Chapter 11 Skeletal System

Points to Ponder What are the 5 functions of the skeletal system? What are the parts of a long bone? How do bones grow, remodel and repair? How are hormones involved in bone growth? What is osteoporosis? How are age, gender and ethnicity determined through skeletal remains? What are the components of the axial and appendicular skeletons? What are synovial joints and what kind of angular movements to they allow?

What are the functions of the skeletal system? 11.1 Overview of the skeletal system What are the functions of the skeletal system? Supports the body Protects the soft body parts Produces blood cells Stores minerals (calcium and phosphate) and fat Allows for movement by attaching muscles

What is the anatomy of a long bone? 11.1 Overview of the skeletal system What is the anatomy of a long bone? Diaphysis – shaft of the bone made of compact bone and filled with yellow marrow Epiphysis – ends of the bone made mostly of spongy bone Articular cartilage – hyaline cartilage found on the ends of long bones Yellow bone marrow – stores fat Red bone marrow – makes blood cells found in spongy bone and flat bones Periosteum – living, outer covering of fibrous connective tissue Ligaments – fibrous connective tissue that connects bones

More detail on bone… Compact bone Spongy bone 11.1 Overview of the skeletal system More detail on bone… Compact bone Composed of osteons with a central canal containing blood vessels Contains living bone cells called osteocytes chambers called lacunae Spongy bone Made of plates with spaces filled with red bone marrow

Where are the 3 types of cartilage found? 11.1 Overview of the skeletal system Where are the 3 types of cartilage found? Cartilage – flexible connective tissue categorized based on the type and arrangement of matrix fibers Types: Hyaline cartilage – ends of long bones, nose, ends of ribs, larynx and trachea Fibrocartilage – disks between vertebrae and in the knee; stronger than hyaline cartilage Elastic cartilage – ear flaps and epiglottis; more flexible than hyaline cartilage

What are the important cells in bone growth, remodeling and repair? Osteoblasts – bone-forming cells Osteocytes – mature bone cells that maintain bone structure derived from osteoblasts Osteoclasts – bone-absorbing cells Chondroytes – cartilage-forming cells

11.2 Bone growth, remodeling and repair How does bone develop? Ossification - the formation of bone in two distinct ways: Intramembranous ossification - bone development between sheets of fibrous connective tissue; used in flat bones Endochondrial ossification – cartilage is replaced by bone; used by most bones

How does endochondral ossification occur? 11.2 Bone growth, remodeling and repair How does endochondral ossification occur? 1st Cartilage model – chondrocytes lay down hyaline cartilage in the shape of the future bones 2nd Bone collar formation – osteoblasts secrete bone matrix and results in a collar made of compact bone 3rd Primary ossification center – osteoblasts are brought interiorly by blood and lay down spongy bone 4th Secondary ossification sites – bone centers in the epiphyses formed after birth 5th Epiphyseal plate – a cartilage band that acts as a growth plate that allows bones to lengthen

Visualizing endochondral ossification 11.2 Bone growth, remodeling and repair Visualizing endochondral ossification

11.2 Bone growth, remodeling and repair How do bones lengthen?

How do hormones affect bone growth? 11.2 Bone growth, remodeling and repair How do hormones affect bone growth? Growth hormone (GH) – stimulates general bone growth and the epiphyseal plates Sex hormones – increases growth during adolescence Vitamin D – converted to a hormone to allow calcium absorption in the intestine

What is bone remodeling and what is its role in homeostasis? 11.2 Bone growth, remodeling and repair What is bone remodeling and what is its role in homeostasis? Bone remodeling – bone renewal at a rate of up to 18% per year Remodeling allows bones to respond to stress Regulates the calcium in the blood through hormones: Parathyroid hormone (PTH) – increases blood calcium by accelerating bone recycling Calcitonin – decreases blood calcium

Health focus: Osteoporosis 11.2 Bone growth, remodeling and repair Health focus: Osteoporosis Osteoporosis – bones are weakened due to a decreased bone mass Bone reabsorption exceeds absorption usually by age 40 Risk factors: women, white or Asian, thin, family history, early menopause, smoking, diet low in calcium, excessive caffeine or alcohol consumption and a sedentary lifestyle Can lead to fractures and other complications Can be treated with drugs, hormones and lifestyle change

11.2 Bone growth, remodeling and repair Steps in bone repair Hematoma (6-8 hrs.) – blood clot formed between broken bones Fibrocartilaginous callus (~ 3 weeks) – cartilaginous callus forms between broken bones Bony callus (3-4 months) – cartilaginous callus is turned to bone Remodeling – old bone tissue is replaced by new bone tissue

11.2 Bone growth, remodeling and repair Bone repair

The 206 bones of the skeleton 11.3 Bones of the axial skeleton The 206 bones of the skeleton

Science focus: Skeletal remains 11.3 Bones of the axial skeleton Science focus: Skeletal remains Characteristics to be determined: Age: approximated through dentition, studying areas of bone ossification and joint condition Gender: pelvic bone is best used, thickness of long bones, skull characteristics Ethnicity: difficult to tell but skull characteristics are most useful

The axial skeleton Skull – made of cranium and facial bones Hyoid bone 11.3 Bones of the axial skeleton The axial skeleton Skull – made of cranium and facial bones Hyoid bone Vertebral column – vertebrae and intervertebral disks Rib cage – ribs and sternum

The skull – the cranium Cranium Protects the brain Composed of 8 bones 11.3 Bones of the axial skeleton The skull – the cranium Cranium Protects the brain Composed of 8 bones Some contain sinuses

Bones of the face and the hyoid bone 11.3 Bones of the axial skeleton Bones of the face and the hyoid bone Facial bones Mandible Maxillae Zygomatic bones Nasal bones Hyoid Only bone that does not articulate with another bone

The vertebral column Types of vertebrae Intervertebral disks 11.3 Bones of the axial skeleton The vertebral column Types of vertebrae 33 vertebrae Cervical (7) Thoracic (12) Lumbar (5) Sacrum (5 fused) Coccyx (4 fused into tailbone) Intervertebral disks Fibrocartilage between vertebrae

The rib cage Ribs – protects heart and lungs Sternum 11.3 Bones of the axial skeleton The rib cage Ribs – protects heart and lungs Flattened bone originating from the thoracic vertebrae 12 pairs: 7 pr. true ribs 3 pr. false ribs 2 pr. floating ribs Sternum Known as the breastbone

The appendicular skeleton 11.4 Bones of the appendicular skeleton The appendicular skeleton Pectoral girdle and upper limb Pelvic girdle and lower limb

The appendicular skeleton 11.4 Bones of the appendicular skeleton The appendicular skeleton Pectoral girdle Scapula and clavicle Upper limb Arm and hand bones

The appendicular skeleton 11.4 Bones of the appendicular skeleton The appendicular skeleton Pelvic girdle coxal bone Lower limb Leg and foot bones

Types of joints (where bones meet bones) 11.5 Articulations Types of joints (where bones meet bones) Fibrous – usually immovable such as the sutures between cranial bones Cartilaginous – tend to be slightly movable such as the intervertebral disks Synovial – freely movable joints such as the ball-and-socket hip and shoulder joints and the knee joint

Anatomy of a synovial joint 11.5 Articulations Anatomy of a synovial joint

Summary of synovial joints movements 11.5 Articulations Summary of synovial joints movements Flexion – decrease in joint angle Extension - increase in joint angle Adduction – body part moves toward midline Abduction – body part moves away from midline Inversion – sole of foot turns inward Eversion – sole of foot turns outward

Visualizing synovial joints movements 11.5 Articulations Visualizing synovial joints movements