Outline. Skeletal System. Functions of Bone. Bio 105: Skeletal System 3/17/2016. The material from this lecture packet will be on the lecture exam

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1 Bio 105: Skeletal System Lecture 8 Chapter 5 The material from this lecture packet will be on the lecture exam The identification that you do after this lecture will be on the lab exam Outline I. Overview of the skeletal system II. Function of s III. Bone structure IV. Bone cells V. Cartilage VI. Tendons and Ligaments VII.Joints VIII.Bone development IX. Hormonal regulation of growth X. Homeostasis XI. Disorders of the skeletal system Skeletal System Composed of different types of connective tissue Bones Cartilage Ligaments Tendons Functions of Bone Supports and gives shape to the body Protects soft body parts Produce blood cells Stores minerals Stores fat Permits flexible body movement Along with the muscles 1

2 Bone Different types of tissue Calcified tissue = Osseous tissue Blood vessels Nerves Collagen fibers 2 types Compact Spongy Bone Structure Epiphysis Bone Structure Rounded end of typical long Mainly red marrow Diaphysis Shaft of the typical long Has a cavity filled with yellow marrow Periosteum Bone Structure Fibrous outer covering of the Contains Nerves Blood vessels Lymphatic vessels Functions in repair and growth Typical Long Bone Structure Spongy (spaces contain red marrow) Compact on surface Yellow marrow Blood vessel Periosteum Spongy Bone Central cavity (contains yellow marrow) (a) A long, such as the femur of the leg, consists of a shaft and two heads, or enlarged ends. Compact is located on the outer surface of the. Spongy is found in the heads. Figure 5.1a Figure 5.1e 2

3 Bone Is Living Tissue Blood vessels and nerve in central canal Osteon Periosteum Osteon Compact Bone Structure Structural unit of compact 3 parts Central canal Osteocytes Canaliculi Bone-forming cells (osteoblasts) Spongy Compact (b) The structural unit of compact is an osteon. Mature, living cells (osteocytes) are found in small spaces within the hard matrix. Figure 5.1b Osteon Structure Central (Haversian) Canal Contain blood vessels and nerves Osteocytes Mature cells Maintain structure, density and minerals Found in cavities called lacunae Canaliculi Canals that connect the lacunae to the central canal Figure 5.1c The structure of Figure 5.1d The structure of Bone Cells Osteoblasts B for building Osteocytes Osteoclasts C for chaos 3

4 Osteoblasts Bone forming cells Immature cells Secrete material called ground substance Mature into osteocytes Osteoblasts Bone absorbing cells On the outer edge of s Release enzymes that eat away at the Releasing minerals Review Questions The arrow is point to. What immature cells secrete calcified material? What cavities are osteocytes found in? Cartilage in Bones Two regions of cartilage at each end of long s Cap Epiphyseal plate (Growth plate) Bone Development & Growth Begins to form in the fetus at about 6 weeks Grow through adolescence Some grow through about age 25 Continue to change throughout life Ossification - Formation of s Figure 5.3 Steps of formation in long and short s, from an embryo into childhood 2 months Step 1: A cartilaginous model of the future forms. Cartilage model Bone collar Fetal Development 3 months Deteriorating cartilage matrix Step 2: Osteoblasts form a collar of around the shaft of the model. 9 months Spongy formation Calcified cartilage Blood vessel Step 3: The shaft of the cartilage model begins to hollow out, and spongy fills the space. Blood vessels continue to penetrate the area, and the region of formation expands. Birth Step 4: Secondary centers of formation develop in the ends of the. Cartilaginous surface Cartilaginous (epiphyseal) growth plate Childhood Step 5: Cartilage remains only on the surfaces that rub against other s and in the cartilage growth plates. Spongy Compact 4

5 Hormonal Regulation of Bone Growth Growth Hormone (GH) Directly stimulates growth of the epiphyseal plate and growth during childhood Vitamin D Converted to a hormone Causes intestines to absorb calcium Hormonal Regulation of Bone Growth Thyroid Hormones Ensure skeleton grows with the proper proportions Sex Hormones Adolescents growth spurt secondary to increased level of hormones Allow for the closing of the growth plate as well Hormonal Regulation of Bone Calcium Levels Parathyroid Hormone (PTH) Parathyroid gland Accelerates recycling and increases blood Ca ++ Calcitonin Thyroid Gland Decreased blood Ca ++ levels Deposits Ca ++ into the Homeostasis Healing Broken Bones Broken s = Fractures Healed by fibroblasts and osteoblasts 4 steps Blood clot Callus formation Osteoblast activity Remodeling Bone Fractures are Healed by Fibroblasts and Osteoblasts Formation of blood clot Step 1: Within hours after the fracture, a blood clot forms. Cartilaginous callus Blood clot (hematoma) Formation of cartilaginous callus Step 2: A cartilaginous callus is formed by invading fibroblasts. Spongy struts Figure 5.4 (1 of 2) 5

6 Bone Fractures are Healed by Fibroblasts and Osteoblasts Formation of bony callus Bone remodeling New blood vessels Bony Healed callus fracture Fracture Healing ENmMX09c Step 3: Osteoblasts form new, converting the cartilaginous callus to a bony callus. Step 4: The fracture is healed and is remodeled, restoring to original shape. Figure 5.4 (2 of 2) Review Questions What hormone accelerates recycling and increased blood calcium? Calcitonin is produced by what gland? Cartilage Flexible connective tissue Not as strong as tissue Function Cushion joints, flexibility Cells Chondrocytes Lacks blood vessels Tendons & Ligaments Tendons vs Ligaments Image From:

7 Synovial Joints Freely movable joints Held together by ligaments 4 parts Synovial membrane Bursae Menisci Cartilage Femur Synovial Joints A bursa is a fluid-filled sac that cushions certain joints and reduces friction between tendons and ligaments. A layer of cartilage on the articulating surfaces of the s reduces friction as the s move. The joint cavity is filled with synovial fluid, which serves as a shock absorber and lubricant. Fat pad The synovial membrane forms the inner surface of the joint cavity and secretes synovial fluid. Tibia (a) Synovial joints, such as the knee shown here, permit a great range of movement. Figure 5.13a Synovial Joints Femur Quadriceps tendon Lateral collateral ligament Fibula Tibia Posterior cruciate ligament Anterior cruciate ligament Medial collateral ligament Patellar ligament Patella (kneecap) (b) Ligaments hold s together, support the joint, and direct the movement of the s. Figure 5.13b Review Questions What are cartilage cells called? What type of connective tissue connects to? What are the fluid filled sacs called? Disorders of the Skeletal System Osteoarthritis Rheumatoid Arthritis Sprains Bursitis Tendonitis Fracture Simple vs Compound 7

8 Osteoporosis More is reabsorbed than is formed More calcium is taken out of the s than is replaced Estrogen and Testosterone Help maintain density After menopause women produce less estrogen Risk Factors Osteoporosis Post menopausal Not enough exercise Poor diet Smoking Low Vitamin D levels Certain hormonal disorders Treatment Osteoporosis Exercise Increase calcium in the diet Estrogen replacement therapy Prescription drugs Recommended Calcium Intakes* Ages Amount mg/day Birth - 6 months months - 1 year or older 1200 Food Calcium (mg) % DV* Yogurt, plain, low fat, 8 oz % Yogurt, fruit, low fat, 8 oz %-38% Sardines, canned in oil, with s, 3 oz % Cheddar cheese, 1 ½ oz shredded % Milk, non-fat, 8 fl oz % Tofu, firm, ½ cup % Mozzarella, part skim 1 ½ oz % Orange juice, calcium fortified, 6 fl oz % 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% Cottage cheese, 1% milk fat, 1 cup unpacked % Decreased Calcium Absorption Oxalic acid Potent inhibitor of Ca absorption High concentrations in spinach and rhubarb Lower concentractions in sweet potato and dried beans Sodium Protein Caffeine 8

9 Important Concepts What are the four components of the skeletal system? What are their functions? What are the functions of? What are the 2 layers of? What is the periosteum? What is its function? What is the structure of the osteon? What are the features found in the osteon? Important Concepts What are the 3 types of cells and their functions? What are the functions of cartilage? What are the functions of tendons? What are the functions of ligaments? What are the parts of synovial joints and their functions? What are the hormones involved in growth and homeostasis? Important Concepts What glands produce calcitonin? What glands produce parathyroid hormones? What are the disorders of the skeletal system? How do s heal? What is osteoporosis? What are the risk factors? What can you do to prevent it? Definitions The End Compact Lacunae Osteon Central (Haversian) canal Spongy Epiphysis Diaphysis Periosteum Callus Fibroblasts Osteoblasts Osteocytes Osteoclasts Chondrocytes Growth hormone Parathyroid hormone (PTH) Calcitonin Vitamin D Epiphyseal plate Growth plate Image From: 9