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Chapter 4 Organization of the Body and Integumentary System 81
Figure 4-11 Second-degree burn. (From Fleisher GR,
Ludwig S, Baskin MN. Atlas of Pediatric Emergency Medicine.
Philadelphia, PA: Lippincott Williams & Wilkins; 2004.)
Figure 4-11 shows a second-degree burn.
In addition to the level or intensity of the burn, the
BSA, body surface area, of the burn is evaluated to determine the percentage of the body that has been involved.
The rule of nines is the formula used to estimate the
burned surface area. The rule of nines applies 9% of the
skin to the head; 9% for each arm, including front and
back; 18% to the front of the trunk; 18% to the back
of the trunk; 18% to each lower extremity; and 1% to
the genital area. Figure 4-12 shows the rule of nines and
percentage distribution of burns to the body.
9
When a person is burned, there is always concern
for infection. The skin is a major defense against invading microorganisms. Damaged, burned skin becomes
an avenue of entry for pathogens that cause infection.
Smoke and chemical inhalation may cause respiratory
complications. Burn patients need to be monitored carefully for wound care and pain control. Fluid replacement is also essential.
Skin Cancer
In the United States, skin cancer is the most common
form of cancer. Sun exposure is the skin’s worst enemy
especially for fair skin people who live in climates where
the sun is intense such as the Southwest. Early detection
and treatment are crucial to managing any cancer. Basal
cell and squamous cell carcinomas form in the epidermis
usually on the neck, face, and hands.
Melanoma is a malignant tumor of melanocytes. This
cancer can be anywhere in the body originating from
a mole or birthmark called a nevus. Although it may
appear as a mole, melanoma will have irregular, uneven
borders, increase in size, and change color. Figure 4-13
shows two types of melanoma, supercial and nodular.
Case Question
A
F
F
How would you respond to the patient
if she asks if she should continue going
to the pool every day?
18 back
18 front
99
18
1
18
Figure 4-12 Rule of nines. (Reprinted from Kronenberger
J, Ledbetter J. Lippincott Williams & Wilkins’ Comprehensive
Medical Assisting. 5th ed. Philadelphia, PA: Wolters Kluwer;
2016.)
18
99
1
18 back
18 front
13.513.5
Skin Infections
Skin infections can be caused from bacteria, viruses, and
fungi. The physician needs to determine the type of infection in order to properly treat each type of infection.
1 cm
A
Figure 4-13 Malignant melanoma. A. Supercial
melanoma. B. Nodular melanoma. (Reprinted from
Kronenberger J, Ledbetter J. Lippincott Williams & Wilkins’
Comprehensive Medical Assisting. 5th ed. Philadelphia,
PA: Wolters Kluwer; 2016.)
B
1 cm
82 Section II Anatomy and Physiology
Bacterial Infections
Bacterial infections can be caused by simple scratches
on the skin or deep lacerations. The pathogen causing
the infection invades the skin tissue and, if it spreads,
may lead to cellulitis, a more serious condition requiring antibiotics. Figure 4-14 shows a cellulitis infection
of the toe.
Impetigo is another type of infection caused from a
staphylococcal bacterial. It is acute and highly contagious. Blister-like lesions form lled with a watery uid
or pus. The blisters frequently form around the mouth
and nose.
Viral Infections
Herpes is a virus that affects the skin. Type I herpes,
herpes simplex virus, causes cold sores and fever blisters,
watery vesicles. The most common place for these to
form is around the mouth and nose and on the skin and
mucous membranes. Type II herpes causes genital infections. Herpes zoster is the virus that causes shingles. It is
the same virus that causes chickenpox (varicella) but is
seen in adults. The viral infection follows the nerves and
causes skin lesions along the course of the nerve. The
most common place for shingles to form is on the trunk
of the body around or near the waist. This infection is
very painful and the affected area is highly sensitive to
touch. There is a singles vaccine available now that is
recommended for adults. See Figure 4-15.
Another viral skin infection is caused by the human
papillomavirus, HPV, group. This virus causes warts.
These small tumors can appear anywhere on the body
Figure 4-15 Shingles. (Reprinted from Kronenberger J,
Ledbetter J. Lippincott Williams & Wilkins’ Comprehensive
Medical Assisting. 5th ed. Philadelphia, PA: Wolters
Kluwer; 2016.)
but are commonly found on the soles of feet (plantar
wart) and on the hands. Genital warts are usually benign
but may be associated with cancer of the cervix.
Fungal Infections
Mycotic (fungal) infections, commonly known as tinea,
may appear on the face, body, scalp, hands, or feet.
Tinea corporis is knows as ringworm because of the red,
ring-shaped lesions it forms. It has nothing to do with
worms. See Figure 4-16.
Figure 4-14 Cellulitis infection. (Reprinted from
Kronenberger J, Ledbetter J. Lippincott Williams & Wilkins’
Comprehensive Medical Assisting. 5th ed. Philadelphia,
PA: Wolters Kluwer; 2016.)
Figure 4-16 Ringworm. (Reprinted from Kronenberger J,
Ledbetter J. Lippincott Williams & Wilkins’ Comprehensive
Medical Assisting. 5th ed. Philadelphia, PA: Wolters
Kluwer; 2016.)
Chapter 4 Organization of the Body and Integumentary System 83
Athlete’s foot is a fungal growth on the feet promoted
by dampness and perspiration. Fungal infections can be
caused from wearing acrylic nails. The moisture forms
under the nail and the fungus has an ideal environment
for growth. Antifungal agents are available in topical
and oral preparations.
Inammatory Skin Disorders
Dermatitis refers to any inammation of the skin and
may be acute or chronic. The cause of the inammation may not be realized and the skin may clear on its
own. Chronic inammation may be more serious and
problematic.
Figure 4-18 Psoriasis. (Reprinted from Kronenberger J,
Ledbetter J. Lippincott Williams & Wilkins’ Comprehensive
Medical Assisting. 5th ed. Philadelphia, PA: Wolters
Kluwer; 2016.)
Acute Inammatory Disorders
Urticaria, or hives, is caused from an allergic reaction.
The allergen may be a known substance such as certain foods or medications, or it might be in response
to a toxin such as venom or contact with animal dander. Hypersensitivity to these agents causes elevated red
patches called wheals. Eczema is a skin inammation
that causes intense itching. The affected area appears red
with blisters or pimple-like lesions. Scaling and crusting
of the skin also is present. Eczema may be the result
from contact with irritants such as poison ivy, detergents, and other chemicals. See Figure 4-17.
With the intense itching, the affected person will
want to scratch the skin, which may lead to a secondary bacterial infection due to the broken skin. Patients
with inammatory skin disorders benet from the
effects of corticosteroids or antihistamines to reduce the
inammation.
Chronic Inammatory Disorders
Systemic lupus erythematosus, SLE, is a chronic inammatory disease, which is an autoimmune disease of connective tissue. An autoimmune disease results from an
immune reaction to one’s own tissues. SLE may affect
Figure 4-17 Eczema. (Reprinted from Kronenberger J,
Ledbetter J. Lippincott Williams & Wilkins’ Comprehensive
Medical Assisting. 5th ed. Philadelphia, PA: Wolters
Kluwer; 2016.)
the skin and other body organs. On the skin, there
may be light purple papules on the face and scalp. One
specic sign associated with this disease is a butteryshaped rash that appears on the nose and cheeks. SLE
lesions are worsened by exposure to sunlight. This disease is more common in women than men. Scleroderma
is another autoimmune disease with unknown cause.
There is an overproduction of collagen causing thickening and tightening of the skin. Severe scleroderma
causes hardening of the skin making movements impossible especially on the face, around the mouth, and the
forearms.
Psoriasis is caused from an overgrowth of kerati-
nocytes in the epidermis. Large areas of red at areas
appear covered with silvery scales. Psoriasis is treated
with topical corticosteroids and exposure to ultraviolet
light. See Figure 4-18.
Accessory Organ Disorders
Acne is a common disorder caused by oversecretion of
oil from the sebaceous glands. Acne vulgaris is a form
of acne typically found in people between the ages of
14 and 25 years. The hormones that control sebaceous
secretions become particularly active during this time
period. Acne is characterized by the formation of blackheads and pimples. Excessive oil, sebum, combines with
keratinocytes and form a plug within the hair follicle.
The plug darkens resulting in a blackhead. When the
oil forms a plug within the hair follicle and becomes
blocked, it bulges, forming a whitehead, or pimple.
Antibiotics, topical and oral, may be used to treat acne.
Alopecia is baldness and most commonly occurs in
men as a condition known as male pattern baldness. It
usually is linked to heredity and aging. Baldness may
also be caused by systemic conditions such as uncontrolled diabetes and thyroid disease. Topical medications are somewhat effective in producing hair growth.
Chemotherapeutic drugs, used in treating cancer, are
also linked to baldness, but when the drugs are discontinued, the hair growth resumes.
84 Section II Anatomy and Physiology
C
O
G
WOUND HEALING
AND CARE
When the skin is damaged or injured, repair of the damage starts to take place. After the area heals, a scar, called
a
cicatrix, may remain on the skin’s surface. A scar is
formed from connective tissue and is strong when healed
but is not as exible as the surrounding tissue. When a
wound is sutured together, the scarring is minimized since
there is not as much connective tissue needed for repair.
Wound Care
The medical assistant will provide wound care for
patients who present with new injuries and for those who
need follow up care. For initial care, water or saline solution is used to cleanse the wound. It is important to wear
disposable gloves when providing wound care. The physician will examine the wound and decide if sutures are
indicated for the wound. The key to healing any wound
is infection control. Antibacterial ointments may be used
if needed. Sterile dressings are the most effective way to
protect the wound from infection. Patients should be
instructed to keep the wound dry and clean. The medical
assistant may need to demonstrate to the patient how to
change the dressing without contaminating the wound.
may delay the healing process due to poor circulation
of some patients.
Prevent infection—when a wound is contaminated,
r
the healing process is prolonged due to inammation
of the tissues. Infection also interferes with the formation of materials needed to heal the wound.
Age—as we age, the healing process also slows due
r
to the slower replacement of cells. Older persons may
also have a lowered immune response to infection
causing the healing to take longer.
C
O
G
DERMATOLOGY
Dermatology is the study of the skin and a dermatologist
is a physician specialist who treats patients with various
conditions of the skin and accessory organs. Diagnostic
procedures, performed by the physician, include the initial physical examination of the skin. The medical assistant will be asked to assist in the collection of wound
cultures and bandaging wounds. Dermatologists rely
on a skin biopsy to exam lesions for malignant growth.
Medical assistant need to provide patient education to
ensure compliance with wound care.
The Healing Process
The goal with wound care is to promote proper and efcient healing of the wound. There are factors that may
affect the healing process.
Proper nutrition—patients should maintain a bal-
r
anced diet with the nutrients needed for cell repair
and regrowth. Vitamins and minerals are important
especially vitamins A and C needed for the production of collagen.
Rich blood supply—blood supplies tissues with oxy-
r
gen and nutrients and carries away the waste products that could increase during the healing process.
White blood cells are necessary to attack the bacteria
at the site of the wound. Diseases such as diabetes
Preparing for Externship
It is never too early to start thinking about your
externship course and preparing as much as you
can ahead of time. One of the things that most sites
require is an interview so they can initially meet the
student and determine if it will be a good t to have
this person in their facility. Think of the interview
as if you were actually applying for a job with the
facility. There may be an open position that the stu-
Cultural Connection
Working in any medical practice, the medical assistant may observe patients with marks or bruises on
their skin. Although some of these may be caused
from trauma, falls, and abuse, there are other reasons for specic discolorations of the skin. Among
the Asian culture, specically Chinese, there is a
practice called cupping. It is a method or treatment
that involves creating a vacuum, or suction, by heating and applying hot glass cups to the body. Circular
areas of bruising are left on the skin once the cups
are removed. This strange practice is thought to
help blood disorders, skin problems (eczema and
acne), as well as other health conditions.
dent could ll after completion of the externship. The
externship site uses the weeks of externship with
the student as a working interview. They want to see
how the person interacts with the staff and patients
as well as how well the student completes assigned
duties. Start thinking about the questions the site
may ask and develop a few questions that you will
ask during the interview.
Chapter 4 Organization of the Body and Integumentary System 85
Chapter Recap
● The study of anatomy and physiology is the basic
starting place for anyone entering the health care
eld. It is critical that we have an understanding of
the main structures and functions of the body.
● The abdomen is divided with imaginary lines into
nine regions and four quadrants. These divisions
allow for more accurate descriptions of the location
of body organs and patient’s pain or discomfort.
● The body requires maintenance of homeostasis in
order to remain healthy. Negative feedback is required
in most situations to bring the body back into balance.
● The integumentary system is one of eleven systems
in the body. The other systems include the skeletal,
Online Resources for Students
Resources for students available on thepoint.
lww.com include the following:
● Audio Glossary
● Animations
muscular, nervous, endocrine, cardiovascular,
lymphatic, respiratory, digestive, urinary, and
reproductive systems.
● The skin is the body’s major rst line of defense
against invading microorganisms and protects
underlying structures. The skin is also key is helping
to maintain body temperature.
● There are many skin conditions and diseases,
which may result from bacteria, fungi, viruses, and
parasites.
● The most dangerous skin cancer is melanoma. All
persons need to avoid the sun’s UV rays, which
contribute to the development of skin cancer.
● Competency Evaluation Forms
● Harris CareTracker Case Studies
● Interactive Games & Activities
● Certication Preparation Question Bank
● Videos
Exercises and Activities
Certication Preparation Questions
1. Chronic skin disease characterized by red at
areas covered with silvery scales.
a. Urticaria
b. Eczema
c. Shingles
d. Psoriasis
2. The dermis is
a. supercial
b. deep
c. lateral
d. medial
3. What type of gland is involved in acne?
a. Sudoriferous
b. Sebaceous
c. Ceruminous
d. Endocrine
to the epidermis.
4. Which of the following is not a type of skin
lesion?
a. Pallor
b. Vesicle
c. Papule
d. Laceration
5. Which skin discoloration is caused by an
accumulation of bile pigment in the blood?
a. Pallor
b. Cyanosis
c. Jaundice
d. Carotenemia
6. If a person received burns over both lower
extremities and the genital area, what percentage
of the body is burned?
a. 18%
b. 19%
c. 27%
d. 37%
86 Section II Anatomy and Physiology
7. Which science studies normal body structure?
a. Homeostasis
b. Anatomy
c. Physiology
d. Pathology
8. Where is intracellular uid located?
a. Between body cells
b. In blood plasma
c. In lymph
d. Inside body cells
9. A plane that divides the body into right and left
portions is a:
a. frontal plane.
b. transverse plane.
c. sagittal plane.
d. horizontal plane.
10. Which cavity contains the mediastinum?
a. Abdominal
b. Dorsal
c. Thoracic
d. Pelvic
Skeletal and Muscular
5
Systems
Chapter Objectives
● Describe the structure and growth of long bones.
● Identify the major bones of the axial skeleton.
● Identify the major bones of the appendicular
skeleton.
● Describe various types of bone disorders and
fractures.
● Recognize normal and abnormal curves of the spine.
● Identify the categories of joints and the movement
provided by each one.
● Compare the three types of muscle tissue.
● Explain the function of skeletal muscle.
● Name some of the major muscles of the body and
describe their location and function.
● Compare isotonic and isometric contractions.
● Describe major muscle disorders.
● Describe diagnostic and treatment methods
associated with musculoskeletal disorders.
● Discuss the role of the medical assistant in the
orthopedic ofce.
CAAHEP & ABHES Competencies
CAAHEP
● Describe the structural organization of the human
body.
● Identify body systems.
● List the major organs in each body system.
● Describe the normal function of each body system.
● Identify common pathology related to each body
system including signs, symptoms, and etiology.
● Analyze pathology for each body system including
diagnostic measures and treatment modalities.
Chapter Terms
Abduction
Adduction
Appendicular
Arthrocentesis
ABHES
● List all body systems and their structure and
functions.
● Describe common diseases, symptoms, and
etiologies as they apply to each system.
● Identify diagnostic and treatment modalities as they
relate to each body system.
Arthroplasty
Arthroscopy
Articular cartilage
Atrophy
87
88 Section II Anatomy and Physiology
Axial
Cancellous
Chondrosarcoma
Circumduction
Collagen
Cramps
Diaphysis
Dislocation
Dorsiexion
Endosteum
Epiphyseal plates
Eversion
Abbreviations
ATP
DIP
Case Study
Extension
Flexion
Fontanelles
Hyperextension
Hypertrophy
Insertion
Inversion
Isometric
Isotonic
Ligaments
Medullary cavity
Origin
DJD
MP
Osseous tissue
Ossicles
Ossication
Osteitis deformans
Osteoblast
Osteoclast
Osteocyte
Osteogenesis imperfecta
Osteomalacia
Osteomyelitis
Osteoporosis
Osteosarcoma
OA
PIP
Periosteum
Plantar exion
Pronation
Rickets
Rotation
Sesamoid bone
Spasm
Sprain
Strain
Supination
Tendons
RA
Hunter, a 7-year-old second grader, was playing on
the monkey bars at school and fell to the ground landing on his wrist. He immediately felt pain in his lower
arm and wrist. When he went to the school nurse,
she put an ice pack on his arm and called his mother
to come pick him up from school. His mother immediately took Hunter to their primary care physician to
have his arm examined. The doctor ordered an x-ray
This chapter presents both the skeletal and muscular systems, which work together allowing the body to move,
provide support, and protect vital internal organs. In
order for the body to move, the bones and muscles need
joints to allow bending.
C
O
G
The human body uses the skeleton as a framework, so
the bones must be strong to support and protect the
body and the internal structures. The skeletal bones
have several functions in the body, some of which may
not seem so apparent at rst. The bones:
r
r
r
THE SKELETAL SYSTEM
Provide a framework for the body
Protect underlying structures such as the brain, spinal
cord, heart, and lungs
Work with the muscles to produce movement
of his lower arm, wrist, and hand. The x-ray revealed
that Hunter had a greenstick fracture of the radius. A
short arm cast was applied, and his arm was put into a
sling. The doctor requested a follow-up appointment
in 2 weeks. The medical assistant provided Hunter’s
mother with an instruction sheet that included information on cast care and signs or symptoms to watch
for that might require immediate medical care.
Store calcium salts, which may be released into the
r
blood when calcium is needed
Produce blood cells in the red marrow
r
There are approximately 206 bones in the human skeleton. The skeleton is subdivided into the axial skeleton,
which includes the bones of the head and torso, and the
appendicular skeleton, which includes all the bones of the
extremities. The word appendicular means pertaining to
the appendages. Figure 5-1 shows the axial and appendicular divisions of the skeleton as well as the major bones.
Case Question
A
F
F
medical assistant, how would you respond to him?
Hunter is very upset that he will not be
able to play on the monkey bars or play
softball for a few weeks. If you are the
Chapter 5 Skeletal and Muscular Systems 89
Cranium
Facial bones
Mandible
Sternum
Vertebral
column
Ilium
(of pelvis)
Pelvis
Sacrum
Clavicle
Scapula
Humerus
Ulna
Metacarpals
Phalanges
Femur
Patella
Ribs
Radius
Carpals
Proximal
epiphysis
Diaphysis
Cartilage
yseal line
Epiph
(growth line)
Spongy bone
(containing
red marrow)
Endosteum
Compact bone
Medullary
(marrow) cavity
Artery and vein
Yellow marrow
Periosteum
Calcaneus
Metatarsals
Figure 5-1 Axial and appendicular skeleton. (Reprinted
from Cohen BJ. Memmler’s The Human Body in Health
and Disease. 13th ed. Philadelphia, PA: Wolters Kluwer;
2014.)
Fibula
Tibia
Tarsals
Phalanges
The skeletal bones are classied by their shape. There
are
Flat bones—examples include ribs and cranium
r
Irregular bones—examples include vertebrae and
r
facial bones
Short bones—examples include carpals (wrist) and
r
tarsals (ankle)
Long bones—examples include arms and legs
r
Parts of the Bone
Long bones are elongate in shape and have a narrow
shaft called the diaphysis. Through the center of the
diaphysis is the
row is located. The irregularly shaped end of the long
medullary cavity where the bone mar-
Distal
epiph
ysis
Figure 5-2 Bone diagram. (Reprinted from Cohen BJ.
Memmler’s The Human Body in Health and Disease.
13th ed. Philadelphia, PA: Wolters Kluwer; 2014.)
bone is called the epiphysis. There is a proximal end and
a distal end of the bone. The proximal end is closer to
the midpart of the body and the distal end farther away.
For example, the femur’s (thigh bone) proximal end is
at the hip and the distal end is at the knee. Figure 5-2 is
a cutaway diagram of a bone showing the various parts
and layers.
Bone Tissue
The bones are made up of living tissue, osseous tissue,
and have their own blood vessels and nerves. The bone’s
strength and hardness is due to the matrix between the
bone cells. The bones also require
substance, which allows the bones to bend slightly and
not break or shatter. There are three types of cells within
bone tissue:
Osteoblasts—the cells responsible for building bone
r
tissue
Osteocytes—mature bone cells
r
Osteoclasts—the cells responsible for resorption, the
r
breakdown of bone tissue
collagen, a protein
90 Section II Anatomy and Physiology
Types of Bone Tissue
There are two types of bone tissue, compact and spongy.
Compact bone is hard, dense tissue that makes up the
main shaft of long bones. Spongy bone, also known as
cancellous bone, is found at the ends of the long bones,
the epiphyses (pl), and in the lining of the medullary cavity. The bones are covered by a membrane called perios-
teum
, except at the joint regions. The endosteum lines
the bone marrow cavity. Blood vessels within the periosteum help to maintain the bone throughout life. Nerve
bers are also located in this membrane and provide sensations such as pain when there is injury or damage to
the bone. Osteoblasts are found in both membranes and
are necessary to build, repair, and maintain the bone.
Bone Marrow
There are two kinds of bone marrow, red and yellow.
Red marrow is found in the spongy bone at the ends
of long bones and at the center of other bones. Blood
cells are manufactured in the red marrow. The yellow
marrow is primarily made up of fat. During the early
periods of development, the long bones of babies and
children contain more red marrow to maintain the
increased need for new blood cells.
Bone Formation and Regulation
calcium supply. Vitamin D, acquired through the diet,
is necessary to promote calcium absorption from the
intestine. As we age, the bones may lose density due to
the slowing of bone tissue renewal. The bones become
weaker, and it takes longer to heal injuries.
Bone Markings
Why do bones have various shapes? They need the
nooks, depressions, holes, and curves to allow the other
structures of the body to attach and allow nerves and
blood vessels to pass through. Some major bone markings include the following:
Projection—outgrowth or protuberance on a bone
r
Process—large projection of a bone
r
Head—round end of the bone with a slender region
r
below it, the neck (head of the femur)
Condyle—round projection (epicondyle is a small
r
projection above a condyle)
Crest—ridge or border (iliac crest of the hip)
r
Spine—sharp projection (spine of the shoulder blade)
r
Foramen—hole or opening that allows a blood vessel
r
or nerve to pass through
Sinus—cavity or hollow space (sinuses of the face)
r
Fossa—depression on bone surface
r
Meatus—passageway or channel (auditory meatus,
r
ear canal)
During fetal development, the bones are composed
primarily of cartilage. As the fetus develops, cartilage
converts to bone during the process of
Ossication takes place when the osteoclasts remove the
cartilage and the osteoblasts deposit new bone tissue.
Once the material has hardened, the cells, osteocytes,
continue to maintain the bone matrix. The transformation of cartilage into bone begins at the center of the
shaft of the bone and continues to develop toward the
ends of the bone. At birth, the ends of long bones have
epiphyseal plates where continued growth of the bone
takes place. When a person reaches approximately
20 years of age, the bones stop growing. After the growing stops, the epiphyseal plate becomes a thin line known
as the epiphyseal line. Doctors can evaluate the age of an
individual based on the presence of the epiphyseal plate
or line shown on x-rays.
Throughout a person’s life, the bones are maintained and repaired through a process called resorption.
Osteoblasts build up new bone matrix, and osteoclasts
clean up the bone tissue by resorbing it. This process is
essential when there is a fracture of a bone. The bone
will heal and return to the proper shape through the
process of resorption.
Formation and resorption relies on the parathyroid
hormone produced by the parathyroid glands (posterior
to the thyroid gland). This hormone regulates osteoclast
activity. The bones also store the majority of the body’s
ossication.
The Axial Skeleton
The axial skeleton includes the 80 bones of the head and
trunk. The word axial refers to the axis or situated on
the axis of a structure of the body.
Bones of the Head
The head, referred to as the skull, divides into two parts,
the cranium and the facial bones.
Cranium
The cranium is a rounded structure that covers the
brain. There are eight individual cranial bones.
Frontal—forms the forehead, the front of the skull’s
r
rook, and the top of the eye orbits
Parietal—two bones that form most of the top and
r
the side walls of the cranium
Temporal—two bones that form the sides and the
r
base of the skull
Ethmoid—fragile bone located between the eyes; the
r
downward extension of this bone forms much of the
nasal septum
Sphenoid—at the base of the skull in front of the tem-
r
poral bones and forms part of the eye orbit
Occipital—forms the posterior portion of the skull;
r
the foramen magnum (large hole) is located at the
base of the occipital bone and allows passage of the
spinal cord from the brain