ANATOMY & PHYSIOLOGY Introduction PDF

ANATOMY & PHYSIOLOGY MARIO P. OANZON, RMT, MSPH INTRODUCTION Man as a living organism may be viewed as an assemblage of minute units called cells which are marvelously integrated both structurally and functionally. Cells eventually specialize or differentiate to a greater or lesser extent. An...

ANATOMY & PHYSIOLOGY MARIO P. OANZON, RMT, MSPH INTRODUCTION Man as a living organism may be viewed as an assemblage of minute units called cells which are marvelously integrated both structurally and functionally. Cells eventually specialize or differentiate to a greater or lesser extent. An aggregate of similarly differentiated cells composes a tissue, such as fat cells of adipose tissues. Tissues in turn, form organs; organs form systems. Ultimately, systems combine in an intricate manner to create a thinking, acting human being. ANATOMY Human anatomy is the science of the shape and structure of the body and its parts. Gross anatomy deals with the macroscopic structure uncovered by dissection and visible to the unaided eye. Microscopic anatomy employs the use of the light microscope. The most detailed studies involve the methods of electron microscopy. PHYSIOLOGY Human physiology is the study of the functions of the body and its parts. Cellular physiology is the most prominent specialized branch and its concerned with the study of the activities of the individual cells and their parts. Cytology is the study of the structure and function of the individual cells. Histology is the study of tissue structure and function. Pathology is the study of abnormal or disease states in the body. Embryology is the study of the development of the fertilized egg into the mature organism. BODY FLUIDS Body fluids are found within the cells (intracellular), or outside the cells (extracellular) in the cellular spaces. The extracellular space is further divided into a vascular, or plasma compartment and an interstitial compartment (between cells). In adults plasma accounts for about 5% of the body weight; interstitial fluid, 15%; and intracellular fluid, 45%. Hence, approximately 65% of the body weight consists water, two-thirds of which is found within the cells. The remaining 35% of the body is composed of 15% protein, 5% mineral matter, and 15% fats. HOMEOSTASIS To function properly, cells require a constant environment. The environment of the body cells, the interstitial fluid medium (derived from the blood stream) immediately surrounding each cell, is called the internal environment of the body. The “steady state” concept is the condition of holding within normal ranges despite continuous change, that are maintained by coordinated physiological processes. Among the homeostatic control mechanisms are those maintaining normal concentrations of blood constituents, body temperature, volume and pH of body fluids, blood pressure and heart rate. All the homeostatic control mechanisms of the body operate by a process of negative feedback. The feedback is an informational signal that tells the driving mechanism (functional unit) how well it is doing at establishing or maintaining some variable at the desired level. Ex: if the oxygen concentration in the body fluids is too low, the information is fed back through the nervous system or hormonal stimulation to the mechanism for controlling oxygen, which automatically returns the oxygen to a higher level. The feedback is negative because it counterbalances, or negates, the change. COORDINATION OF BODY Several of the organs of the body can best be understood as homeostatic organs, since their primary function is directed toward maintenance of homeostasis; these organs include the heart, lungs, kidneys, liver, gastrointestinal tract, and skin. The coordination of maintaining balances is through internal regulating mechanisms: nervous and hormonal. The central nervous system acts as a sort of hierarchical integrator, receiving messages from its network of sensory nerves and putting out messages through its motor nerves to compensate for any detected imbalance or disturbance. The hormonal system is composed of eight major endocrine glands that secrete chemical substances called hormones. Hormones are transported in the extracellular fluids to all parts of the body to help regulate function. (ex: thyroid hormone). POSITIVE FEEDBACK Positive feedback mechanisms are not homeostatic and are rare in healthy individuals. Positive implies that when a deviation from a normal value occurs, the response of the system is to make the deviation even greater. Positive feedback therefore usually creates a cycle leading away from homeostasis and in some cases results in death. ORGANIZATION OF THE BODY Anatomic reference systems have been adopted to facilitate uniformity of description of the body. Four basic reference systems of organization are considered: direction, planes, cavities, and structural units. DIRECTION The body in anatomic position is erect, facing forward with the arms at the sides and the palms toward the front. All descriptions of location or position assume the body to be in this posture. The following diections are usually considered: Superior – uppermost or above; example, the head is superior to the neck. Inferior – lowermost or below; the foot is inferior to the ankle. Anterior – toward the front, ventral; the breast is on the anterior chest wall. Posterior – toward the back, dorsal; the vertebral column is posterior to the digestive tract. Cephalad – toward the head; the thoracic cavity lies cephalad (or superior) to the abdominal cavity. Medial – nearest the midline of the body; the ulna is on the medial side of the forearm. Lateral – toward the side; that is, away from the medial side; the radius is lateral to the ulna. Proximal – nearest the point of attachment or origin; the elbow is proximal to the wrist. Distal – away from the point of attachment or origin; the wrist is distal to the elbow. PLANES The body is also discussed with respect to planes passing through it. Midsagittal – the plane vertically dividing the body through the midline into right and left halves. Sagittal –any plane parallel to the midsagittal line vertically dividing the body into right and left portions. Horizontal (transverse) – any plane dividing the body into superior and inferior portions. Frontal (coronal) –any plane dividing the body into anterior (or ventral) and posterior (or dorsal) portions at right angles to the sagittal plane. REGIONS AND QUADRANTS OF BODY CAVITIES Cavity is a term used to describe the third organizational reference system. The body has two major cavities, each subdivided into two lesser cavities. The organs of a cavity are collectively referred to as viscera. 1. Ventral cavity A. Thoracic – pleural and pericardial cavities B. Abdominopelvic cavity 2. Dorsal cavity A. Cranial cavity B. Spinal cavity Ventral Cavity Organs of the ventral cavity are involve in maintaining a constant internal environment, or homeostasis. The Thoracic Cavity is divided into the pericardial cavity, housing the heart; and the pleural cavities, surrounding each lung. The mediastinum is a space between the pleural cavities containing, in addition to the pericardial cavity and the heart, such structures as the esophagus, trachea, thymus, great blood vessels, lymph vessels and nerves. The Abdominopelvic cavity contains those organs inferior to the respiratory diaphragm but above the urogenital diaphragm, including the kidneys, stomach, large and small intestines, spleen, liver, gall bladder, ovaries, uterus and pancreas. The Dorsal Cavity The Dorsal cavity contains structures of the nervous system serving to coordinate the body’s functions in a unified manner. It is divided into a cranial portion, containing the brain; and a spinal portion, containing the spinal cord. The term parietal refers to the walls of a cavity; for example, parietal peritoneum lines the abdominal wall. The term visceral refers to the covering of the organs; example, the visceral peritoneum covers the abdominal organs. STRUCTURAL UNITS The fourth and final system of reference is the structural unit, subdivided into cells, tissues, organs and systems. Cells All living matter is composed of cells. The basic constituent of the cell is protoplasm, an aqueous colloidal solution of protein, lipid, carbohydrate, and inorganic salts surrounded by a limiting membrane. This “ground substance of life” performs all the activities necessary to maintain life, including metabolism, respiration, digestion, assimilation, excretion, and reproduction. Tissues Tissues are composed of cells and intercellular substance, or matrix. Generally, tissues contain cells similar in appearance, functions and embryonic origin. All the diverse tissues of the body can be grouped under one of the following categories: epithelial, connective, muscle, or nervous tissue. Epithelial tissue covers surfaces, form glands, and lines most cavities of the body. It consists of one or more layers of cells with only little intracellular material. Muscle tissue is characterized by elongate cells, or fibers which generate movement by shortening or contracting in a forcible manner. Nerve tissue is composed of nerve cells forming a coordinating system of fibers connecting the many sensory and motor structures of the body. Connective tissue binds together and supports other tissues and organs. Organs An organ is composed of cells integrated into tissues serving a common function. Example: spleen, liver, heart, lungs and skin. Systems Cells are grouped together to form tissues; tissues combine to form organs. A system is a group of organs. The system is the basis for the general structural plan of the body. ORGAN SYSTEM An organ system is a group of organs classified as a unit because of a common function or set of functions. For example, the urinary system consists of the kidneys, ureter, urinary bladder, and urethra. The kidneys produce urine, which is transported by the ureters to the urinary bladder, where it is stored until eliminated from the body by passing through the urethra. LEVELS OF STRUCTURAL ORGANIZATION There are eleven major organ systems: the integumentary, skeletal, muscular, lymphatic, respiratory, digestive, nervous, endocrine, cardiovascular, urinary and reproductive. The coordinated activity of the organ systems is necessary for normal function. Because the organ systems are so interrelated, dysfunction of one organ system can have profound effects on other systems. CELL STRUCTURE 1. Cells are highly organized units containing organelles, which perform specific functions. 2. The nucleus contains genetic material, and cytoplasm is living material between the nucleus and cell membrane. Functions of the cell 1. Cells are the basic unit of life. 2. They protect and support the body, as well as provide for movement, communication, metabolism, and inheritance. Cell membrane 1. The cell membrane forms the outer boundary of the cell. It determines what enters and leaves the cell. 2. The cell membrane is composed of a double layer of phospholipid molecules in which proteins float. The proteins function as membrane channels, carrier molecules, receptor molecules, enzymes, and structural components of the membrane. Movement through the cell membrane 1. Lipid-soluble molecules pass through the cell membrane readily by dissolving in the lipid portion of the membrane. 2. Small molecules and ions can pass through membrane channels. 3. Large molecules that are not lipid-soluble can be transported through the membrane by carrier molecules. 4. Large molecules that are not lipid-soluble, particles, and cells can be transported across the membrane by vesicles. Diffusion 1. Diffusion is the movement of a solute from an area of higher concentration to an area of lower concentration within a solvent. At equilibrium, there is a uniform distribution of molecules. 2. A concentration gradient is the concentration of a solute at one point in a solution minus the concentration of that solute at another point in the solution divided by the distance between the points. Osmosis 1. Osmosis is the diffusion of a solvent (water) point across a selectively permeable membrane. 2. 0smotic pressure is the force required to prevent movement of water across a selectively permeable membrane. 3. In a hypotonic solution, cells swell (and can undergo lysis); in an isotonic solution, cells neither swell nor shrink; and in a hypertonic solution, cells shrink and undergo crenation. Filtration Filtration is the passage of a solution through a partition in response to a pressure difference. Endocytosis and Exocytosis 1. Endocytosis is the movement of materials into cells by the formation of a vesicle. Phagocytosis is the movement of solid material into cells by the formation of a vesicle. Pinocytosis is similar to phagocytosis, except that the material ingested is much smaller and is in solution. Receptor-mediated endocytosis involves cell receptors attaching to molecules that are then phagocytized by the cell. 2. Exocytosis is the secretion of materials from cells by vesicle formation. ORGANELLES Nucleus 1. The nucleus envelope consists of two separate membranes wih nuclear pores. 2. DNA and associated proteins are found inside the nucleus as chromatin. DNA is the hereditary material of the cell and controls the activities of the cell. Nucleoli and Ribosomes 1. Nucleoli consist of RNA and proteins and are the sites of ribosomal subunit assembly. 2. Ribosomes are the sites of protein synthesis. Rough and Smooth Endoplasmic Reticulum 1. Rough ER is ER with ribosomes attached. It is a major site of protein synthesis. 2. Smooth ER does not have ribosomes attached and is a major site of lipid synthesis. Golgi Apparatus The golgi apparatus is a series of closely packed membrane sacs that function to collect, modify, package, and distribute proteins and lipids produced by the endoplasmic reticulum. Secretory Vesicles Secretory vesicles are membrane-bound sacs that carry substances from the golgi apparatus to the cell membrane, where the vesicle contents are released. Lysosomes and Peroxisomes Membrane-bound sacs containing enzymes include lysosomes and peroxisomes. Within the cell the lysosomes break down phagocytized material. Peroxisomes break down fatty acids, amino acids, and hydrogen peroxide. Mitochondria Mitochondria are the major sites of ATP production, which cells use as an energy source. Mitochondria carry out aerobic respiration (requires oxygen). Cytoskeleton 1. The cytoskeleton supports the cytoplasm and organelles and is involved with cell movement. 2. The cytoskeleton is composed of microtubules, microfilaments, and intermediate filaments. Centrioles Centrioles, located in the centrosome, are made of microtubules and facilitate chromosome movement during cell division. Cilia, Flagella, and Microvilli 1. Cilia move substances over the surface of the cells. 2. Flagella are much longer than cilia and propel sperm cells. 3. Microvilli increase the surface area of cells and aid in absorption. Whole-Cell Activity The interactions between organelles must be considered for cell function to be fully understood. That function is reflected in the quantity and distribution of organelles. Cell Metabolism 1. Aerobic respiration requires oxygen and produces carbon dioxide, water, and up to 38 ATP molecules from a molecule of glucose. 2. Anaerobic respiration does not require oxygen and produces lactic acid and two ATP molecules from a molecule of glucose. Protein Synthesis 1. Cell activity is regulated by enzymes (proteins), and DNA controls enzyme production. 2. During transcriptions, the sequence of nucleotides in DNA ( a gene) determines the sequence of nucleotides in mRNA; the mRNA moves through the nuclear pores to ribosomes. 3. During translation the sequence of codons in mRNA is used to ribosomes to produce proteins. Anticodons of tRNA bind to the codons of mRNA, and the amino acids carried by tRNA are joined to form a protein. TISSUE, GLANDS AND MEMBRANES 1. A tissue is a group of cells with similar structure and function, as well as the extracellular substances located between the cells. 2. Histology is the study of tissues. Epithelial Tissue Epithelial tissue covers surfaces, usually has a basement membrane, has little extracellular material, and has no blood vessels. Functions of Epithelia General functions of epithelia include protection, permitting the passage of substances, secreting substances, and absorption of substances. Classifications of Epithelia 1. Epithelia are classified according to the number of cell layers and the shape of the cells. 2. Simple epithelium has one layer of cells, whereas stratified epithelium has more than one. 3. Pseudostratified columnar epithelium is simple epithelium that appears to have two or more cell layers. 4. Transitional epithelium is stratified epithelium that can be greatly stretched. GLANDS 1. A gland is a single cell or multicellular structure that secretes. 2. Exocrine glands have ducts, and endocrine do not. Connective Tissue 1. Connective tissue holds cells and tissues together. 2. Connective tissue has an extracellular matrix consisting of protein fibers, ground substance, and fluid. 3. Collagen fibers are flexible but resist stretching, reticular fibers form a fiber network, and elastic fibers recoil. 4. Blast cells form the matrix, cyte cells maintain it, and clast cells break it down. Functions of Connective tissue Connective tissues enclose and separate; connect tissues to one another; play a role in support and movement; store, cushion, insulate, transport, and protect. Classification of Connective Tissue 1. Embryonic connective tissue gives rise to six major categories of connective tissue. 2. Loose, or areolar connective tissue is the “loose packing” material of the body, which fills the spaces between organs and holds them in place. 3. Adipose, or fat tissue functions to store energy. Adipose tissue also pads and protects parts of the body and acts as a thermal insulator. 4. Dense connective tissue consists of matrix containing densely packed collagen fibers (tendons, ligaments, and dermis of the skin) or of matrix containing densely packed elastic fibers (elastic ligaments and in the walls of arteries). 5. Cartilage provides support and is found in structures such as the costal cartilages, disks between vertebrae, and the external ear. 6. Bone has a mineralized matrix and forms most of the skeleton of the body. 7. Blood has a liquid matrix and is found in blood vessels. Muscle tissue 1. Muscle tissue is specialized to shorten, or contract. 2. The three types of muscle tissue are skeletal, cardiac, and smooth muscle. Nervous Tissue 1. Nervous tissue is specialized to conduct action potentials (electrical signals). 2. Neurons conduct action potentials, and neuroglia support the neurons. MEMBRANE A membrane is a thin sheet or layer of tissue that covers a structure or lines a cavity. Mucous membranes Mucous membranes line cavities that open to the outside of the body (digestive, respiratory, excretory, and reproductive tracts). They contain glands and secrete mucus. Serous membranes Serous membranes line trunk cavities that do not open to the outside of the body (pleural, pericardial, and peritoneal cavities). They do not contain glands but do secrete serous fluid. Other membranes Other membranes include the cutaneous membrane (skin), synovial membrane (line joint cavities), and periosteum (around bone). INFLAMMATION Definition: Inflammation is a local response (reaction) of living vascularized tissues to endogenous and exogenous stimuli. The term is derived from the Latin "inflammare“ meaning to burn. Inflammation is fundamentally destined to localize and eliminate the causative agent and to limit tissue injury.
Thus, inflammation is a physiologic (protective) response to injury, an observation made by Sir John Hunter in 1794 concluded: “inflammation is itself not to be considered as a disease but as a salutary operation consequent either to some violence or to some diseases”.
Causes:

Causes of inflammation are apparently causes of diseases such as:
- physical agents - mechanical injuries, alteration in temperatures and pressure, radiation injuries.
- chemical agents- including the ever increasing lists of drugs and toxins.
- biologic agents (infectious)- bacteria, viruses, fungi, parasites
- immunologic disorders- hypersensitivity reactions, autoimmunity,
immunodeficiency states, etc.
- genetic/metabolic disorders- examples gout, diabetes mellitus etc…
Nomenclature:

The nomenclatures of inflammatory lesion are usually indicated by the suffix 'itis'.
Thus, inflammation of the appendix is called appendicitis and that of meninges as meningitis, etc.… However, like any rule, it has its own exceptions examples pneumonia, typhoid fever, etc….
Classification:

Inflammation is classified crudely based on duration of the lesion and histologic appearances into acute and chronic inflammation.
ACUTE INFLAMMATION

Acute inflammation is an immediate and early response to an injurious agent and it is relatively of short duration, lasting for minutes, several hours or few days.
It is characterized by exudation of fluids and plasma proteins and the emigration of predominantly neutrophilic leucocytes to the site of injury.
The five cardinal signs of acute inflammation are:
- Redness (rubor) which is due to dilation of small blood vessels within damaged
tissue as it occurs in cellulitis.
- Heat (calor) which results from increased blood flow (hyperemia) due to regional
vascular dilation
- Swelling (tumor) which is due to accumulation of fluid in the extravascular space
which, in turn, is due to increased vascular permeability.
- Pain (dolor), which partly results from the stretching & destruction of tissues due to inflammatory edema and in part from pus under pressure as in abscess cavity.
Some chemicals of acute inflammation, including bradykinins, prostaglandins and
serotonin are also known to induce pain.
- Loss of function (functio laesa): The inflammed area is inhibited by pain while severe swelling may also physically immobilize the tissue.
There are different morphologic types of acute inflammation:

1) Serous inflammation This is characterized by an outpouring of a thin fluid that is derived from either the blood serum or secretion of mesothelial cells lining the peritoneal, pleural, and pericardial cavities. It resolves without reactions. 2) Fibrinous inflammation More severe injuries result in greater vascular permeability that ultimately leads to exudation of larger molecules such as fibrinogens through the vascular barrier. Fibrinous exudate is characteristic of inflammation in serous body cavities such as the pericardium (butter and bread appearance) and pleura.
3) Suppurative (Purulent) inflammation

This type of inflammation is characterized by the production of a large amount of pus. Pus is a thick creamy liquid, yellowish or blood stained in colour and composed of:
a. A large number of living or dead leukocytes (pus cells)
b. Necrotic tissue debris
c. Living and dead bacteria
d. Edema fluid
There are two types of suppurative inflammation:
A) Abscess formation:
An abscess is a circumscribed accumulation of pus in a living tissue. It is encapsulated by a so-called pyogenic membrane, which consists of layers of fibrin, inflammatory cells and granulation tissue.
B) Acute diffuse (phlegmonous) inflammation

This is characterized by diffuse spread of the exudate through tissue spaces. It is caused by virulent bacteria (eg. streptococci) without either localization or marked pus formation. Example: Cellulitis (in palmar spaces).
4) Catarrhal inflammation

This is a mild and superficial inflammation of the mucous membrane. It is commonly seen in the upper respiratory tract following viral infections where mucous secreting glands are present in large numbers, eg. Rhinitis.
5) Pseudomembranous inflammation

The basic elements of pseudomembranous inflammation are extensive confluent necrosis of the surface epithelium of an inflamed mucosa and severe acute inflammation of the underlying tissues. The fibrinogens in the inflamed tissue coagulate within the necrotic epithelium. And the fibrinogen, the necrotic epithelium, the neutrophilic polymorphs, red blood cells, bacteria and tissue debris form a false (pseudo) membrane which forms a white or colored layer over the surface of inflamed mucosa. Inflammation 1. The function of the inflammatory response is to isolate and destroy harmful agents. 2. The inflammatory response produces five symptoms: redness, heat, swelling, pain, and disturbance of function. Chronic Inflammation Chronic inflammation results when the agent causing injury is not removed or something else interferes with the healing process. Tissue Repair 1. Tissue repair is the substitution of viable cells for dead cells. Labile cells divide throughout life and can undergo regeneration. Stable cells do not ordinarily divide but can regenerate if necessary. Permanent cells have little or no ability to divide. If killed, repair is by replacement. 2. Tissue repairs involves clot formation, inflammation, formation of granulation tissue, and the regeneration or replacement of tissues. In severe wounds, wound contracture can occur. Tissues and Aging 1. Cells divide more slowly as people age. Injuries heal more slowly. 2. Extracellular matrix containing collagen and elastic fibers become less flexible and less elastic. Consequently, skin wrinkles, elasticity in arteries is reduced, and bones break more easily. THE INTEGUMENTARY SYSTEM KEY POINTS I. Skin A. The largest organ of the body B. Composed of sweat and oil glands, nails, hair, and skin C. A system of specialized tissue 1. Glands that secrete fluids 2. Nerves that carry impulses 3. Blood vessels that assist in the regulation of body temperature D. The body’s covering E. Protector 1. A barrier against microorganisms 2. Protects the organs from injury 3. Maintains and regulates body temperature 4. Acts as a receptor for sensation (hot, cold, touch, pain) 5. Guards the deeper tissues against excessive loss of water, salts, and heat. F. Removes bodily waste products II. Three layers of the skin A. Epidermis – a thin, cellular membrane layer B. Dermis – a dense, fibrous connective tissue C. Subcutaneous tissue – a fat-containing tissue that joins the skin to the underlying muscle. Epidermis A. Outer layer of the skin. B. Cellular layer of the skin. C. Composed of epithelium – covers both the internal and external surfaces of the body. D. No blood vessels, lymphatic vessels, connective tissue, cartilage, or fat. E. Depends on the deeper dermis (or corium) layer and its network of capillaries for nourishment.  F. The deepest layer of the epidermis is the basal layer. 1. Cells in the basal layer are always growing and multiplying. 2. As basal layer cells divide, they are pushed upwards and away from the blood supply of the dermis layer by a steady stream of younger cells. 3. These cells shrink, lose their nuclei, die, and become filled with a hard protein called keratin. They are then called horny cells, reflecting their keratin composition. 4. Within 3 to 4 weeks after living as a basal cell in the deepest part of the epidermis, the horny keratinized cell is sloughed off from the surface of the skin. G. Constantly renewing itself. 1. Cells die at the same rate at which they are born. 2. As new cells rise to the surface, old cells are sloughed off.  H. Melanocytes are found in the basal layer of the epidermis. 1. Contain melanin, a black pigment. 2. The amount of melanin accounts for the color differences in skin. 3. Darker skin possesses more active melanocytes, not a greater number of melanocytes. 4. Melanin in the epidermis is vital for protection against harmful ultraviolet radiation, which can manifest as skin cancer. 5. People who are incapable of forming melanin are called albino, meaning white. a. Their skin and hair are white. b. Their eyes are red; due to the absence of pigment, the tiny blood vessels are visible in the iris. Dermis A. Second layer of the skin, the corium. B. Located just below the epidermis. C. A living tissue composed of blood, lymph vessels, and nerve fibers. D. Contains hair follicles, sweat glands, and oil glands. E. Contains connective tissue cells and fibers. F. Composed of several types of connective tissues. 1. Histiocytes – protect the body by surrounding foreign materials. 2. Fibroblasts – act to repair injury. 3. Mast cells – contain histamine, a substance released in allergic reactions that causes itching.  G. Fibers in the dermis are composed of collagen 1. “Glue”. 2. A fibrous protein material found in bone, cartilage, tendons, and ligaments, as well as the skin. 3. Tough but flexible. 4. In infants, collagen is loose and delicate, but it becomes harder as the body ages. 5. Supports and protects the blood and nerve networks that pass through the dermis. H. Hair shafts are located in the dermis. 1. Hair shafts have bundles of involuntary muscles called arrector pili attached to the hair follicles. 2. When you are frightened or cold, these muscles contract, the hair stands up, and “goose bumps” appear. Subcutaneous layer A. Made of connective tissue that specializes in the formation of fat B. Lipocytes – plentiful in the subcutaneous layer, manufacture and store large amounts of fat C. Important in protecting the deeper tissues of the body D. Acts as a heat insulator E. Connects the dermis to the muscles and organs below it F. Fat tissue insulates the inner structures from temperature extremes Sebaceous glands A. Produce an oily secretion called sebum. B. Carried to the edges of the skin by ducts and excreted through openings in the skin called pores. C. Lubricates the skin. D. Closely associated with hair follicles; their ducts open into the hair follicle. E. Influenced by sex hormones. 1. Causes them to be over active at puberty. a. Excess oil production of the skin at puberty. 2. Causes them to be underactive in old age. a. Drying of skin as we age. Sudoriferous glands A. Tiny coiled glands found on almost all body surfaces. B. Produce a watery solution called sweat. 1. Helps cool the body. 2. Carried to the edges of the skin by ducts and excreted through openings in the skin called pores. 3. Perspiration (sweat) is almost pure water, dissolved materials such as salt making up less than 1%. 4. Colorless and odorless. 5. The odor produced when sweat accumulates is due to the actions of bacteria. C. Certain sweat glands, only active from puberty onward, are larger than ordinary sweat glands.  D. Ceruminous glands are classified as modified sweat glands 1.Found in the ear canal. 2. Produce a yellow waxy substance called cerumen (ear wax). E. Diaphoresis 1. Comes from the Greek dia, meaning “through,” and phoreo meaning “I carry”. 2. “The carrying through of perspiration”. 3. Perspiration, especially when copious and medically induced.  Hair A. Composed of a network of horny cells. B. Hair growth is similar to the growth of the skin’s epidermal layer. C. Deep-lying cells in the hair roots move forward through the hair follicles (or shafts) that hold the hair fiber. D. Melanocytes located at the root of the hair follicles supply the melanin pigment for the hair fiber. E. Hair color depends on the amount of melanin present. F. Because hormone production decreases as we get older, hair loses color and become transparent (gray). Nails A. Harder keratin plates that cover the dorsal surface of the last bone of each toe and finger. B. Composed of horny cells that are cemented together and can extend indefinitely until cut or broker. C. Nails grow in thickness and length by the division of the cells of the nerve root at the base of the nail plate. D. Grow approximately 1mm a week. E. May re-grow completely in 3-5 months. F. Toenails grow more slowly than do fingernails. Cancerous Lesions A. Basal cell carcinoma (BCCA) 1. Malignant tumor of the basal cell layer of the epidermis. 2. The most frequent type of skin cancer. 3. Slow-growing tumor of the basal layer of the epidermis. 4. Usually occurs on the upper half of the face, near the nose, and is non-metastasizing. B. Squamous cell carcinoma (SCCA) 1. Malignant tumor of the squamous epithelial cells of the epidermis. 2. The tumor may grow in places other than the skin – wherever squamous epithelium is found (mouth, larynx, bladder, esophagus, etc.). 3. It may arise from actinic (sun-related) keratoses and metastasize to the lymph nodes. 4. The treatment for both basal and squamous cell carcinomas is surgical excision or radiation therapy. C. Malignant melanoma 1. Cancerous tumor composed of melanocytes. 2. Tumors often metastasize into the lungs, liver, and brain after arising in areas of the body where pigmented cells occur. 3. Treatment includes excision of the tumor, regional lymphadenectomy and chemotherapy to prevent metastases. D. Mycosis fungoides 1. A rare, chronic skin disease caused by the infiltration of malignant lymphocytes. 2. Characterized by generalized erythroderma and large reddish raised areas (tumors) that spread and ulcerate. 3. Treatment with topical nitrogen mustard and radiation can be effective in controlling the disease. SKELETAL SYSTEM