Anatomy Essay, Research Paper
?Overview of Anatomy & Physiology?
Anatomy – is the study of the structure of the body parts & their
relationship to one another.
Physiology – concerns with the function of the body?s structural
machinery – how the body works.
Topics of Anatomy
Gross Anatomy – is the study of the large body structures visible to the
naked eye. It can be approached in different ways.
Regional Anatomy – is the study of all the structures in one particular
region.
Systematic Anatomy – is when anatomy is studied system by system.
Surface Anatomy – is the study of the internal structures as they relate
to the overlying skin surface.
Microscopic Anatomy – is the study of structures too small to be seen
without a microscope.
Topics of Physiology
They are usually divided into operations of specific organ systems.
The Principle of Complementarity of structure & Function – Anatomy &
Physiology are taught together because the functions always reflect the
structure.
Levels of structural organization
Chemical level – this includes atoms & molecules.
Cellular level – is the smallest unit of living things.
Tissue level – are groups of similar cells that have a common function.
Organ level – an organ is at least two tissues that perform a specific
function of the body.
Organ System level – organs that work together to accomplish a
specific function.
Homework (pgs. 4-5) February 5,1999
?Summary of the Body?s Organ Systems?
Integumentary System – forms of the external body covering; protects
deeper body tissue from injury; synthesizes vitamin D; site of
cutaneous (pain, pressure, ect.) receptors, & sweat & oil glands.
Skeletal System – protects & supports body organs; provides the
framework the muscles use to cause movement; blood cells are formed
within bones; stores minerals.
Muscular System – allows manipulation of the environment,
locomotion, & facial expression; maintains posture; produces heat.
Nervous System – fast-acting control system of the body; responds to
internal & external changes of the body by activating appropriate
muscles & glands.
Endocrine System – glands secrete hormones that regulate processes
such as growth, reproduction, & nutrient use (metabolism) by body
cells.
Cardiovascular System – Blood vessels transport blood, which carries
oxygen, carbon dioxide, nutrients, ect.; the heart pumps blood.
Lymphatic System/Immunity – Picks up fluids leaked from blood
vessels & returns it to the blood; disposes of debris in the lymphatic
stream; houses white blood cells (lymphocytes) involved in immunity.
The immune response mounts the attack against foreign substances
within the body.
Respiratory System – keeps blood constantly supplied with oxygen &
removes carbon dioxide; the gaseous exchange occurs through the
walls of the air sacs of the lungs.
Digestive System – breaks down food into absorbable units that enter
the blood for distribution to the body cells; indigestible foodstuffs are
eliminated as feces.
Urinary System – eliminates nitrogenous waste from the body;
regulates water, electrolytes, & the acid-based balance in the blood.
Male Reproductive System – overall function is the production of
offspring. Testes produce sperm & male sex hormones; ducts & glands
aid in delivery of sperm to the female reproductive tract.
Female Reproductive System – overall function is the production of
offspring. Ovaries produce eggs & female sex hormones; remaining
structures serve as sites for fertilization & the development of the
fetus. Mammary glands of female breast produce milk to nourish the
newborn.
Classwork (pgs. 6-8) February 8, 1999
?Maintaining Life?
Necessary Life Functions
Maintaining Boundaries – keeps its internal environment separate
from the external environment (ex.- skin or cell membrane).
Movement – all activities promoted by the muscular system; on the
cellular level, muscle cells contracting is called contractility.
Responsiveness – irritability is the ability to sense changes in the
environment & then respond to them.
Digestion – is the process of braking down ingested food into simple
molecules that can be absorbed into the blood.
Metabolism – all chemical reactions that occur within the body.
Excretion – is the process of removing wastes from the body; usually
refers to urine.
Reproduction – the making more of an organism; occurs asexually
(one) or sexually (two).
Growth – an increase in size.
Survival Needs
The goal of the body system is to maintain life. There are several factors
that need to be present, like:
Nutrients – these contain the chemical substances used for energy &
cell building.
Oxygen – chemical reactions in the body require oxygen.
Water – is the single most abundant substance in your body.
Homeostasis
Homeostasis – is the body?s ability to maintain a relatively stable internal
condition, even though the outside world changes. There are three factors
in the homeostatic control organism:
Receptor – sensor that monitors the environment.
Control Center – analyzes input it receives & determines the
appropriate action.
Effector – provides the means to the response.
Classwork (pgs. 8-13, & 16) February 9, 1999
?Positive & Negative Feedback?
Most of the homeostatic control mechanisms are negative feedback
mechanisms. The net effect is that the output of the system shuts off the
original stimulus (ex.- heat & air conditioning in houses & glucose
regulating {pgs. 9 -10, fig. 1.5}).
Positive feedback mechanisms, (often referred to as cascades) the result
or response enhances the original stimulus so that the output (activity) is
accelerated {pg. 11, fig. 1.6}.
Regional Terms
Used to designate specific areas within the major body divisions.
Axial – part that makes up the main axis of the body; head, neck, &
truck.
Appendicular – part that consists of the appendages or limbs; arms &
legs.
Body Planes
In the study of Anatomy, the body is often sectioned along a flat surface
called a plane. A section is named for the plane along which it is cut.
Sagittal plane – a vertical plane that divides the body into left & right
halves.
Median or Midsagittal plane – a vertical plane that lies directly in the
center (midline) of the body
Frontal or Coronal plane – a vertical plane that divides the body into
anterior & posterior parts.
Transverse or Horizontal plane – a horizontal plane that divide the
body into superior & inferior parts; also called a cross section.
Body Cavities
Within the axial portion of the body are two large cavities. They are closed
to the out side & each contains internal organs.
Dorsal Body Cavity – contains two divisions.
Cranial cavity – within which the brain is encased by the skull.
Vertebral or Spinal cavity – runs within in the bony vertebral &
encloses the spinal cord.
Ventral Body Cavity – contains two divisions.
Thoracic cavity – surrounded by the ribs.
Pleural cavities – each houses a lung, & the medial mediastinum.
Pericardial cavity – within the mediastinum, encloses the
heart, & surrounds the thoracic organs (esophagus, trachea,
ect.)
Abdominopelvic cavity – a dome-shaped muscle important in
breathing.
Abdominal cavity – contains the stomach, spleen, liver,
intestines, & other organs.
Pelvic cavity – contains the bladder, rectum, & reproductive
organs.
Homework (pgs. 11-12, & 14) February 9, 1999
?Homeostatic Imbalance?
Homeostasis is so important that most disease is regarded as a result of
its disturbance, a condition called homeostatic imbalance. As we age, our
body organs & control systems become less efficient. As a result, our
internal environment becomes less & less stable. These events place us at
an even greater risk for illness & produce the changes we associate with
aging.
Another important source of homeostatic imbalance occurs in certain
pathological situations when the usual negative feedback mechanisms are
overwhelmed & destroyed by the positive feedback mechanisms take over.
Some instances of heart failure reflect this phenomenon.
?Anatomical Position & Directional Terms?
To describe body parts & position accurately, we need an initial reference
point & must use indications of direction. The anatomical reference point
is a standard body position called anatomical position. In this position,
the body is erect with feet together. The terms ?right? & ?left? refer to those
sides of the cadaver or the person being viewed – not to those of the
observer.
Directional terms allow us to explain exactly where one body structure is
in relation to another. Anatomical terminology saves words & is less
ambiguous; anatomical meanings are very precise.
Orientation & Directional Terms
Superior (cranial) – toward the head end or upper part of a structure
or the body; above. Example: The head is superior to the abdomen.
Inferior (caudal) – away from the head end or toward the lower part of
a structure or the body; below. Example: The navel is inferior to the
chin.
Anterior (ventral) – toward or at the front of the body; in front of.
Example: The breastbone is anterior to the spine.
Posterior (dorsal) – toward or the back of the body; behind. Example:
The heart is posterior to the breastbone.
Medial – toward or at the midline of the body; on the inner side of.
Example: The heart is medial to the arm.
Lateral – away from the midline of the body; on the outside of.
Example: The arms are lateral to the chest.
Intermediate – Between a more medial & more lateral structure;
Example: The collarbone is intermediate between the breastbone & the
shoulder.
Proximal – Closer to the origin of the body part or the point of
attachment of a limb to the body trunk. Example: The elbow is proximal
to the wrist.
Distal – farther from the origin of the body part or the point of
attachment of a limb to the body trunk. Example: The knee is distal to
the thigh.
Superficial – Toward or at the body surface. Example: The skin is
superficial to the skeletal muscles.
Deep – away from the body surface; more internal. Example: The lungs
are deep to the skin.
Classwork (pg. 17) February 10, 1999
?Body Cavities & Membranes?
Membranes in the Ventral Body Cavity
The walls of the ventral body cavity & the outer surfaces of the organs it
contains are covered by serous membrane. The one lining the cavity wall
is the parietal serosa, which folds on itself to form the visceral serosa {pg.
17, fig. 1.10} for all the cavities.
Other cavities
Oral & Digestive cavity – oral cavity, commonly called the mouth
Nasal cavity – located within & posterior to the nose.
Orbital cavities – house the eyes & present them in an anterior
position.
Middle Ear cavities – carved into the temporal bone of the skull lie just
medial to the eardrum; contain tiny bones that transmit sound
vibrations.
Synovial cavities – are joint cavities; enclosed within fibrous capsules
that surround freely movable joints of the body (ex.- elbow & knee
capsules).
Classwork (pgs. 109-113, 119,132, 134 ) February 12, 1999
?Types of Tissues?
Histology is the study of tissues, it complements the study of gross
anatomy. Tissues are groups of cells that are similar in structure &
perform a common function. Tissues are organizations of similar cells
that are surrounded & often embedded in a nonliving intercellular material
called a matrix.
Four Principle Types of Tissues
Epithelial tissue – is a sheet of cells that covers & protects the body
surface; lines body cavities; moves substances in & out of the blood; &
forms some glands.
Connective tissue – supports the body & connects body parts; found
everywhere in the body.
Muscle tissue – produce most types of body movement.
Nervous tissue – most complex body tissue; specializes in
communication between various parts of the body.
Functions of the Epithelial Tissue
Protection – the skin protects the body from mechanical, chemical, &
invading bacteria.
Sensory Functions – skin, nose, eyes. & ears.
Excretion – found in the lining of the kidneys tubule makes it possible.
Filtration – also in kidneys; filters blood so it can be excreted.
Secretion – secretes hormones, mucus, digestive juices, & sweat.
Absorption – found in the lining of the gut & respiratory tract. This
allows for absorption of nutrients from the gut; & exchange of gases
between the lungs & heart.
Classification of Epithelia
Each epithelium is given two names. The first name indicates the # of cell
layers present; the second describes the shape of its cells.
Simple Epithelia
The simple epithelia are concerned with absorption, secretion, & filtration.
Protection is not one of their specialties.
Simple Squamous Epithelium – their cells are flattened laterally & their
cytoplasm is spares; in a surface view, it resembles a tiled floor,
perpendicularly they resemble fried eggs. This epithelium is found were
filtration or the exchange of substances by rapid diffusion is a priority.
Simple Cuboidal Epithelium – consists of a single layer of cubical cells &
its spherical nuclei is stained darkly; looks like a string of beads when
viewed microscopically. It functions are excretion & absorption.
Simple Columnar Epithelium – seen a as a single layer of tall, closely
packed cells, aligned like soldiers in a row. Mostly associated with
absorption & secretion. It lines the digestive tract from the stomach to
the rectum.
Pseudostratified Columnar Epithelium – cells vary in height & rest on
the basement membrane, but only the tallest reach the apical surface
of the epithelium; the nuclei are located at different levels above the
basement, thus giving a false (pseudo) impression. They secrete &
absorb substances.
Homework (pgs. 109-110) February 12, 1999
?Special Characteristics of Epithelium?
Epithelial tissues have many characteristics that distinguish them from
other tissues types.
Cellularity. – Epithelial tissue is composed almost entirely of
close-packed cell. Only a tiny amount of extracellular material lies in
the narrow spaces between them.
Specialized contacts. – Epithelial cells fit closely together to form
continuous sheet. Adjacent cells are bound together at many points by
lateral contacts, including tight junctions & desmosomes.
Polarity. – All epithelia have an apical surface, a free surface exposed
to the body exterior or the cavity of an internal organ, & an attached
basal surface. All epithelia exhibit polarity, meaning that cells near the
apical surface differ from those at the basal surface in both structure &
function.
Although some apical surfaces are smooth & slick, most have
microvilli, finger like extensions of the plasma membrane. Microvilli
tremendously increase the exposed surface area, & in epithelia that
absorb or secrete substances, the microvilli are often so dense that the
cell apices have a fuzzy appearance called a brush border. Some
epithelia, such as that lining the trachea, have motile cilia that propel
substances among their surfaces.
Lying adjacent to the basal surface of an epithelium is a thin
supporting sheet called the basal lamina. This noncellular, adhesive
sheet consists largely of glycoproteins secreted by the epithelial cells.
Functionally, the basal lamina acts as a selective filter; that is, it
determines which molecules diffusing from the underlying connective
tissue will be allowed to enter the epithelium. The basal lamina also
acts as a scaffolding along which epithelial cells can migrate to repair a
wound.
Supported by connective tissue. – All epithelial sheets rest upon & are
supported by connective tissue. Just deep to the basal lamina is the
reticular lamina, a layer of extracellular material containing a fine
network of collagen protein fibers that ?belong to? the underlying
connective tissue. Together the two laminae form the membrane
basement. The basement membrane reinforces the epithelial sheet,
helping it to resist stretching & tearing forces, & defines the epithelial
boundary.
An important characteristic of cancerous epithelial cells is their
failure to respect this boundary, which they penetrate to invade the
tissue beneath.
Innervated but avascular. – Although epithelium is innervated (supplied
by nerve fibers), it is avascular (contains no blood vessels). Epithelial
cells are nourished by substances diffusing from blood vessels in the
underlying connective tissue.
Regeneration. – Epithelium has a high regenerative capacity. Some
epithelia are exposed to friction & their surface cells removed by
abrasion. Others are damaged by hostile substances in the external
environment (bacteria, acid, smoke). As long as epithelial cells receive
adequate nutrition, they can replace lost cells rapidly by cell division.
Classwork (pgs. 115-118) February 16, 1999
?Stratified & Glandular Epithelia?
Stratified Epithelia
Stratified epithelia consists of two or more cell layers.
Stratified Squamous Epithelium – is the most widespread of the
stratified; found in the exterior part of the skin.
Stratified Cuboidal & Stratified Columnar – are rare; usually found in
large ducts & some glands.
Transitional Epithelium – found in the lining of urinary organs.
Transitional epithelium can change shape in order to stretch.
Glandular Epithelia
Epithelium of the glandular type is specialized for secretory activity. All
glands are classified as exocrine or endocrine.
Exocrine glands – discharge their secretory products into ducts (ex.
salivary glands)
Endocrine glands – are ductless; they discharge their secretions
directly: hormones.
Multicellular exocrine glands have two structural elements: ducts &
secretory units. On the basis of their duct structures they are either
simple glands – single unbranched ducts or compound glands – that have a
branched duct. Then they are further described according to their
secretory parts:
Tubular – forms tubes.
Alveolar – small flask like sacs.
Tubuloalveolar – both.
Functional Classifications of Exocrine Glands.
Methods by which they discharge. Three types:
Apocrine Glands – collect their products near the tips of the cell & then
they release into a duct by pinching of (ex. mammary glands).
Holocrine Glands – collect inside the cells & then they rupture (ex.
sedaceous (oil) glands).
Merocrine Glands – discharge directly through the cell membrane (ex.
salivary glands).
Homework (pgs. 119) February 16, 1999
?Unicellular Exocrine Glands?
Unicellular exocrine glands are single cells scattered in am epithelial sheet
amid cells with other functions. They have no ducts. In humans, all such
glands produce mucin, a complex glycoprotein that dissolves in water
when secreted. Once dissolved, mucin forms mucus, a slimy coating that
both protects & lubricates surfaces. The only important unicellular glands
in humans are the goblet cells found sprinkled in the columnar epithelium
cells lining the intestinal & respiratory tracts. Although unicellular glands
probably outnumber multicellular glands, unicellular glands are the less
well known of the two glands types.
Classwork (pgs. 119, 122-126) February 17, 1999
?Connective Tissue?
Connective Tissue is the most abundant tissue. Its major functions are:
Binding & Support
Protection
Insulation & Blood
Transportation
Common Characteristics of Connective Tissue
Common origin – derived from the mesoderm.
Degrees of vascularity; some are vascularized, others are not.
Extracellular matrix – this separates the living cells of the tissue.
Two Classes of Connective Tissue
The first is divided into four groups.
Loose Ordinary Tissue (Areolar) – found between other tissues or
other organs; used in connection; it is a fluid.
Adipose Tissue (Fat) – found under the skin & as padding at various
points. Used for protection, insulation, & a reserve for food.
Reticular Tissue – slender branching of reticular fibers forms the
framework for the spleen, lymph nodes, & bone marrow; look like
little strings that run in all directions.
Dense Fibrous Tissue – tendons & ligaments; they are bundles or
callagenous fibers in parallel rows in a fluid matrix; they are thicker
strings that run in one direction.
The second class of connective tissue contains cartilage – has qualities
intermediate between dense fibrous connective tissue & bone. It is
avascular (no bloods
Hyaline Cartilage – is the most abundant tissue type in the body;
provides firm support with some pliability.
Elastic Cartilage – nearly identically like hyaline cartilage, but has
more elastin fibers which gives this tissue a greater tolerance for
repeated bending.
Fibrocartilage – (fibrous cartilage) often found where hyaline
cartilage meets a true ligament or tendon. Found where strong
support & ability to withstand heavy pressure are required.
Homework (pgs. 120-122) February 17, 1999
?Structural Elements of Connective Tissue?
Connective tissues have three main elements: ground substance, fibers, &
cells. Ground substances make up the extracellular matrix. (Note: that the
term matrix indicates the ground substance.)
Ground Substance
Ground Substance – is an amorphous (unstructured) material that fills the
space between the cells & contains the fibers. It is composed of instertitial
fluid, cell adhesion proteins, & proteoglycans. Cell adhesion proteins, a
group that includes fibronectin & lamina, sever mainly as a connective
tissue glue that allows connective tissue cells to attach themselves to
matrix elements. The proteoglycans consists of a protein core to which
glycosaminoglycans (GAGs) are attracted. The strand-like GAGs which are
large, negatively charged polysaccharides, stick out from the core protein
like the fibers of a bottle brush. Important examples of GAGs in
connective tissues are chondroitin sulfate, keratan sulfates, & hyaluronic
acid. The GAGs intertwine & trap water, forming a substance that varies
from a fluid to a semi-stiff hydrated gel. The relative amounts & kinds of
GAGs help determine the properties of the matrix. Example – The higher
the GAG content, the stiffer the ground substance is.
The ground substance holds fluids & functions as a molecular sieve, or
medium, through which nutrients & other dissolved substances can diffuse
between the blood capillaries & the cells. The fibers embedded in the
ground substance makes it less pliable & impede diffusion somewhat.
Fibers
The fibers of the connective tissue provide support. Three types of fibers
are found in connective tissue matrix:
Collagen Fibers – (white fibers), are constructed primarily of the
fibrous protein collagen. Collagen molecules are secreted into the
extracellular space, where the are assembled spontaneously into
cross-linked fibers. Collagen fibers are extremely tough & provide high
tensile strength to the matrix. Stress test show that collagen fibers are
stronger than steel fibers of the same size. Collagen fibers are the
most abundant.
Elastic Fibers – (yellow fibers), are formed largely from another fibrous
protein, elastin. Elastin has a randomly coiled structure that allows it
to stretch & recoil like a rubber band. The presence of elastin in the
matrix gives it a rubbery, or resilient, quality. Connective tissue can
stretch only so much before its thick, rope-like collagen fibers become
taut. Then, when the tension lets up, elastic fibers snap the connective
tissue back to its normal length & shape. Elastic fibers are found where
greater elasticity is needed (ex. skin, lungs, & blood vessel walls).
Reticular Fiber – are fine callagenous fibers & are continuous with
collagen fibers. They branch extensively, forming delicate networks
that surround small blood vessels & support the soft tissue of organs.
They are particularly abundant where connective tissue abuts other
tissue types, for example, in the basement membranes of epithelial
tissues, & around capillaries, where they form fuzzy ?nets.?
Cells
Each major class of connective tissue has a fundamental cell type that
exists in immature & mature forms. The undifferentiated cells, indicated
by the suffix blast, are actively mitotic cells that secrete the ground
substance & the fibers characteristics of their particular matrix. The
primary blast cell types by connective tissue class are:
Connective tissue proper: fibroblast.
Cartilage: chondroblast.
Bone: osteoblast.
Blood: hemocytoblast or hematopoietic stem cell.
Once they synthesize the matrix, the blast cells assume their less active,
mature mode, indicated by the suffix cyte. The mature cells maintain the
health of the matrix. However, if the matrix is injured, they can easily
revert to their more active state to repair & regenerate the matrix. (The
hemocytoblast, the blood-forming stem cell found in bone marrow, always
remains actively mitotic.)
Additionally, connective tissue is home to an assortment of other cell
types, such as nutrient-storing fat cells & mobile cells that migrate into the
connective tissue matrix from the bloodstream. The latter include white
blood cells (neutrophils, eosinophils, lymphocytes) & other cell types
concerned with tissue response to injury, such as mast cells,
macrophages, & antibody-producing plasma cells. This wide variety of
cells is particularly obvious in our prototype, areolar connective tissue.
The oval mast cells are typically found clustered in tissue spaces deep to
an epithelium or along blood vessels. These cells act as sensitive sentinels
to detect foreign substances (ex, bacteria, fungi) & initiate local
inflammatory responses against them. In the mast cell cytoplasm are
conspicuous secretory granules containing:
Heparin – an anticoagulant (a chemical that prevents the blood clotting)
when free in the bloodstream, but its significance in human mast cells
is uncertain
Histamine – is released during inflammatory reactions, makes the
capillaries leaky.
Macrophages are large, irregularly shaped cells that avidly phagocytize a
broad variety of foreign materials, ranging from foreign molecules to
entire bacteria to dust particles. Macrophages also engulf & dispose of
dead tissue cells, & they are central actors in the immune system. In
connective tissues, they may be attached to connective tissue fibers or
they may migrate freely through the matrix. Macrophages are peppered
throughout loose connective tissue, bone marrow, & lymphatic tissue.
Those in certain sites are given specific names. They are called histiocytes
in loose connective tissue, Kupffer cells in the liver, & microglial cells in the
brain. Although all these cells are phagocytes, some have selective
appetites. For example, macrophages of the spleen primarily dispose of
aging red blood cells, but they will not turn down other ?delicacies? that
come their way.
Classwork (pgs. 128-134) February 18, 1999
?Bone, Blood, Membranes, Nervous, & Muscle Tissues?
Bone (osseous) – due to its rock hardness it has the ability to support
& to protect softer tissue.
Blood – the fluid within blood vessels; functions as the transport vehicle
in the cardiovascular system.
Membranes – a continuous multicellular sheet composed of at least
two primary tissue types: an epithelium bound to an underlying layer of
connective tissue proper.
Cutaneous Membranes – are your skin.
Mucous Membranes – lines cavities open to the exterior.
Serous Membranes – are moist membranes found in closed ventral
body cavities (ex. pericardium, pleura).
Nervous Tissue – Has two major cell types.
Neurons – specialized cells that generate & conduct nerve
impulses.
Neuralgia – are supporting cells.
Muscle Tissue – made up of muscle fibers. Muscle cells possess
mylofilaments.
Skeletal Muscle – attached to bone, voluntary or stratified (lines);
form the flesh of the body.
Cardiac Muscle – occurs in the heart, it is striated & contains
intercalated discs ( junctions of branching cells).
Smooth Muscle – visceral or involuntary; found in hallow internal
organs.
Homework (pgs. 136) February 18, 1999
?Steps of Tissue Repair?
Tissue repair requires that cells divide & crawl, activities that are initiated
by growth factors (wound hormones) released by injured cells. It occurs in
two major ways: by regeneration – the replacement of destroyed tissue
with the same kind of tissue- & by fibrosis – involves proliferation of
fibrous connective tissue called scar tissue. Each of these occurs depends
on:
The types of tissue damaged.
The severity of the injury.
In skin, the tissue we will use as our example, repair involves both
activities.
Inflammation sets the stage. The process begins while the
inflammatory reaction is still going on. Let us briefly examine what has
happened up to this point. Tissue injury sets the following
inflammatory events into motion. First, because of the release of
histamine & other inflammatory chemicals by injured tissue cells,
macrophages, mast cells, & others, the capillaries dilate & become very
permeable. This allows white blood cells & plasma fluid rich in clotting
proteins, antibodies, & other substances to seep into the injured area.
Then the leaked clotting proteins construct a clot, which stops the loss
of blood, holds the edges of the wound together, & effectively walls off,
or isolates, the injured area, preventing bacteria, toxins, or other
harmful substances from spreading to surrounding tissues. The
portion of the clot exposed to the air quickly dries & hardens, forming a
scab. The inflammatory events leave excess fluid, bits of destroyed
cells, & other debris in the area. Most of this material is essentially
removed from the area via lymphatic vessels or phagocytized by
macrophages. At this point, the first step of tissue repair,
organization, begins.
Organization restores the blood supply. During organization the
temporary blood clot is replaced by granulation tissue. Granulation
tissue is a delicate pink tissue composed of several elements. Thin,
extremely permeable capillaries bud from intact capillaries nearby &
enter the damaged area, laying down a new capillary bed; they
protrude nub-like from the surface of the granulation tissue, giving it a
granular appearance. These capillaries are fragile & breed freely, as
demonstrated when someone ?picks at? a scab. Also present in
granulation tissue are scattered macrophages & fibroblasts that
synthesize new collagen fibers to bridge the gap permanently. As
organization continues, macrophages digest & remove the original
blood clot. The granulation tissue, destined to become scar tissue (a
permanent fibrous tissue patch), is highly resistant to infection
because it produces bacteria-inhibiting substances.
Regeneration &/or fibrosis effects permanent repair. While
organization is going on, the surface epithelium begins to regenerate.
Epithelial cells migrate across the granulation tissue just beneath the
scab, which soon detaches. As the fibrous tissue beneath matures &
contracts, the regenerating epithelium thickens until it finally
resembles than of the adjacent skin. The end result is a fully
regenerated epithelium, & an underlying region of scar tissue. The scar
may be invisible, or visible as a white thin line, depending on the
severity of the wound.
Classwork (pgs. 189-203) February 24, 1999
?Skeletal System?
The adult Skeleton has 206 separate bones. There are two main divisions:
Axial Skeleton – has 80 bones; the upper axis has 74; the inner ear has
6. Contains the skull. There are two major divisions:
Cranium – brain case (has 8 bones):
1. Frontal Bone – forehead.
2./3. Parietal Bones – bulging top side of the cranium.
4./5. Temporal Bones – house the middle & inner ear structures.
6. Occipital Bone – creates the framework of the lower back part
of the skull.
7. Sphenoid Bone – resembles bat wings.
8. Ethmoid Bone – forms bony area between the nasal cavity &
the orbits of the eyes.
Face – (has 14 bones):
1./2. Maxillae Bones – upper jaw (upper lip); one on each side.
3. Mandible Bone – lower jaw.
4./5. Zygomatic Bones – cheeks
6./7. Nasal Bones – bridge of the nose; one on each side.
8./9. Lacrimial Bones – helps form tear ducts.
10./11. Inferior Nasal Conchae Bones – ledge protecting the nasal
cavity.
12. Vomer Bone – completes the nasal septum.
13./14. Palatine Bones – hard plate within the mouth.
Appendicular Skeleton – consists of 126 bones.
Classwork (pgs. 204-213) February 25, 1999
?Regions of the Spinal Column?
Hyoid Bone – is below the skill, attached to the bottom of the tongue;
single bone in the neck above the larynx & below the mandible; not
attached to any other bone in the body (sesamoid).
Spinal Column; divided into three types of vertebrae:
Cervical Vertebrae – neck (has 7 bones).
Thoracic Vertebrae – found in the posterior part of the chest or the
thorax (has 12 bones).
Lumbar Vertebrae – found in the small of the back (has 5 bones).
Sacrum – below the vertebral column, a single bone resulted by a fusion
of 5 separate vertebrae.
Atlas – is at the top of the vertebral column, the head sits upon it; has no
body & no spinous processes
Axis – is below the atlas; has a body & a spinous processes.
Coccyx – is below the sacrum, consists of 4 bones fused together (is a tail
bone).
Sternum – is the media part of the anterior chest.
Ribs – 12 pairs or 24; in front (anterior), each of the first 7 ribs joins a
costal cartilage that attach to the sternum. Then the next 3 join the
cartilage of the ribs before, so they are attached to the sternum directly.
The 11th & 12th pairs do not attach & are called floating ribs.
Classwork (pgs. 214-227) February 26, 1999
?Appendicular Skeleton?
Bones of the limbs & their girdles are collectively called the appendicular
skeleton because they are appended to the axial skeleton that forms the
longitudinal axis of the body.
Pectoral (Shoulder) Girdle
Shoulder Girdle – consists of two bones, the anterior clavicle & the
posterior scapula.
Clavicles – collar bones, are slender, doubly curved long bones that can
be felt along their entire courses as they extend horizontally across the
superior thorax.
Scapulae – shoulder blades, are thin, triangular flat bones.
The Upper Arm
Humerus – (arm) articulates proximally with the scapula at the shoulder, &
distally with the radius & ulna at the elbow.
Radius – on the thumb side, has two proximal articulations, the humerus,
& ulna.
Ulna – on the little finger side, articulates proximally with the humerus &
the radius, & distally with cartilage.
7 carpals – wrist.
5 metacarpals- framework of the hand.
14 phalanges – fingers.
Pelvic (Hip) Girdle
Hip Girdle- formed by a pair of coxal bones, which consists of three bones,
which are separate during childhood & fused together during adulthood):
Ilium – the large flaring bone that forms a major portion of a coxal
bone.
Ischium – forms the posteroinferior part of the hip bone.
Pubis – forms the anterior portion of the os coxa.
The Lower Limb
Femur – (thigh bone), is the largest, longest, & strongest bone in the body.
Tibia – the longest & strongest bone in the lower leg; articulates proximally
with the femur, & distally with the fibula & talus.
Fibula – is smaller & more deeply placed, proximally articulates with the
tibia.
7 tarsal – ankles.
5 metatarsals – flat part of the foot.
14 phalanges – toes.
Classwork (pgs. 261-262) March 05, 1999
?General Function of the Muscular System?
There are four general functions of the skeletal system.
Movement – either body as a whole or parts of the body.
Heat Production – muscles produce heat — since there are so many
muscles, they are one of the most important parts of the mechanisms
for maintaining homeostasis.
Posture – continual partial contraction of muscles allow for standing,
sitting, ect.
Stabilizing Joints – muscles help keep everything in place.
There are four characteristics that enable skeletal muscle tissue to
function:
Excitability – the ability to be stimulated, this causes them to be able to
respond to regulatory mechanisms, such as nerve signals.
Contractility – the ability to shorten, which allows muscles to pull on
bones & produces movement.
Extensibility – the ability to stretch & return to the resting length.
Elasticity – the ability of the muscle fiber to resume to its resting length
after being stretched.
Skeletal muscle cells, are composed of bundles of skeletal muscle fibers
that extend the length of the muscle. They are long cells. They have the
same structural parts as other cells, but they have different names:
Sarcoma – cell membrane.
Sarcoplasmic Reticulum – endoplasmic reticulum.
Sarcoplasm – cytoplasm, it contains mitochondria & many nuclei.
Myofibrils, are bundles of long fibers. They are made up of thick & thin
filaments.
Homework (pgs. 263-265) March 05, 1999
?Attachments?
Most muscles span joints & are attached to bones (or other structures) in
at least two places & when a muscle contracts, the movable bone, the
muscle?s insertion, moves toward the immovable are less movable bone,
the muscles origin. In the muscles of the limbs, the origin usually lies
proximal to the insertion.
Muscle attachments, whether origin or insertion, may be direct or indirect.
In direct attachments, the epimysium of the muscle is fused to the
periosteum of a bone or perichondrium of a cartilage. In indirect
attachments, the muscle?s connective tissue wrappings extend beyond the
muscle as a rope-like tendon or a flat, broad aponeurosis. The tendon or
aponeurosis anchors the muscle to the connective tissue covering of a
skeletal element (bone or cartilage) or to the fascia of other muscles. The
temporalis muscle of the head has both direct & indirect (tendinous)
attachments.
Of the two, indirect attachments are much more common in the body
because of their durability & small size. Since tendons are mostly tough
collagenic fibers, they can cross rough bony projections which would tear
apart the more delicate muscle tissues. Because of their relatively small
size, more tendons than fleshy muscles can pass over a joint — thus,
tendons also conserve space.
Myofibrils
When viewed at high magnification, each muscle fiber is seen to contain a
large number of rod-like myofibrils that run in a parallel fashion & extend
the entire length of the cell. Each are 1-2 m in diameter, the myofibrils are
so densely packed that the mitochondria & other organelles appear to be
squeezed between then. There are hundreds to thousands of myofibrils in
a single muscle fiber, depending on its size, & they account for about 80%
of the cellular volume. The myofibrils are the contractile elements of the
skeletal muscle cells.
Striations, Sarcomeres, & Myofilaments
Striations – a repeating series of dark & light bands, are evident along the
length of each myofibril. The dark bands are called A bands because they
are anisotropic; that is, they can polarize visible light. The light bands,
called I bands, are isotropic, or non polarizing. In an intact muscle fiber,
the myofibril bands are nearly perfectly aligned with one another & this
gives the cell as a whole a stripped (striated) appearance.
Each A band has a lighter stripe in the midsection called the H zone
(bright). The H zones are visible only in relaxed muscle fibers. Each H zone
is bisected by a dark line called the M line. The I bands also have a mid-line
interruption, a darker area called the Z discs. A sarcomere is the region of
the myofibril between two successive Z discs. About 2 m long, the
sarcomere is the smallest contractile unit of a muscular fiber. Thus, the
functional units of the skeletal muscle are actually very minute
proportions of the myofibrils, & the myofibrils are chains of sarcomeres
aligned end-to-end like boxcars in a train.
If we examine the banding pattern of a myofibril at the molecular level, we
see that it arises from an orderly arrangement of two types of even
smaller structures, called filaments or myofilaments, within the
sarcomeres. The thick filaments extend the entire length of the A band.
The more lateral thin filaments extend across the I bands & part way into
the A band. The Z discs, also called a Z line, is a coined shaped protein
sheet that anchors the thin filaments & also connects each myofibril to the
next throughout the width of the muscle cell. The H zone of the A band
appears less dense when viewed microscopically because the thin
filaments do not overlap the thick ones in this region. The M line in the
center of the H zone is slightly darker because of the presence of fine
strands that hold adjacent thick filaments together in that area.
A longitudinal view of the mylofilaments is a bit misleading because it gives
the impression that each thick filament interdigitates with only four thin
filaments. In areas where thin & thick filaments overlap, each thick
filament is actually surrounded by a hexagonal arrangement of six thin
filaments.