Lect08 Skeletal NVC Bio105 Fa16 · 2017. 2. 14. · 7 Copyright © 2009 Pearson Education, Inc....

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Skeletal System

Bio 105

Copyright © 2009 Pearson Education, Inc.

Outline

I.  Overview of the skeletal system II.  Function of bones III.  Bone structure IV.  Bone cells V.  Cartilage VI. Tendons and Ligaments VII. Joints VIII. Bone development IX. Hormonal regulation of bone growth X.  Homeostasis XI. Disorders of the skeletal system


Skeletal System

§  The 4 main components of the skeletal system are different types of connective tissues: §  Bones – rigid structure § Cartilage – soft, cushions the joints §  Ligaments – attach bone to bone §  Tendons – attach muscle to bone.

§ Tendons link the skeletal and the muscular systems.

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1.  Supports and gives shape to the body. 2.  Protects soft body parts. 3.  Produces blood cells. 4.  Stores minerals (calcium and phosphate). 5.  Stores fat. 6.  Along with the muscles, permits flexible

body movement.

Functions of the Skeletal System


Bone §  Bones have different types of tissue

§ Calcified tissue = osseous tissue § Blood vessels § Nerves

§  Contain collagen fibers that give flexibility §  The combination of calcified tissue and

collagen fibers make the bone strong but flexible.


Bone Structure

§  All bones have two layers:

§ Compact Bone – Dense mineralized outer layer.

§ Spongy Bone – Inner layer with open network filled with marrow.


Periosteum

§  Periosteum – Fibrous outer covering of the bone. Contains nerves, blood vessels, and lymphatic vessels.

§  Functions in bone repair and growth.

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Typical Long Bone Structure

§  Epiphysis – Rounded end of the typical long bone, composed mainly of red marrow where blood cells are made.

§  Diaphysis – Shaft of the typical long bone, has a cavity filled with yellow marrow where fat is stored.


Typical Long Bone Structure

Figure 5.1a

Spongy bone (spaces contain

red bone marrow)

Compact bone on surface Yellow

bone marrow

Blood vessel

Periosteum

Central cavity (contains yellow bone marrow)

(a) A long bone, such as the femur of the leg, consists of a shaft and two heads, or enlarged ends. Compact bone is located on the outer surface of the bone. Spongy bone is found in the heads.


Spongy Bone

Figure 5.1e Copyright © 2009 Pearson Education, Inc.

Bone Is Living Tissue

Figure 5.1b

Blood vessels and nerve in

central canal

Spongy bone Compact bone

Osteon

Bone-forming cells (osteoblasts)

(b) The structural unit of compact bone is an osteon. Mature, living bone cells (osteocytes) are found in small spaces within the hard matrix.

Periosteum

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Compact Bone Structure

§  Osteon – structural unit of the compact bone.

Spongy bone Compact bone

Osteon


Osteon Structure

§  Central Canal (Haversian) – Contain blood vessels and nerves.

§  Osteocytes – Mature bone cells. Maintain bone structure and density.

§  Found in cavities called lacunae.

§  Canaliculi - Canals that connect the lacunae to the central canal.


The Structure of Bone


The Structure of Bone

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Bone Cells

§  Osteoblasts §  Osteocytes §  Osteoclasts


Osteoblasts

§  Osteoblasts = Bone forming cells.

§  Immature cells that secrete material called “bone ground substance” = non-cellular matrix that surrounds the cells.

§  Osteoblasts mature into osteocytes after they have secreted enough material.


Osteoclasts

§  Osteoclasts – Bone removing cells.

§  These are bone cells on the outer edge of bones.

§  They release enzymes that eat away at the compact bone, releasing minerals.


The arrow is pointing to:

Diap

hysis

Epiphysis

50%50%1.  Diaphysis 2.  Epiphysis

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The arrow is pointing to:

Diap

hysis

Epiphysis

50%50%1.  Diaphysis 2.  Epiphysis


Immature cells that secrete calcified material are:

1.  Osteoclasts 2.  Osteocytes 3.  Osteoblasts


Immature cells that secrete calcified material are:

1.  Osteoclasts 2.  Osteocytes 3.  Osteoblasts


Osteocytes are found in cavities called

Cen

tral c

anals

Colla

gen

Lacuna

e

Vellus

25% 25%25%25%1.  Central canals 2.  Collagen 3.  Lacunae 4.  Vellus

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Osteocytes are found in cavities called

Cen

tral c

anals

Colla

gen

Lacuna

e

Vellus

25% 25%25%25%1.  Central canals 2.  Collagen 3.  Lacunae 4.  Vellus


§  The skeleton begins to form at about 6 weeks.

§  Most bones only grow through adolescence but some bones continue to grow through about age 25.

§  Bones continue to change throughout life. §  Osteoclasts are removing the bone matrix. §  Osteoblasts are building the bone matrix.

§  Ossification – formation of bones.

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Bone Development and Growth


Figure 5.3 Steps of Bone Formation in Long and Short Bones

2 months

Fetal Development

Cartilage model

3 months 9 months

Bone collar Deteriorating

cartilage matrix

Calcified cartilage Blood vessel

Birth Spongy

bone formation

Childhood

Spongy bone

Compact bone

Step 2: Osteoblasts form a collar of bone around the shaft of the model.

Step 4: Secondary centers of bone formation develop in the ends of the bone.

Step 5: Cartilage remains only on the surfaces that rub against other bones and in the cartilage growth plates.

Cartilaginous surface

Step 1: A cartilaginous model of the future bone forms.

Cartilaginous (epiphyseal) growth plate

Step 3: The shaft of the cartilage model begins to hollow out, and spongy bone fills the space. Blood vessels continue to penetrate the area, and the region of bone formation expands.


Cartilage in Bones

§  Two regions of cartilage remain at each end of the long bone.

§  The cap that covers the surfaces that rub against other bones.

§  A plate of cartilage called the epiphyseal plate, or growth plate.

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Bone Growth

§  Bone growth is stimulated by growth hormone during childhood.

§  Thyroid hormones ensure that the skeleton grows with the proper proportions.

§  At puberty increasing levels of male or female sex hormones initially stimulate cartilage cells to divide. Eventually the hormones allow for the growth plates to fuse and bone can no longer increase in length.


§  Growth hormone (GH) - Directly stimulates growth of the epiphyseal plate and bone growth in general.

§  Vitamin D - Converted to a hormone (calcitrol) causing the intestines to absorb calcium.

§  Sex hormones - Adolescents experience a growth spurt due to an increased level of sex hormones.

10-7

Hormonal Regulation of Bone Growth


Hormonal Regulation of Bone Maintenance §  Parathyroid hormone (PTH) – Produced

by the parathyroid gland - accelerates bone recycling and increases blood calcium.

§  Calcitonin – Produced by the thyroid gland - a hormone that decreases blood calcium levels, deposits calcium into the bone.

§  Homeostasis – Maintaining a balance of calcium levels in blood and in bone.

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Healing Broken Bones

§  Broken bones and fractures are the same thing.

§  Bone fractures are healed by fibroblasts and osteoblasts.

§  When a break occurs, there is bleeding followed by a clot.

§  Fibroblasts secrete collagen fibers that form a callus linking the two parts of the bone. This is later replaced by bone.


Bone Fractures are Healed by Fibroblasts and Osteoblasts

Figure 5.4 (1 of 2)

Blood clot (hematoma)

Step 1: Within hours after the fracture, a blood clot forms.

Step 2: A cartilaginous callus is formed by invading fibroblasts.

Formation of blood clot

Spongy bone struts

Formation of cartilaginous callus

Cartilaginous callus


Bone Fractures are Healed by Fibroblasts and Osteoblasts

Figure 5.4 (2 of 2)

Step 3: Osteoblasts form new bone, converting the cartilaginous callus to a bony callus.

Step 4: The fracture is healed and bone is remodeled, restoring bone to original shape.

New blood

vessels

Formation of bony callus Bone remodeling

Bony callus Healed

fracture


This hormones accelerates bone recycling and increases blood calcium

Gro

wth hor

mone

Calc

itonin

Parathyro

id ho

rmon

e

33% 33%33%1.  Growth hormone 2.  Calcitonin 3.  Parathyroid hormone

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This hormones accelerates bone recycling and increases blood calcium

Gro

wth hor

mone

Calc

itonin

Parathyro

id ho

rmon

e

33% 33%33%1.  Growth hormone 2.  Calcitonin 3.  Parathyroid hormone


Calcitonin is produced by the ______ gland

Parathyro

id

Thyroid

Anter

ior pitu

itary

Hyp

othala

mus

25% 25%25%25%1.  Parathyroid 2.  Thyroid 3.  Anterior pituitary 4.  Hypothalamus


Calcitonin is produced by the ______ gland

Parathyro

id

Thyroid

Anter

ior pitu

itary

Hyp

othala

mus

25% 25%25%25%1.  Parathyroid 2.  Thyroid 3.  Anterior pituitary 4.  Hypothalamus


Cartilage

§  Cartilage - Flexible connective tissue not as strong as bone tissue.

§  Function: Cushion joints, provides flexibility.

§  Found at the ends of long bones, nose, ends of ribs, larynx and trachea, disks between vertebrae and knee, ear flaps and epiglottis.

§  Cartilage cells are chondrocytes. §  Cartilage lacks blood vessels, so slow to

heal.

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10-4 Copyright © 2009 Pearson Education, Inc.

Tendons and Ligaments §  Ligaments – Dense (white fibrous)

Connective Tissue that connects bone to bone.

§  Tendons – Dense (white fibrous) Connective Tissue that connects muscle to bone.


§  Freely movable joints held together by ligaments.

§  Synovial membrane - Produces synovial fluid, an excellent lubricant for the joints.

§  Bursae – Fluid filled sacs, reduce friction.

§  Meniscus – Cartilage between the bones, acts as a cushion.

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Synovial Joints


Synovial Joints

Figure 5.13a

A layer of cartilage on the articulating surfaces of the bones reduces friction as the bones move.

Femur

(a) Synovial joints, such as the knee shown here, permit a great range of movement.

A bursa is a fluid-filled sac that cushions certain joints and reduces friction between tendons and ligaments.

The joint cavity is filled with synovial fluid, which serves as a shock absorber and lubricant.

The synovial membrane forms the inner surface of the joint cavity and secretes synovial fluid.

Tibia

Fat pad

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Synovial Joints

Figure 5.13b

Quadriceps tendon

Femur

Fibula

Tibia

Posterior cruciate ligament

Anterior cruciate ligament

Medial collateral ligament Patellar ligament

Patella (kneecap)

(b) Ligaments hold bones together, support the joint, and direct the movement of the bones.

Lateral collateral ligament


Cartilage cells are:

fibro

cytes

osteocy

tes

chondr

ocyte

s

33% 33%33%1.  fibrocytes 2.  osteocytes 3.  chondrocytes


Cartilage cells are:

fibro

cytes

osteocy

tes

chondr

ocyte

s

33% 33%33%1.  fibrocytes 2.  osteocytes 3.  chondrocytes


This type of connective tissue connects bone to bone

Ligamen

ts

Tendon

s

50%50%1.  Ligaments 2.  Tendons

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This type of connective tissue connects bone to bone

Ligamen

ts

Tendon

s

50%50%1.  Ligaments 2.  Tendons


Fluid filled sacs are called:

Synovia

Men

isci

Bursa

e

33% 33%33%1.  Synovia 2.  Menisci 3.  Bursae


Fluid filled sacs are called:

Synovia

Men

isci

Bursa

e

33% 33%33%1.  Synovia 2.  Menisci 3.  Bursae


§  Osteoarthritis - Deterioration of cartilage at joints. §  Rheumatoid Arthritis – Chronic inflammation of

the joints due to an autoimmune disorder. §  Sprain – When ligaments are stretched or torn. §  Bursitis – Inflammation of a bursa. §  Tendonitis – Inflammation of tendon sheath. §  Fracture – Broken bone.

§  Simple = Bone breaks but does not penetrate the skin. §  Compound = Bone breaks and protrudes through the

skin.

10-22

Disorders of the Skeletal System

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Osteoporosis

§  When more bone is reabsorbed than is formed. This is when homeostasis is not maintained and more calcium is taken out of the bones than is replaced.

§  Estrogen and Testosterone help maintain the bone density.

§  After menopause women produce less estrogen and this can lead to less bone density.



Risk Factors for Osteoporosis

§  Post menopausal §  Not enough exercise §  Poor diet, not enough calcium in the diet §  Smoking §  Low vitamin D levels §  Certain hormonal disorders


Treatment for Osteoporosis

§  Exercise. §  Increased Calcium in the diet, calcium

supplements if needed, the type of calcium supplement is important.

§  Estrogen replacement therapy. §  Prescription drugs.

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Recommended Calcium Intakes*

Ages Amount mg/day Birth - 6 months 210 6 months - 1 year 270 1-3 500 4-8 800 9-13 1300 14-18 1300 19-30 1000 31-50 1000 51-70 1200 70 or older 1200


Food Calcium (mg) % DV*

Yogurt, plain, low fat, 8 oz. 415 42% Yogurt, fruit, low fat, 8 oz. 245-384 25%-38% Sardines, canned in oil, with bones, 3 oz. 324 32% Cheddar cheese, 1 ½ oz shredded 306 31% Milk, non-fat, 8 fl oz. 302 30% Tofu, firm, ½ cup 204 20% Mozzarella, part skim 1 ½ oz. 275 28% Orange juice, calcium fortified, 6 fl oz. 200-260 20-26% Turnip greens, boiled, ½ cup 99 10% Kale, cooked, 1 cup 94 9% Turnip greens, boiled, ½ cup 99 10% Ready to eat cereal, calcium fortified, 1 cup 100-1000 10%-100% Cottage cheese, 1% milk fat, 1 cup unpacked 138 14%


Decreased Calcium Absorption

§  Oxalic acid – potent inhibitor of calcium absorption, and is found in high concentrations in spinach and rhubarb and in somewhat lower concentrations in sweet potato and dried beans.

§  Sodium – Increased sodium intake results in increased loss of calcium in the urine.

§  Protein – As dietary protein intake increases, the urinary excretion of calcium also increases.

§  Caffeine – Caffeine in large amounts increases urinary calcium content for a short time.

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Fractured bones are the same thing as broken bones

True

False

50%50%1.  True 2.  False


Fractured bones are the same thing as broken bones

True

False

50%50%1.  True 2.  False


Important Concepts §  Read Ch 7

§  What are the four components of the skeletal system, and their functions

§  What are the functions of bone

§  What are the two layers of bone

§  What is the periosteum and what is its function

§  What is the structure of the osteon, what are the features found in the osteon


Important Concepts

§  What are the three types of bone cells and their functions

§  What are the functions of cartilage, tendons, and ligaments.

§  What are the parts of synovial joints and their functions

§  What are the hormones involved in bone growth and homeostasis, what glands produce calcitonin and parathyroid hormones

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Important Concepts

§  What are the disorders of the skeletal system

§  How do bones heal

§  What is osteoporosis, what are the risk factors, what can you do to prevent it.


Definitions

§  Compact bone, osteon, central canal (haversian canal), Spongy bone, Epiphysis, Diaphysis, Periosteum, lacunae, callus, fibroblasts, Osteoblasts, Osteocytes, Osteoclasts, Chondrocytes, growth hormone, Parathyroid hormone (PTH), Calcitonin, Vitamin D, epiphyseal plate, growth plate

Lect08 Skeletal NVC Bio105 Fa16 · 2017. 2. 14. · 7 Copyright © 2009 Pearson Education, Inc....

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Transcript of Lect08 Skeletal NVC Bio105 Fa16 · 2017. 2. 14. · 7 Copyright © 2009 Pearson Education, Inc....