NOTES ON ANATOMY

The Skeletal System

Chapter Summary

The skeletal system is one of the body systems that students enjoy studying most. Naming the bones is, at first, a challenge, then rapidly becomes a source of confidence as students develop their identification skills. Learning about the dynamic nature of bones also dispels many preconceived ideas that students may have about bones resembling dead twigs or remaining unchanged over time.

This chapter begins with an overview of the many functions of bones, including their role in support, protection, and movement of the body, as well as in the storage of nutrients and in blood cell formation. Next, bones are classified as long, short, flat, or irregular, each made up of either spongy or compact bone, or a combination of both to meet unique body needs. The macroscopic (gross) anatomy of a long bone provides a conceptual image of bone structure, and the microscopic anatomy helps students to begin to understand the complexity of bone and the reasons for its dynamic nature. The principles of bone ossification, growth, and remodeling are explored, along with the role of calcium and vitamin D in keeping bones strong and healthy. The various types of bone fractures and their resultant medical corrections are also presented to round out the students’ understanding of some common bone disorders.

In the final sections of Chapter 5, the 206 named bones that make up the axial and appendicular skeletons are presented, and their major projections and depressions are identified. The differences observed in the fetal skeleton, along with other developments throughout the life span are introduced, are examined and explained. A discussion of articulations found in the body follows the bone identification section, and the types of joints and their related inflammatory disorders.

Suggested Lecture Outline

  I. BONES: AN OVERVIEW (pp. 134–144)

     A. Functions of the Bones (pp. 134–135)

        1. Support

        2. Protection

        3. Movement

        4. Storage of Nutrients

        5. Blood Cell Formation

     B. Classification of Bones (p. 135)

        1. Composition

        2. Classification According to Shape

        a. Long Bones

        b. Short Bones

        c. Flat Bones

        d. Irregular Bones

     C. Structure of a Long Bone (pp. 135–140)

        1. Gross Anatomy

        2. Microscopic Anatomy

     D. Bone Formation, Growth, and Remodeling (pp. 140–142)

     E. Bone Fractures (pp. 142–144)

        1. Types of Fractures

        2. Treatment of Fractures

        3. Repair of Fractures

II.  AXIAL SKELETON (pp. 144–158)

     A. Skull (pp. 145–150)

        1. Cranium

        a. Frontal Bone

        b. Parietal Bones

        c. Temporal Bones

        d. Occipital Bone

        e. Sphenoid Bone

        f. Ethmoid Bone

        2. Facial Bones

        a. Maxillae

        b. Palatine Bones

        c. Zygomatic Bones

        d. Lacrimal Bones

        e. Nasal Bones

        f. Vomer Bone

        g. Inferior Conchae

        h. Mandible

        3. The Hyoid Bone

        4. Fetal Skull

     B. Vertebral Column (Spine) (pp. 150–157)

        1. Vertebral Characteristics

        2. Cervical Vertebrae

        3. Thoracic Vertebrae

        4. Lumbar Vertebrae

        5. Sacrum

        6. Coccyx

     C. Thoracic Cage (pp. 157–158)

        1. Sternum

        a. Manubrium

        b. Body

        c. Xiphoid Process

        2. Ribs

        a. True Ribs

        b. False Ribs

        c. Floating Ribs

III. APPENDICULAR SKELETON (pp. 158–166)

     A. Bones of the Shoulder Girdle (pp. 158–160)

        1. Clavicle (Collarbones)

        2. Scapulae (Shoulder Blades)

     B. Bones of the Upper Limbs (pp. 160–162)

        1. Arm

        a. Humerus

        2. Forearm

        a. Radius

        b. Ulna

        3. Hand

        a. Carpals

        b. Metacarpals

        c. Phalanges

     C. Bones of the Pelvic Girdle (pp. 162–164)

        1. Coxal (Hip) Bones

        a. Ilium

        b. Ischium

        c. Pubis

     D. Bones of the Lower Limbs (pp. 164–166)

        1. Thigh

        a. Femur

        2. Leg

        a. Tibia

        b. Fibula

        3. Foot

        a. Tarsal Bones

              i. Talus and Calcaneus

        b. Metatarsals

        c. Phalanges

IV. JOINTS (pp. 166–174)

     A. Functional Categories of Joints (pp. 166–168)

        1. Synarthroses

        2. Amphiarthroses

        3. Diarthroses

     B. Structural Categories of Joints (pp. 168–172)

        1. Fibrous Joints

        2. Cartilaginous Joints

        3. Synovial Joints

        4. Types of Synovial Joints Based on Shape

        a. Plane Joint

        b. Hinge Joint

        c. Pivot Joint

        d. Condyloid Joint

        e. Saddle Joint

        f. Ball-and-Socket Joint

     C. Homeostatic Imbalances of Joints (pp. 172–174)

        1. Bursitis

        2. Osteoarthritis (OA)

        3. Rheumatoid Arthritis (RA)

        4. Gouty Arthritis

V. DEVELOPMENTAL ASPECTS OF THE SKELETON (pp. 174–176)

     A. Fetal Development

     B. Infant and Child Development

     C. Adolescent Development

D.   Osteoporosis—Chronic Bone-Thinning Disease from Hormone Deficiency or Inactivity in Elderly

Key Terms

acetabulum

acromioclavicular joint

acromion

alae

alvelolar margin

amphiarthroses

anatomical neck

anterior border

anterior superior iliac spine

appendicular skeleton

articular cartilage

articulations (joints)

atlas

axis

axial skeleton

ball-and-socket joint

body

bone markings

bone remodeling

bony callus

bony thorax

bursae

calcaneus

canaliculi

capitulum

carotid canal

carpal bones

carpus

cartilaginous joints

central (Haversian) canals

cervical vertebrae

clavical

compact bone

condyloid joint

coracoid process

coronoid fossa

coronoid process

coronal suture

coxal bones

cranium

cribriform plates

cristagalli curvatures

diaphysis

diarthroses

deltoid tuberosity

dens

epiphyseal line

epiphyseal plate

epiphysis

external auditory meatus

facial bones

false pelvis

false ribs

femur

fibrocartilage callus

fibrous articular capsule

fibrous joints

fibula

fissures

flat bones

floating ribs

fontanels

foramen magnum

foramen ovale

glenoid cavity

greater/lesser trochanters

greater sciatic notch

gluteal tunerosity

Haversian system (osteon)

hematoma

hinge joint

humerus

hyoid bone

iliac crest

ilium

inlet

intercondylar fossa

internal acoustic meatus

interosseous membrane

interotrochanteric line

intertubercular sulcus

intervertebral discs

irregular bones

ischial spine

ischial tuberosity

ischium

joints

joint cavity

jugular foramen

jugular notch

lacunae

lamboid suture

lamellae

lateral epicondyles

lateral malleolus

lateral/medial condyles

long bones

lumbar vertebrae

manubrium (body and xiphoid) process

mastoid process

maxillary bones

medial/lateral condyles

medial malleolus

median sacral crest

medullary cavity (yellow marrow)

metacarpals

metatarsals

nasal conchae

obturator foramen

occipital condyles

olecranon fossa

olecranon process

optic canal ossification

ossa coxae

osteoblasts

osteoclasts

osteocytes

osteoporosis

outlet

palatine processes

paranasal sinuses

patellar surface

pectoral (shoulder) girdle

pelvic girdle

perforating (Sharpey’s) fibers

perforating (Volkmann’s) canals

periosteum

phalanges

pivot joint

plane joint

posterior superior iliac spine

primary curvatures

pubic bone

pubic symphysis

radial groove

radial tuberosity

radioulnar joints

radius

red marrow

reinforcing ligaments

ribs

sacral canal

sacral hiatus

sacroiliac joint

sacrum

saddle joints

sagittal suture

scapulae

secondary curvatures

sellaturcica

short bones

sinuses

skeletal system

skull

sphenoid sinuses

spongy bone

squamous sutures

sternal angle

sternum

styloid process

superior orbital fissure

suprasoapular notch

surgical neck

sutures

synarthroses

syndesmoses

synovial joints

talus

tarsal bones

tarsus

tendon sheath

tibia

tibial tuberosity

thoracic cage

thoracic vertebrae

trochlea

trochlear notch

true ribs

true pelvis

transverse processes

ulna

vertebrae

vertebral arch

vertebral column

vertebral foramen

xiphisternal joint

zygomatic process

Lecture Hints

1. Students are fascinated by the differences between male and female skeletons. Have two articulated skeletons, one of each gender, available to point out the differences as they are presented in lecture, and discuss the information that skeletons provide in forensic medicine, such as how the hyoid bone can provide evidence as to homicide or suicide upon autopsy.

    Key point: There are significant differences not only between the skeletons of males and females, but also between athletes and sedentary people, young and old people, etc., and discussing some of these differences will help students to conceptualize the dynamic nature of bones.

2. Emphasize the dynamic and ready-healing nature of bones and the fact that bones are highly vascular, with this rich blood supply accounting for why “if you are going to break something, break a bone.” Also point out that bone material is constantly being produced and reabsorbed for the purpose of calcium balance, and to accommodate functional and gravitational stress. Explain that moderate weight-bearing exercise will stimulate bone supercompensation and may delay the development of chronic diseases such as osteoporosis. Discuss the consequences of little or no weight bearing, such as with people who are wheelchair-dependent or bed-ridden.

    Key point: The dynamic nature of bones cannot be overemphasized. In this chapter, students learn valuable information about the long-term health of bones and what they can do to delay or prevent osteoporosis, arthritis, and other homeostatic imbalances.

3. Students are surprised to hear that ossification is incomplete at birth. Share a timetable of ossification with students and point out that babies crawl and walk at the time that is physiologically right for them, in part based on bone development. Also discuss greenstick fractures and their occurrence in young people whose bones are still developing.

    Key point: Ossification and bone growth and development are processes that continue into early adulthood.

4. Use a flexible, articulated skeleton to demonstrate the location of bones and their markings as you discuss them in lecture.

    Key point: It is important for students to actually see the location of the bones and touch either real bones or plastic models as they hear about each of them individually.

5. Use a skull that has been sectioned transversely to demonstrate the location of the interior bones of the skull as you discuss them during lecture.

    Key point: The interior bones of the skull are the most difficult to identify and this helps students to visualize their locations within the skull.

6. Identify the risk factors for chronic conditions such as osteoporosis and arthritis, and discuss preventative measures, current treatments, and future therapies for these conditions.

    Key point: Osteoporosis and arthritis are major health concerns in our aging population and this discussion gives students a frame of reference for understanding the causes and treatments for this condition.

7. Identify the placement and functions of the fontanels in fetal and infant skull development. Explain that fontanel means “little fountain” and is related to the fact that a baby’s pulse is palpable at these “soft spots.” This allows the skull to compress slightly during birth and the brain to grow during late pregnancy and early infancy. Note: This is why fontanels are so important. It also can provide a health indicator since a depressed fontanel could indicate dehydration while a raised fontanel could indicate increased cranial pressure.

    Key point: Students may be familiar with the location of at least the anterior fontanel and may be interested to learn of the others.

8. Spend time discussing the Haversian system. Students may find this topic confusing, but it is an important concept for them to understand since it directly relates to the dynamic nature of bones, particularly during growth and healing.

    Key point: Haversian systems, with their interlinked canals and transportation systems, provide living bone cells with the nutrients necessary for growth and healing following overuse or trauma, as well as a means of removing toxic metabolic wastes so as to keep bones healthy.

9. Discuss the various joint disorders that students are familiar with, as well as their causes and treatments.

    Key point: Joints hold bones together and provide mobility. They are the site of numerous disorders due to overuse and, at times, abuse, and it is valuable for students to appreciate their fragility as well as their complexity.

10. Discuss ruptured intervertebral disks and explain the pathology behind this disorder.

    Key point: This is often the first time that students have actually seen the vertebral column and the way it is designed to protect the spinal column. Discussing what happens when a disk “leaks” into surrounding tissues helps students to understand the severity of the disorder.

11. Emphasize the differences between osteoclasts (bone destroyers) and osteoblasts (bone formers), and explain why a dynamic balance between them is necessary.

    Key point: As new bone is formed, which is a constant process, old bone is destroyed. This represents homeostatic balance using negative feedback loops at their finest.

12. Discuss cleft palate and the surgical correction of this condition.

    Key point: Even though the maxilla appears to be one bone, it is really two bones fused at the midline. Any disruption in the fusion during fetal life results in a cleft, which severely impedes an infant’s ability to suck in critical nutrition.

13. Explain the root words of the various bones as they are presented (e.g., the manubrium of the sternum means “handle of a sword”; scapula means “spade”).

    Key point: Building upon the students’ vocabulary by providing definitions of word parts helps them to learn the names of all 206 bones more easily and will make muscles easier to locate and describe in Chapter 6.

14. The number of vertebrae within each region of the vertebral column denotes where each region begins and ends. Explain to students that while a normal human has seven cervical vertebrae, he or she will have eight cervical nerves. This is important to remember when the spinal nerves are discussed in Chapter 7.

    Key point: Vertebrae are singular and the spinal nerves are in pairs. Also, the first cervical nerve branches are superior to the first cervical vertebrae.

15. Discuss the impact of bone structure for muscle attachment.

    Key point: By understanding the role of bone shape in muscle attachment (and therefore, body movement), students can be better prepared for the muscular system in Chapter 6.

Short Answer Essay

13. Forms the body’s internal structural framework (provides support). Anchors skeletal muscles and allows them to exert force to produce movement. Protects by enclosing (skull, thorax, and pelvis). Provides a storage depot for calcium and fats. Site of blood cell formation. (pp. 134–135)

14. Yellow marrow: Substance composed of fat found in the medullary cavity of long bones in adults. (p. 136) Spongy bone looks cancellous, whereas compact bone appears to be solid, smooth, and dense. (p. 135)

15. Bone is highly vascularized and thus heals rapidly. Cartilage has poor vascularization and depends on diffusion for its nutrient supply; thus, it heals slowly or poorly, if at all. (pp. 139–140)

16. PTH plays a significant role in calcium homeostasis. When blood calcium levels begin to drop, PTH activates the osteoclasts of bone. As the bone matrix is broken down, ionic calcium is released to the blood. Mechanical forces acting on bones determine where calcium can safely be removed or where more calcium salts should be deposited to maintain bone strength. In areas where there are bulky muscles, bone needs to be thicker and form large projections for muscle attachment. (pp. 140–142)

17. Compression and comminuted fractures are particularly common in the elderly. Greenstick fractures (incomplete fractures) are more common in children because their bone matrix contains relatively more collagen and is more pliable. (p. 142; Table 5.2)

18. Two each: Temporal and parietal bones. One each: Occipital, frontal, sphenoid, and ethmoid bones. (pp. 145–147)

19. Joint between the mandible and temporal bone (temporomandibular joint). (p. 149)

10. Chin: Mandible. Cheekbone: Zygomatic. Upper jaw: Maxilla. Eyebrow ridges: Frontal. (pp. 145, 149)

21. The fetal skull has (a) much larger cranium-to-skull size ratio, (b) foreshortened facial bones, and (c) fontanelle or unfused (membraneous) areas. (pp. 149–150)

22. Cervical: 7 vertebrae; thoracic: 12 vertebrae; lumbar: 5 vertebrae. (pp. 150–151)

23. See Figure 5.14 (p. 151) and Figure 5.16 (p. 154).

24. To cushion the vertebrae and absorb shocks. Also, they allow movement and flexibility of the spinal column (e.g., laterally). A slipped disc (or herniated disc) occurs when an intervertebral disc bulges outward (protrudes) or ruptures, putting pressure on the spinal cord and/or spinal nerves. As a result, a person may feel numbness and excruciating pain in the affected area. (p. 151)

25. Sternum, ribs (attached to the vertebral column posteriorly). (p. 157)

26. A floating rib is a false rib. Floating ribs are easily broken because they have no anterior (sternal) attachment (direct or indirect) and thus have no anterior reinforcement. (pp. 157–158)

27. Clavicle and scapula. (pp. 158–160)

28. Humerus, radius, carpals. (pp. 160–161; Figure 5.6)

29. Ilium, ischium, pubis. The ilium is the largest. The ischium has the “sit-down” tuberosities. The pubis is most anterior. (pp. 162–164)

30. Femur, patella, fibula/tibia, tarsals, metatarsals, phalanges. (pp. 164–166; Figure 5.6)

31. Synarthrotic: Essentially immovable, generally fibrous. Amphiarthrotic: Slightly movable, generally cartilaginous. Diarthrotic: Freely movable, synovial. (pp. 166, 168–170; Table 5.3)

32. The articulating ends of bones in a synovial joint are covered with articular cartilage and are separated by a cavity that contains synovial fluid. Synovial joints are enclosed by a fibrous connective tissue capsule lined with a smooth synovial membrane. Reinforcing ligaments may reinforce the fibrous capsule, and bursae and tendon sheaths may cushion tendons where they contact bone. (p. 170; Figure 5.29)

33. Professor Rogers is incorrect. The foramen magnum allows nerves connecting the brain and spinal cord to pass through, whereas the esophagus allows food to pass from the mouth to the stomach. (p. 145)

34. Diaphysis. (p. 139; Figure 5.3)

35. Factors that keep bones healthy: physical stress/use (most important), proper diet (e.g., calcium). Factors that cause bones to become soft or atrophy: Disuse, hormone imbalances, loss of gravitational and movement stress. (pp. 175–176)

Answers to Critical Thinking and Clinical Application Questions

36. The youngster had more organic material in her bones, allowing them to bend, while her grandmother’s bones are completely calcified, having little organic material, and also probably thin due to osteoporosis. (pp. 140–142)

37. No; the palatine bones are posterior to the palatine processes of the maxillae. If the palatine processes do not fuse, then the palatine bones remain unfused as well. (p. 149)

38. Most likely the paranasal sinuses on the right side of the face. (p. 149; Figure 5.10)

39. Most likely osteoporosis, a condition common in older women. A decline in bone mass, particularly in the spine and neck of the femur, increases the probability of fractures. (p. 175)

40. Dislocation. The head of the humerus has been forced out of its normal position in the glenoid cavity. (p. 170)

41. This might be a spiral fracture. (p. 142; Table 5.2)

42. The epiphyseal line seen in fully grown adult bone is the remnant of the epiphyseal plate found in young, growing bone. (pp. 140, 174; Figure 5.4)

43. The joint between the temporal bone and the mandible (temporomandibular joint). (p. 149)

44. The thoracic region of the vertebral column would show abnormal curvature in scoliosis. (p. 154)


Anatomy mcq on musculockeletal system

1? Where is the weakest point in the clavicle?
a. the middle point of clavicle
b. the lateral ends
c. point where middle 2/3rd meets lateral 1/3rd’
d. point where lateral 1/4th meets middle 3/4th
e. None


2. which of the following muscles are not attached to coracoid process?
a. Short head of biceps
b. longhead of biceps
c. corachobrachialis
d. pectoralis minor
e. none

3. which muscles origins from above the glenoid fossa?
a. short head of biceps
b. long head of biceps
c. corachobrachialis
d. long head of triceps
e. deltoid

4. which of the following muscles are not inserted on greater tubercle of humerus?
a. supraspinatus
b. infraspinatus
c. teres major
d. teres minor

5. which of he following muscle inserted in lesser tubercle?
a. Supraspinatus
b. infraspinatus
c. suscapularis
d. deltoid
e. corachobrachialis

6. which of the following muscles not inserted into intertubercular groove?
a. Lattissimus dorsi
b. pectoralis major
c. teres major
d. deltoid

7. Which of the following is NOT true regarding the clavicle?
(A) Its medial end is enlarged where it attaches to the sternum.
(B) Its lateral end is ?at where it articulates with the humerus.
(C) The medial two-thirds of the shaft are convex anteriorly.
(D) The clavicle transmits shock from the upper limb to the axial skeleton.
(E) The clavicle is a “long bone” that has no medullary cavity.

8 The trapezius attaches to which of the following regions of the clavicle?
(A) lateral one-third of the clavicle
(B) conoid tubercle
(C) subclavian groove
(D) trapezoid line
(E) quadrangular tubercle

9. Which of the following is true in respect to the scapula?
(A) The spine of the scapula continues laterally as the coracoid process.
(B) The lateral surface of the scapula forms the glenoid cavity.
(C) The acromion is superior to the glenoid cavity and projects anterolaterally.
(D) The scapula is fastened securely to the thoracic cage at the scapulothoracic joint.
(E) The acromioclavicular