Gross and Microscopic Anatomy of the Bone Study Guide

Question 1

During development, the human skeleton is initially made of………?

Answer 1

Skeletal cartilage

Question 2

Define the perichondrium.

Answer 2

Dense irregular tissue connective tissue that surrounds the cartilage

Question 3

List the 3 types of cartilage. What are the distinguishing features of each type? Be ready to provide an example of each type.

Answer 3

• Hyaline
  
  • Most abundant type
  • Provides support, flexibility, resilience
  • Contains spherical chondrocytes + collagen fibers
  • Ex. articular (joint) surfaces, larynx, trachea, nose
• Elastic
  
  • Similar to hyaline but contains more elastic fibers
  • Ex. external ear, epiglottis
• Fibrocartilage
  
  • Contains thick collagen fibers
  • Highly compressible, great tensile strength
  • Ex. menisci of knee, intervertebral discs

Question 4

What are the basic components of cartilage?

Answer 4

Chondrocytes and extracellular matrix

Question 5

What are the 2 ways that cartilage can grow?

Answer 5

• Appositional growth: chondrocytes in the perichondrium secrete matrix against the external face of existing cartilage
• Interstitial growth: chondrocytes within lacunae divide and secrete new matrix - cartilage grows from within

Question 5

What type of cell is responsible for cartilage’s growth?

Answer 5

Chondrocytes (cartilage forming cells)

Question 6

List and define the functions of bone.

Answer 6

• Support: for body and soft organs
• Protection: protect brain, spinal cord, and vital organs
• Movement: provide levers for muscle action
• Mineral + growth factor storage: calcium + phosphorus + growth factor are stored/released as needed
• Hematopoiesis: (blood cell formation) occurs within red bone marrow
• Triglyceride/fat storage: yellow marrow in some bone cavities
• Hormone production: osteocalcin is secreted by bones to help regulate glucose levels/insulin secretion

Question 7

Generally, what bones belong to the axial skeleton? To the appendicular?

Answer 7

• Axial: skull, vertebrae, rib cage
• Appendicular: extremities and girdle

Question 8

Define the following categories: long, short, flat, and irregular bones. Be ready to give examples of each type.

Answer 8

• Long bones: bones that are longer than they are wide, shaft + 2 ends (humerus, tibia, fibula, femur, radius, ulna, etc.)
• Short bones: cube-shaped bones, length grossly = width (carpals, tarsals). Includes sesamoid bones (patella)
• Sesamoid bones: a type of short bone formed within tendons in response to high compressive pressures(patella)
• flat bones; thin, flat, often slightly curved (sternum, scapulae, ribs, skull bones)
• irregular bones; complicated shapes (vetebrae, coxal bones, sphenoid, etc)

Question 9

From a functional movement perspective, what is the significance of having spongy bone?

Answer 9

Holds bone marrow, allows for flexibility when stress is placed on the bone

Question 10

What is the function of the periosteum? How is it secured to the bone matrix?

Answer 10

White, double layered membrane, covers all external surfaces except for joint surfaces, acts as anchoring point for tendons/;ligaments, secured to bone matrix by perforating fibers (in the fibrous layer)

Question 11

What is formed in the osteogenic layer of the periosteum?

Answer 11

Inner layer abutting bone, contains osteogenic stem cells that give rise to most bone cells

Question 11

How do nutrient arteries supply a bone? What type of arteries supply the ends of the long bone?

Answer 11

Nutrient arteries and veins run through a hole in the wall of the diaphysis, the nutrient foramen. Epiphyseal arteris and veins similarly supply the epiphysis

Question 12

What does red bone marrow do? Yellow marrow? Where can we find it in children? Adults?

Answer 12

• Red marrow: hematopoietic (blood forming) tissue. (most active areas are diploe of flat and irregular bones)
  
  • In newborns: medullary cavities and all spongy bone
  • In adults: exists in heads of femur and humerus, the flat bones, and the irregular bones
• Yellow marrow: fat storage, replaces most areas of red marrow overtime

Question 13

Why do we have bone markings? What causes them? What type of person might have less defined or non-existent bone markings?

Answer 13

• Why: sites of muscle, ligament, and tendon attachment on the external surfaces of the bones, Sites involved in joint formation, conduits for blood vessels and nerves
• Cause: mechanical stress
• Person w less: bed ridden people who are not weight bearing on their bones, infants; people who are not walking yet, astronauts;people who are in an antigravity environment with minimal stress on the bones/weight bearing

Question 13

Can the type of bone marrow change over time, yes or no? If yes, how/when?

Answer 13

• Yellow converts to red in times of severe anemia
• Red turns to yellow as we grow

Question 14

Be familiar with the 3 major types of bone markings and how they are formed.

Answer 14

• Projection: outward bulge of bone; may result from increased stress from muscle pull or as a modification for joints
• Depression: bowl or groove-like cut out; can serve as a passageway for vessels or nerves; plays a role in joints
• Opening: hole or canal in bone; severs as passageway for blood vessels or nerves

Question 15

Familiarize yourself with the following subclasses of bone markings: tuberosity, trochanter, tubercule, epicondyle, spine, head, condyle, fissure, foramen, fossa, meatus, and sinus. You should already know them from the lab

Answer 15

• meatus; canal like passageway (ear)
• trochanter; large, blunt, irregular shaped process (rim looking bulges on femur)
• fissure; narrow slit-like opening (slit looking openings in the eyes)
• foramen; oval/round opening in the bone (in the skull - foramen spinosum)
• fossa; shallow basin-like depression, often serving as an articular surface (radial and coronoid fossae on the humerus where it articulates the radius and ulna)
• sinus; cavity within a bone, filled with air and lined with mucous membrane (bones behind the nose)
• tuberosity; large rounded projection (greater and lesser tuberosity by the head of the humerus)
• tubercle; small rounded projection or process (adductor tubercle on femur)
• condyle; rounded articular projection, often articulates with a corresponding fossa ( medial and lateral condyles on the femur)
• epicondyle; raised area on/above an epicondyle (medial and lateral epicondyles on femur)
• spine; sharp, slender often pointed projection (iliac spine)
• head; bony expansion carried on a narrow neck (head of femur)

Question 16

What are the 5 types of bone cells? What does each type do? How do osteoblasts become osteocytes?

Answer 16

• Osteoprogenitor cells: mitotically active stem cells in the periosteum and endosteum, can differentiate into osteoblasts when stimulated, others will remain osteogenic cells
• Osteoblasts: mitotically active bone-forming cells; secrete osteoid, become osteocytes when surrounded by the matrix being secreted
• Osteocytes: spider like in appearance, mature bone cells in lacunae; no longer actively dividing, maintain bone matrix; act as stress/strain sensors, respond to mechanical stimuli + changing calcium levels by communicating to osteoblasts/osteoclasts
• Bone-lining cells: flat cells on bone surfaces, believed to help maintain matrix (with osteocytes), called periosteal cells on the external bone surface and endosteal cells on the internal bone surface
• Osteoclasts: giant multinucleated cells that function in bone resorption (breakdown) they’re located in depressions called resorption bays, have ruffed edges to increase surface area, and when active,
• osteoblasts become osteocytes when they become surrounded by the matrix being secreted

Question 17

What other type of cell is functionally and anatomically similar to an osteoclast?

Answer 17

Macrophages

Question 17

Be prepared to label the parts of an osteon – lamellae, central(haversian) canal, perforating (volkmann’s)canals, lacunae, canaliculi, interstitial lamellae, and circumferential lamellae.

Question 18

Define osteoid. What is it made of?

Answer 18

• Unmineralized bone matrix secreted by osteoblasts
• Made of collagen and calcium-binding proteins

Question 19

What is the significance of the alternating directions of the collagen fibers in the lamellae?

Answer 19

To resist tension

Question 20

What lies between the collagen fibers in the lamellae?

Answer 20

Calcium phosphate crystals; makes the bone hard and able to withstand compression

Question 21

How are canaliculi formed? What is their functional importance?

Answer 21

• Formation: osteocytes (trapped osteoblasts) maintain their connections with eachother as bone hardens. A network of tiny canals containing the osteocyte extensions is created. Canaliculi tie all the osteocytes in a mature osteon together and allow communication + passage of nutrition / waste
• Function: hair like canals that connect lacunae to each other and to the central canal

Question 22

What are the inorganic components of bone?

Answer 22

• Hydroxyapatites (mineral salts)
  
  • Make up 65% of bone by mass
  • Mainly tiny calcium phosphate crystals
  • Present to create hardness and resist compression
• Last long after human death

Question 23

The organic components of bone resist —- and —— while the inorganic components of bone provide ——- and resist ———-.

Answer 23

• tension
• stretch
• hardness
• compression