UNIT II: FRAMEWORK OF THE BODY

skin

made of multiple layers of cells and tissues, which are held to underlying structures by connective tissue.

epidermis

made of closely packed epithelial cells

dermis

made of dense, irregular connective tissue that houses blood vessels, hair follicles, sweat glands, and other structures.

hypodermis

lies beneath the dermis, composed mainly of loose connective and fatty tissues.

The epidermis

composed of keratinized, stratified squamous epithelium. It is made of four or five layers of epithelial cells, depending on its location in the body. It does not have any blood vessels within it.

stratum basale

the deepest epidermal layer and attaches the epidermis to the basal lamina, below which lie the layers of the dermis. The cells in the stratum basale bond to the dermis via intertwining collagen fibers, referred to as the basement membrane. A finger-like projection, or fold, known as the dermal papilla (plural = dermal papillae) is found in the superficial portion of the dermis.

Layers of the Epidermis

composed of five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

stratum spinosum

spiny in appearance due to the protruding cell processes that join the cells via a structure called a desmosome. The desmosomes interlock with each other and strengthen the bond between the cells. It is interesting to note that the “spiny” nature of this layer is an artifact of the staining process. Unstained epidermis samples do not exhibit this characteristic appearance.

stratum granulosum

has a grainy appearance due to further changes to the keratinocytes as they are pushed from the stratum spinosum. The cells (three to five layers deep) become flatter, their cell membranes thicken, and they generate large amounts of the proteins keratin, which is fibrous, and keratohyalin, which accumulates as lamellar granules within the cells.

stratum lucidum

a smooth, seemingly translucent layer of the epidermis located just above the stratum granulosum and below the stratum corneum. This thin layer of cells is found only in the thick skin of the palms, soles, and digits. The keratinocytes that compose the stratum lucidum are dead and flattened.

stratum corneum

the most superficial layer of the epidermis and is the layer exposed to the outside environment.

dermis

might be considered the “core” of the integumentary system; It contains blood and lymph vessels, nerves, and other structures, such as hair follicles and sweat glands. The dermis is made of two layers of connective tissue that compose an interconnected mesh of elastin and collagenous fibers, produced by fibroblasts.

layers of the dermis

the papillary layer and the reticular layer. Both are made of connective tissue with fibers of collagen extending from one to the other, making the border between the two somewhat indistinct.

papillary layer

made of loose, areolar connective tissue, which means the collagen and elastin fibers of this layer form a loose mesh. This superficial layer of the dermis projects into the stratum basale of the epidermis to form finger-like dermal papillae.

reticular layer

Underlying the papillary layer is the much thicker reticular layer, composed of dense, irregular connective tissue. This layer is well vascularized and has a rich sensory and sympathetic nerve supply. Appears reticulated (net-like) due to a tight meshwork of fibers. Elastin fibers provide some elasticity to the skin, enabling movement. Collagen fibers provide structure and tensile strength, with strands of collagen extending into both the papillary layer and the hypodermis. In addition, collagen binds water to keep the skin hydrated.

hypodermis

(also called the subcutaneous layer or superficial fascia) is a layer directly below the dermis and serves to connect the skin to the underlying fascia (fibrous tissue) of the bones and muscles. It is not strictly a part of the skin, although the border between the hypodermis and dermis can be difficult to distinguish. It consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the integument.

pigmentation

The color of skin is influenced by a number of pigments, including melanin, carotene, and hemoglobin. Recall that melanin is produced by cells called melanocytes, which are found scattered throughout the stratum basale of the epidermis.

melanosom

The melanin is transferred into the keratinocytes via a cellular vesicle called a

skin pigmentation

The relative coloration of the skin depends of the amount of melanin produced by melanocytes in the stratum basale and taken up by keratinocytes.

Stage 1: Stop the bleeding (hemostasis)

When you get a cut, scratch, or other wound in your skin, it usually starts bleeding. The first stage of wound healing is to stop the bleeding.

Stage 2: Scabbing over (clotting)

Once your wound isn’t bleeding any more, the body can begin cleaning and healing it.

platelets

are the clotting cells in blood, clump together to make a “plug” in the wound.

fibrin

Clotting or coagulation includes a protein called ______. It’s “blood glue” that makes a net to hold the platelet plug in place.

Stage 3: Rebuilding (growth and proliferative)

Once the wound is clean and stable, your body can begin rebuilding the site. Oxygenrich red blood cells come to the site to create new tissue. It’s like a construction site, except your body makes its own building materials.

Stage 4: Maturation (strengthening)

Even after your wound looks closed and repaired, it’s still healing. It might look pink and stretched or puckered. You may feel itching or tightness over the area. Your body continues to repair and strengthen the area.

the human skeletal system

consists of all of the bones, cartilage, tendons, and ligaments in the body.

20

the skeleton makes up about __ percent of a person’s body weight.

206

An adult’s skeleton contains ___ bones.

pelvis

The male skeleton is usually longer and has a high bone mass. The female skeleton, on the other hand, has a broader ______ to accommodate for pregnancy and child birth.

the axial skeleton and the appendicular skeleton.

the skeletal system can be broken down into two parts, known as

80

The adult axial skeleton consists of __ bones.

adult axial skeleton

It’s made up of the bones that form the vertical axis of the body, such as the bones of the head, neck, chest, and spine

skull bones

The adult skull comprises 22 bones.

cranial bones

The eight _______ _____ form the bulk of your skull. They help to protect your brain.

facial bones

There are 14 ______ _____. They’re found on the front of the skull and make up the face.

auditory ossicles

The ________ ________ are six small bones found within the inner ear canal in the skull. There are three auditory ossicles on each side of the head, known as the:

• malleus (hammer)

• incus (anvil)

• stapes (stirrup)

• They work together to transmit sound waves from the surrounding environment to the structures of the inner ear.

hyoid

a U-shaped bone found at the base of the jaw. It serves as a point of attachment for muscles and ligaments in the neck.

vertebral column

The _________ ______ is made up 26 bones. The first 24 are all vertebrae, followed by the sacrum and coccyx (tailbone).

cervical vertebrae

These seven bones are found in the head and neck.

thoracic vertebrae

These 12 bones are found in the upper back.

lumbar vertebrae

These five bones are found in the lower back.

Thoracic Cage

made up of the sternum (breastbone) and 12 pairs of ribs. These bones form a protective cage around the organs of the upper torso, including the heart and lungs.

126 bones

There are a total of ___ _____ in the appendicular skeleton.

appendicular skeleton

It consists of the bones that make up the arms and legs, as well as the bones that attach them to the axial skeleton.

pectoral girdle

is where the arms attach to the axial skeleton. It’s made up of the clavicle (collarbone) and scapula (shoulder blade).

30

Each arm contains __ bones.

The humerus

is the long bone of the upper arm.

The radius

is one of the two long bones of the forearm, found on the thumb side.

The ulna

is the second long bone of the forearm, found on the pinky finger side.

The carpals

are a group of eight bones found in the wrist area.

The metacarpals

are five bones found in the middle area of the hand.

The phalanges are

14 bones that make up the fingers.

pelvic girdle

commonly known as the hips, is where the legs attach to the axial skeleton. It’s made up of two hipbones — one for each leg.

The ilium

is the top portion of each hip bone.

The ischium

is a curved bone that makes up the base of each hip bone.

The pubis

is located in the front part of the hip bone.

30

each leg is composed of __ bones.

The femur

is the large bone of the upper leg.

The tibia

is the main bone of the lower leg. It forms the shin

The fibula

is the second bone in the lower leg, found in the outer leg.

The patella

is also called the kneecap.

The tarsals

are the seven bones that make up the ankle.

The metatarsals

are the five bones that make up the middle area of the foot.

The phalanges

are 14 bones that comprise the toes.

Fracture

• can also be referred to as a broken bone.

• typically occur due to an injury or trauma, such as a car accident or a fall.

Metabolic Bone Diseases

• refer to a group of conditions that affect bone strength or integrity.

• They can be due to things such as a deficiency in vitamin D, loss of bone mass, and use of certain medications, such as steroids or chemotherapy.

Arthritis

• an inflammation of the joints. This can cause pain and a limited range of movement.

• Several things can cause _________, including the breakdown of cartilage that’s found in joints, autoimmune conditions, or infection

Cancer

• can develop in the tissues of the bone or in the cells produced by bones. ______ that forms in the primary bone tissue is actually quite rare.

• ______s of the blood cells produced by bone, such as myeloma or lymphoma, are more common.

Spinal Curvatures

• is when the spine doesn’t curve in its usual shape. Typically, the spine follows gentle forward and backward curves.

Kyphosis

creates a rounding in the upper back.

Lordosis

causes the lower back to curve inward.

Scoliosis

causes an S- or C-shaped curve in the spine.

a joint (articulation).

The junction of two or more bones is called

synarthrosis, amphiarthro-sis, diarthrosis joints

the three basic kinds of joints:

Synarthrosis joints

are immovable, as exemplified by the skull sutures.

Amphiarthrosis joints

• such as the vertebral joints and the symphysis pubis, allow limited mo-tion.

• Its bones are joined by the fibrous cartilage.

Diarthrosis joints

are freely movable joints.

Ball-and socket joints

best exemplified by the hip and the shoulder, permit full freedom of movement.

Hinge joints

permit bending in one direction only and are best exemplified by the elbow and the knee.

Saddle joints

allow movement in two planes at right angles to each other. The joint at the base of the thumb is a sad-dle, biaxial joint.

Pivot joints

are characterized by the articulation between the radius and the ulna. They permit rotation for such activities as turning a doorknob.

Gliding joints

allow for limited movement in all directions and are represented by the joints of the carpal bones in the wrist.

joint capsule

A tough, fibrous sheath called the _____ _______ surrounds the articulating bones.

hyaline cartilage

The ends of the articulating bones of a typical movable joint are covered with smooth _______ _________.

synovium

The capsule is lined with a membrane, the ________, which secretes the lubricating and shock-absorbing synovial fluid into the joint capsule. Therefore, the bone surfaces are not in direct contact.

articular cartilage

In some synovial joints (eg, the knee), fibrocartilage disks (eg, medial meniscus) are located between the _________ _________ surfaces. These disks provide shock absorption.

Ligaments (fibrous connective tissue bands)

bind the articulating bones together.

muscle tendons

Ligaments and ______ _______, which pass over the joint, provide joint stability.

interosseous

In some joints, ____________ ligaments (eg, the cruciate ligaments of the knee) are found within the capsule and add stability to the joint.

A bursa

is a sac filled with synovial fluid that cushions the movement of tendons, ligaments, and bones at a point of friction.

the elbow, shoulder, knee, and some other joint.

Bur-sae can found at

The muscular system

a set of tissues in the body with the ability to change shape.

Muscle cells

connect together and eventually to elements of the skeletal system.

myosin filaments

The muscular system relies on the coordinated action of millions of actin and ______ _________ pulling in the same direction at the same time.

Nerve signals

originating in the brain travel to specific muscles, allowing organisms to stimulate specific muscle tissues to produce coordinated actions like running, swimming, and flying.

movement

The most obvious function of the muscular system is ________.

circulation

The second and less obvious function of the muscular system is to assist with ___________.

Visceral

________ and cardiac muscle tissues surround the blood vessels and lymph vessels that carry crucial nutrients and oxygen to the cells of the body.

Cardiac muscle

_______ ______ makes up the heart and supplies the main force for blood traveling through the body.

Large arteries, veins

_____ ________ and _____ have associated muscles which can contract or relax to control blood pressure.