometimes removed surgically. 6. While taking a walk with a friend, your friend steps on a rusty nail embedded in a board. The nail punctures through his flimsy shoe and impales the bottom so his foot. You help your friend to a bench, take off the shoe, and discover that your friend has a puncture wound about 3/8” across and ½” deep.

You provide the appropriate first aid (and take your friend to the emergency room for a tetanus shot). Later, at Starbucks, your friend asks you to explain how his body will respond to the injury. Your answer should reflect both a histological understanding of the immune responses and an understanding of the healing process of the integument.A deep penetrating injury with a sharp, dirty object such as a rusty nail is an immediate cause for concern as such objects usually harbor pathogens like bacteria and toxic material.

One of the notorious pathogen to enter the body is Clostridium tetani, a bacterium capable of causing widespread infection and sepsis within the body which can be life threatening. Prompt injection with the Tetanus toxoid serves to enhance the antibody formation by the body’s immune defense mechanism against this particular bacterium which results in the elimination of the organism from the body. During an injury there is an immediate perfusion of the affected area with the leucocytes and other defense cellular components like the mast cells and macrophages.

They try to engulf and phagocytose the foreign material. Reparative generative cells in the form of erythroblasts and neuroblasts are also sent to the area to regenerate the damaged tissue. The body’s humoral and cellular defense mechanisms are activated and immunoglobulins against the invading pathogens, if already present, immediately bind with the pathogen for subsequent destructive action of the phagocytes. If not already present, the host’s immune system synthesizes antibodies as a response of the antigenic stimulus provided by the pathogen.7. Describe the blood-thymus barrier and explain why it is important to isolate lymphocytes while they reside in the thymus.

The thymus is an unpaired lymphatic glandular tissue present in the form of a bilobed mass in the anterior mediastinum at birth which gradually decreases in size as a person ages. The individual lobes of the thymus are composed of the outer, dense, cortex and the inner, less dense, medulla which are enriched with lymphocytes in an epithelial framework. The thymus serves as a site for lymphocyte development and maturation by its hormonal as well storage functions. The blood-thymus barrier is formed due to the peculiar anatomical structure in the form of a network of reticular cells surrounded by capillaries in the cortex.

This serves to prevent the macromolecular substances from leaving the blood which allows the lymphocytes to stay and escape immunogenic antigens within the blood. This helps them to retain their function for action during the time of a crisis such as an infection. The thymus serves to act as a site for T lymphocyte maturation and differentiation within its protected precincts.References:Blue Histology - Integumentary System, online resource viewed October 23, 2009 at: http://www.lab.anhb.uwa.edu.au/mb140/corepages/integumentary/integum.

htmBlue Histology - Vascular System, online resource viewed October 23, 2009 at: http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Vascular/Vascular.htmLymph Nodes, online article viewed October 24, 2009 at: http://www.cayuga-cc.edu/people/web_pages/greer/biol204/lymphatic2/lymphatic2.html