Unit 2

Support & Movement

Fundamentals of Anatomy & Physiology

Frederic H. Martini PowerPoint ® Lecture Slides prepared by Professor Albia Dugger, Miami –Dade College, Miami, FL Professor Robert R. Speed, Ph.D., Wallace Community College, Dothan, AL Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Chapter 6: Osseous Tissue and Bone Structure

The Skeletal System  Skeletal system includes:  Bones of the skeleton  Cartilages  Ligaments  Connective tissues

What are the functions of the skeletal system?

Functions of the Skeletal System 1.

2.

3.

4.

5.

6.

Support Storage of minerals ( calcium ) Storage of lipids ( yellow marrow ) Blood cell production ( red marrow ) Protection Leverage (

force of motion

)

How are bones classified?

Classification of Bones  Bone are identified by:  shape  internal tissues  bone markings

Bone Shapes 1.

2.

3.

4.

5.

6.

Long bones Flat bones Sutural bones Irregular bones Short bones Sesamoid bones

Long Bones  Are long and thin  Are found in the:  Arms  Legs  Hands  Feet  Fingers  Toes

Long Bones

Femur

http://www.artem medicalis.com/media/jpeg/femur.jpg

Figure 6–1a

Flat Bones  Are thin with parallel surfaces  Are found in the:  Skull  Sternum  Ribs  Scapula

Flat Bones http://www.health.com/health/static/hw/med ia/medical/hw/n1249.jpg

Figure 6–1b

Sutural Bones  Are small, irregular bones  Are found

between

skull the flat bones of the

Sutural Bones

Figure 6–1c

Irregular Bones  Have complex shapes  Examples:  Spinal vertebrae  Pelvic bones http://radiology.usc.edu/Presentations/S addleProsthesis/pelvic%2520girdleb.jpg

Irregular Bones

Figure 6–1d

Short Bones  Are small and thick  Examples:  Bones found in the  Ankles (

tarsals )

 Wrists (

carpals

)

Short Bones

Tarsals

http://www.hpssandiego.com/KN043.jpg

Figure 6–1e

Sesamoid Bones  Are small and flat  Develop inside tendons near:  Joints of knees  Hands  Feet

Sesamoid Bones

Figure 6–1f

Bone Markings  Depressions or grooves:  along bone surface  Projections:  where tendons and ligaments attach  at articulations with other bones  Tunnels:  where blood and nerves enter bone

Bone Markings *

Table 6–1 (1 of 2)

Bone Markings

Table 6–1 (2 of 2)

Long Bones  The femur

Figure 6–2a

Long Bones  Diaphysis :  the shaft  Epiphysis :  wide part at each end  articulation with other bones  Metaphysis :  where diaphysis and epiphysis meet

The Diaphysis  Made up of a heavy wall of

compact bone

( dense bone )  A central space called

marrow cavity

The Epiphysis  Mostly spongy (

cancellous

) bone  Covered with compact bone (

cortex

)

Flat Bones  The parietal bone of the skull

Figure 6–2b

Flat Bones  Resembles a sandwich of spongy bone  Between 2 layers of compact bone

What are the types and functions of bone cells?

Bone ( Osseous ) Tissue  Dense, supportive connective tissue  Contains specialized cells  Produces solid matrix of calcium salt deposits around collagen fibers

Characteristics of Bone Tissue  Dense matrix , containing:  deposits of calcium salts  bone cells ( osteocytes ) within lacunae organized around blood vessels

Characteristics of Bone Tissue  Canaliculi :  form pathways for blood vessels  exchange nutrients and wastes

Characteristics of Bone Tissue  Periosteum :  covers outer surfaces of bones  consist of:  outer fibrous layer  inner cellular layer http://www.nlm.nih.gov/medlineplus/ency/ima ges/ency/fullsize/9734.jpg

Matrix Minerals  Two-thirds of the bone matrix is calcium  phosphate , Ca 3 (PO 4 ) 2 : reacts with calcium hydroxide , Ca(OH) 2 to form crystals of hydroxyapatite , Ca 10 (PO 4 ) 6 (OH) 2  which incorporates other calcium salts and ions Ca 3 (PO 4 ) 2 + Ca(OH) 2 Ca 10 (PO 4 ) 6 (OH) 2

Matrix Proteins  One-third of the bone matrix is protein fibers (

collagen

)

Bone Cells  Make up only 2% of bone mass:  osteocytes  osteoblasts  osteoprogenitor cells  osteoclasts

Osteocytes  Mature bone cells that maintain the bone matrix

Figure 6–3 (1 of 4)

Osteocytes  Live in lacunae  Are between layers ( lamellae ) of matrix  Connect by cytoplasmic extensions through canaliculi in lamellae  Do not divide

Osteocyte Functions  To maintain protein and mineral content of matrix  To help repair damaged bone

Osteoblasts  Immature bone cells that secrete matrix compounds ( osteogenesis )

Figure 6–3 (2 of 4)

Osteoid  Matrix produced by osteoblasts , but not yet calcified to form bone  Osteoblasts surrounded by bone become osteocytes

Osteoprogenitor Cells  Mesenchymal stem cells produce osteoblasts that divide to

Figure 6–3 (3 of 4)

Osteoprogenitor Cells  Are located in the inner, cellular layer of periosteum (

endosteum

)  Assist in fracture repair

Osteoclasts  Secrete acids and protein-digesting enzymes

Figure 6–3 (4 of 4)

Osteoclasts  Giant, multinucleate cells  Dissolve bone matrix and release stored minerals (

osteolysis

)  Are derived from stem cells that produce macrophages

Homeostasis  Bone building (by osteocytes) and bone recycling (by osteoclasts) must balance:  more breakdown than building, bones become weak  exercise causes osteocytes to build bone

What is the difference between compact bone and spongy bone?

Compact Bone

Figure 6–5

http://i27.photobucket.com/albums/c190/lovesthesunset/anatomy%20and%20physi ology/bonecanaliculiandHaversiancanal.jpg

Osteon  The basic unit of mature compact bone  Osteocytes are arranged in

concentric lamellae

 Around a central canal ( Haversian canal ) containing blood vessels

Perforating Canals  Perpendicular to the central canal  Carry blood vessels into bone and marrow

Circumferential Lamellae  Lamellae wrapped around the long bone  Binds osteons together

Spongy Bone

Figure 6–6

Spongy Bone  Does not have osteons  The matrix forms an open network of trabeculae  Trabeculae have no blood vessels

Red Marrow  The space between trabeculae is filled with red bone marrow :  has blood vessels  forms red blood cells  supplies nutrients to osteocytes

Yellow Marrow  In some bones, spongy bone holds yellow bone marrow :  is yellow because it stores fat

Weight–Bearing Bones  The femur transfers weight from hip joint to knee joint:  causing

tension

on the lateral side of the shaft  and

compression

on the medial side

Figure 6–7

Periosteum and Endosteum  Compact bone is covered with membrane:  periosteum on the outside  endosteum on the inside

Periosteum

Figure 6–8a

Periosteum  Covers all bones:  except parts enclosed in joint capsules  It is made up of:  an outer , fibrous layer  and an inner , cellular layer

Perforating Fibers  Collagen fibers of the periosteum:  connect with:  collagen fibers in bone  fibers of joint capsules  attached tendons  ligaments

Functions of Periosteum 1.

2.

3.

Isolate bone from surrounding tissues Provide a route for circulatory and nervous supply Participate in bone growth and repair

Endosteum

Figure 6–8b

Endosteum  An incomplete cellular layer:  lines the marrow cavity  covers trabeculae of spongy bone  lines central canals

Endosteum  Contains:  osteoblasts  osteoprogenitor cells  osteoclasts  Is active in bone growth and repair

What is the difference between intramembranous ossification and endochondral ossification?

Bone Development  Human bones grow until about age 25  Osteogenesis :  bone formation  Ossification :  the process of replacing other tissues with bone

Calcification  The process of depositing calcium salts  Occurs during bone ossification and in other tissues

Ossification  The 2 main forms of ossification are:  intramembranous ossification  endochondral ossification

Intramembranous Ossification  Also called dermal ossification :  occurs in the dermis  produces dermal bones such as the mandible and clavicle  There are 3 main steps in intramembranous ossification

Intramembranous Ossification: Step 1  Mesenchymal cells aggregate:  differentiate into osteoblasts  begin ossification at the ossification center  develop projections called spicules

Intramembranous Ossification: Step 1

Figure 6–11 (Step 1)

Intramembranous Ossification: Step 2  Blood vessels grow into the area:  to supply the osteoblasts  Spicules connect:  trapping the blood vessels inside bone

Intramembranous Ossification: Step 2

Figure 6–11 (Step 2)

Intramembranous Ossification: Step 3  Spongy bone develops and is remodeled into:  osteons of compact bone  periosteum OR  marrow cavities

Intramembranous Ossification: Step 3

Figure 6–11 (Step 3)

Endochondral Ossification  Ossifies bones that originate as hyaline cartilage  Most bones originate as hyaline cartilage

How does bone form and grow?

Endochondral Ossification  Growth and ossification of long bones occurs in 6 steps

Endochondral Ossification: Step 1  Chondrocytes in the center of hyaline cartilage:  enlarge  form struts and calcify  die, leaving cavities in cartilage

Figure 6–9 (Step 1)

Endochondral Ossification: Step 2  Blood vessels grow around the edges of the cartilage  Cells in the perichondrium change to osteoblasts:  producing a layer of superficial bone around the shaft which will continue to grow and become compact bone (

appositional growth

)

Endochondral Ossification: Step 2

Figure 6–9 (Step 2)

Endochondral Ossification: Step 3  Blood vessels enter the cartilage:  bringing fibroblasts that become osteoblasts  spongy bone develops at the primary ossification center

Figure 6–9 (Step 3)

Endochondral Ossification: Step 4  Remodeling creates a marrow cavity :  bone replaces cartilage at the metaphyses

Figure 6–9 (Step 4)

Endochondral Ossification: Step 5  Capillaries and osteoblasts enter the epiphyses:  creating secondary ossification centers

Figure 6–9 (Step 5)

Endochondral Ossification: Step 6  Epiphyses fill with spongy bone:  cartilage within the joint cavity is articulation cartilage  cartilage at the metaphysis is epiphyseal cartilage

Endochondral Ossification: Step 6 Figure 6–9 (Step 6)

Endochondral Ossification  Appositional growth :  compact bone thickens and strengthens long bone with layers of circumferential lamellae

PLAY

Endochondral Ossification

Figure 6–9 (Step 2)

What are the characteristics of adult bones?

Epiphyseal Lines

Figure 6–10

Epiphyseal Lines  When long bone stops growing after puberty:  epiphyseal cartilage disappears  is visible on X-rays as an epiphyseal line

Mature Bones  As long bone matures:  osteoclasts enlarge marrow cavity  osteons form around blood vessels in compact bone

Blood Supply of Mature Bones  3 major sets of blood vessels develop

Figure 6–12

Blood Vessels of Mature Bones  Nutrient artery and vein :  a single pair of large blood vessels  enter the diaphysis through the nutrient foramen  femur has more than 1 pair

Blood Vessels of Mature Bones  Metaphyseal vessels :  supply the epiphyseal cartilage  where bone growth occurs

Blood Vessels of Mature Bones  Periosteal vessels provide blood to:  superficial osteons  secondary ossification centers

Lymph and Nerves  The periosteum also contains:  networks of  lymphatic vessels  sensory nerves

How does the skeletal system remodel and maintain homeostasis, and what are the effects of nutrition, hormones, exercise, and aging on bone?

Remodeling  The adult skeleton:  maintains itself  replaces mineral reserves  Remodeling :  Recycles and renews bone matrix  involves osteocytes, osteoblasts, and osteoclasts

KEY CONCEPTS

 Bone continually remodels, recycles, and replaces  Turnover rate varies  If deposition is greater than removal, bones get stronger  If removal is faster than replacement, bones get weaker

Effects of Exercise on Bone  Mineral recycling allows bones to adapt to stress  Heavily stressed bones become thicker and stronger

Bone Degeneration  Bone degenerates quickly  Up to 1/3 of bone mass can be lost in a few weeks of inactivity

KEY CONCEPTS

 What you don’t use, you lose  Stresses applied to bones during physical activity are essential to maintain bone strength and mass

Effects of Hormones and Nutrition on Bone  Normal bone growth and maintenance requires nutritional and hormonal factors

Minerals  A dietary source of calcium and phosphate salts :  plus small amounts of magnesium , fluoride , iron , and manganese

Calcitriol  The hormone calcitriol :  is made in the kidneys  helps absorb calcium and phosphorus from digestive tract  synthesis requires vitamin D 3 (cholecalciferol)

Vitamins  Vitamin C is required for collagen synthesis, and stimulates osteoblast differentiation  Vitamin A stimulates osteoblast activity  Vitamins K and B 12 proteins help synthesize bone

Other Hormones  Growth hormone bone growth and thyroxine stimulate  Estrogens and androgens osteoblasts stimulate  Calcitonin and parathyroid hormone regulate calcium and phosphate levels

Hormones for Bone Growth and Maintenance

Table 6–2

The Skeleton as Calcium Reserve  Bones store calcium and other minerals  Calcium is the most abundant mineral in the body

Chemical Composition of Bone

Figure 6–13

Functions of Calcium  Calcium ions are vital to:  membranes  neurons  muscle cells (especially heart cells)

Calcium Regulation  Calcium ions in body fluids:  must be closely regulated  Homeostasis is maintained:  by calcitonin and parathyroid hormone  which control storage, absorption, and excretion

Calcitonin and Parathyroid Hormone Control  Bones:  where calcium is stored  Digestive tract:  where calcium is absorbed  Kidneys:  where calcium is excreted

Parathyroid Hormone (PTH) Figure 6–14a

Parathyroid Hormone (PTH)  Produced by parathyroid glands in neck 

Increases

calcium ion levels by:  stimulating osteoclasts  increasing intestinal absorption of calcium  decreases calcium excretion at kidneys

Calcitonin

Figure 6–14b

Calcitonin  Secreted by C cells (parafollicular cells) thyroid in 

Decreases

calcium ion levels by:  inhibiting osteoclast activity  increasing calcium excretion at kidneys

KEY CONCEPTS (1 of 2)

 Calcium and phosphate ions in blood are lost in urine  Ions

must

be replaced to maintain homeostasis  If not obtained from diet, ions are removed from the skeleton, weakening bones  Exercise and nutrition keep bones strong

What are the types of fractures, and how do they heal?

Fractures  Fractures :  cracks or breaks in bones  caused by

physical stress

 Fractures are repaired in 4 steps

Fracture Repair: Step 1

Figure 6–15 (Step 1)

Fracture Repair: Step 1  Bleeding:  produces a clot ( fracture hematoma )  establishes a fibrous network  Bone cells in the area die

Fracture Repair: Step 2

Figure 6–15 (Step 2)

Fracture Repair: Step 2  Cells of the endosteum and periosteum:  Divide and migrate into fracture zone  Calluses stabilize the break:  external callus of cartilage and bone

surrounds

break  internal callus develops in

marrow cavity

Fracture Repair: Step 3

Figure 6–15 (Step 3)

Fracture Repair: Step 3  Osteoblasts:  replace central cartilage of external callus with spongy bone

Fracture Repair: Step 4

Figure 6–15 (Step 4)

Fracture Repair: Step 4  Osteoblasts and osteocytes remodel the fracture for up to a year:  reducing bone calluses

PLAY

Steps in the Repair of a Fracture

Major Types of Fractures

Pott’s Fracture

Figure 6–16 (1 of 9)

Comminuted Fractures

Figure 6–16 (2 of 9)

Transverse Fractures

Figure 6–16 (3 of 9)

Spiral Fractures

Figure 6–16 (4 of 9)

Displaced Fractures

Figure 6–16 (5 of 9)

Colles’ Fracture

Figure 6–16 (6 of 9)

Greenstick Fracture

Figure 6–16 (7 of 9)

Epiphyseal Fractures

Figure 6–16 (8 of 9)

Compression Fractures

Figure 6–16 (9 of 9)

What are the effects of aging on the skeletal system?

Age and Bones  Bones become thinner and weaker with age  Osteopenia 40 begins between ages 30 and  Women lose 8% of bone mass per decade, while men lose 3%

Effects of Bone Loss  The epiphyses, vertebrae, and jaws are most affected, resulting in:  fragile limbs  reduction in height  tooth loss

Osteoporosis  Severe bone loss  Affects normal function  Over age 45, occurs in:  29% of women  18% of men

Hormones and Bone Loss  Estrogens and androgens help maintain bone mass  Bone loss in women accelerates after menopause

Cancer and Bone Loss  Cancerous tissues release osteoclast activating factor that:  stimulates osteoclasts  produces severe osteoporosis

SUMMARY (1 of 5)  Bone shapes, markings, and structure  The matrix of osseous tissue  Types of bone cells

SUMMARY (2 of 5)  The structures of compact bone  The structures of spongy bone  The periosteum and endosteum

SUMMARY (3 of 5)  Ossification and calcification  Intramembranous ossification  Endochondrial ossification

SUMMARY (4 of 5)  Blood and nerve supplies  Bone minerals, recycling, and remodeling  The effects of exercise

SUMMARY (5 of 5)  Hormones and nutrition  Calcium storage  Fracture repair  The effects of aging