Chapter 6 Reading Guide
Overview
This reading guide is intended to be used with the Open Stax Anatomy and Physiology textbook.
Open Stax Anatomy and Physiology Chapter 6 Reading Guide
6.1: The Functions of the Skeletal System
- Bone (osseous tissue)
- Hard, dense, connective tissue that makes up most of the adult skeleton.
- The support structure of the body also contains:
- ____________ – semi-rigid connective tissue provides flexibility and smooth surfaces for movement
- The _________________ is the body system composed of bones and cartilage; it performs the following functions:
- Body support – skeleton supports the body’s weight
- Facilitation of movement – serves as points of attachment for muscles.
- Protection of internal organs – skull and ribcage
- Production of blood cells – hematopoiesis occurs in red marrow.
- Storage and release of minerals and fat
- Bones store fat in yellow marrow
6.2 Bone Classification
There are approximately ______ bones that compose the adult skeleton.
These five categories are based on shape and function.
- ________ Bones
- Cylindrical in shape, longer than wide.
- Found in arms, legs, and fingers
- Function as levers; move when muscles contract
- Examples include femur, tibia, fibula, metacarpals, phalanges, and metatarsals.
- ________ Bones
- Cube-like in shape
- Provide stability and support, some limited movement
- Carpals and tarsals
- ________ Bones
- Typically, thin and curved.
- Cranial bones, scapulae, sternum, and ribs
- Serve as muscle points of attachment, protect internal organs
- ________ Bones
- No easily characterized shape fits no other classification.
- More complex in shape.
- Examples include the vertebrae and certain facial bones
- The vertebrae support the spinal cord and protect it against compression
- ________ bone
- Small round bones shaped like a sesame seed.
- Form in tendons where significant amounts of pressure are generated in a joint. Protect tendons against compression forces
- Vary in number from person to person. Found in tendons associated with the feet, hands, and knees
- The patella (kneecap) is the only sesamoid bone found in all people
6.3 Bone Structure
- Gross Anatomy of Bone (using a long bone for the example)
• ________ – the tubular shaft
- ________ cavity – the hollow region in the diaphysis, filled with yellow marrow.
- ________ bone – dense, hard osseous tissue makes up the walls of the diaphysis.
- ________ – wider sections at each end of the diaphysis.
- Composed of ________ bone, which is more porous then compact bone, with red marrow filling the spaces inside the spongy bone.
- ________ plate (growth plate) found where epiphysis meets the diaphysis.
- In children, it consists of a layer of hyaline cartilage in a growing bone.
- In adults, the cartilage is replaced by osseous tissue when growth stops, becomes an ________ line.
- ________ – a thin membrane that lines the medullary cavity
- Contains a layer of bone-forming cells with some connective tissue
- ________ – a touch connective tissue sheath that surrounds the outer surface of the bone, except at the joints
- It contains blood vessels, nerves, and lymphatics to nourish compact bone.
- ________ cartilage – thin layer of hyaline cartilage
- Covers the part of the epiphysis that forms a joint with another bone.
- Reduces shock and friction at freely movable joints, lacks blood vessels, and limited ability to repair the damage.
- ________ – a layer of spongy bone lined with compact bone on both sides, only associated with flat bones, skull, and sternum.
Bone Markings
- Three classes of bone markings: (1) articulations (joints) (2) projections, and (3) holes
- ________ – where two bone surfaces meet
- ________ – an area of bone that projects above the bone’s surface.
- ________ – an opening or groove in the bone that allows blood vessels and nerves to enter the bone.
Bone Cells and Tissue
- Bone consists of small numbers of cells embedded in a matrix of collagen fibers, with inorganic salt crystals.
- Calcium and phosphate ions create hydroxyapatite crystals
- These minerals give bone their hardness, strength, and flexibility
- Types of Bone Cells
- ________ cells – undifferentiated stem cells that divide to form osteoblasts. Found in both periosteum and endosteum.
- ____________ form new bone found in the growing portions,
- Synthesize new matrix will become osteocytes.
- Lack mitotic ability
- ____________ – mature bone cells most common cell type
- Located in spaces called ____________
- Maintain the mineral concentration of the matrix via secretion of enzymes, lack the ability to divide.
- Communicate with other osteocytes via long cytoplasmic extensions through channels called ____________ (singular = canaliculus)
- ____________ – cells derived from monocytes and macrophages.
- Multinucleated, breakdown old bone while osteoblasts form new bone
- This process is called bone remodeling.
Compact and Spongy Bone
- Compact Bone
- Dense, stronger than spongy bone
- Found under the periosteum and in the diaphysis of long bones
- Provides support and protection
- The ____________ or Haversian system
- The microscopic structural unit of compact bone.
- Each osteon is composed of:
- Lamellae (singular = lamella) concentric rings of calcified matrix
- A ____________ canal, or Haversian canal
- Contains blood vessels, nerves and lymphatic vessels.
- ____________ canals, or perforating canals
- Occur at right angles to the central canal, extend to the periosteum and endosteum.
- ____________, spaces in which osteocytes are found
- ____________ – transport nutrients to and wastes from the osteocytes
Spongy (Cancellous) Bone
- ___________ bone matrix is not arranged in concentric circles
- ____________ (singular – trabecula)
- A lattice – like network of matrix spikes, appears to have a spongy appearance to the naked eye.
- Form along the lines of stress, provide strength and balance to dense and heavy compact bone.
- Making bones lighter, so movement is easier.
- Contain red marrow, the site of hematopoiesis’s
Blood and Nerve Supply
- ____________ foramen – small openings in the diaphysis, through which arteries, nerves, and veins pass through.
Figure 6.15
Diagram of Blood and Nerve Supply to Bone
Blood vessels and nerves enter the bone through the nutrient foramen.
6.4 Bone formation and development
_____________ (osteogenesis) begins about the sixth or seventh week of embryonic life.
- Two pathways of osteogenesis
- Intramembranous ossification
- Endochondral ossification
- _______________________ ossification
- Compact and spongy bone directly develop from mesenchymal connective tissue
- Undifferentiated cells begin to specialize in specific tissues and spread out
- ________________ centers (sites of osteoblast formation) appear in clusters throughout the early bone tissue.
- _______________secrete ________ which hardens into a calcified matrix.
- Osteoblasts become osteocytes
- Bones of the skull and clavicles form this way
- Endochondral Ossification
- Bone replaces hyaline cartilage template
- More time consuming than intramembranous ossification
- Long bones, and bones at the base of the skull
- Outline of Endochondral Ossification
- Mesenchymal cells differentiate into chondrocytes forming a cartilaginous precursor of the bone
- __________________ (a membrane) forms that covers the cartilage.
- Chondrocytes grow in the center of the model, matrix calcifies
- Chondrocytes die, and surrounding cartilage disintegrates
- Blood vessels invade the spaces while carrying osteogenic cells with them.
- Enlarging spaces form the medullary cavity
- Growing capillaries penetrate the remaining cartilage; the perichondrium transforms into the periosteum.
- Osteoblasts form a periosteal collar of compact bone around the remaining cartilage
- A __________________________ center forms deep into the periosteal collar
- At the same time, chondrocytes and cartilage grow at the ends of the bone. At the same time bone is replacing the cartilage so that only cartilage that remains is at the:
- Articular surface
- Epiphyseal plate
- After birth, the same sequence continues with each of the new centers of activity are referred to as _____________ ossification center.
How Bones Grow in Length
- Cartilage forms on the epiphyseal side of the plate
- On the diaphyseal side, cartilage is ossified resulting in growth in length
- The ______________ zone does not participate in growth but secures the epiphyseal plate to the osseous tissue of the epiphysis
- ______________ zone – makes new chondrocytes to replace those that die at the diaphyseal end.
- Zone of ______________ and hypertrophy
- Older and larger chondrocytes than those in the proliferative zone.
- Cellular division in the proliferative zone and maturation of cells in the zone of maturation results in longitudinal growth of the bone
- Zone of ______________ matrix
- Chondrocytes die due to the calcification of the matrix around them.
- ______________ line – forms when bone growth stops in early adulthood, the chondrocytes in the epiphyseal plate cease dividing and bone replaces all the cartilage.
- Epiphyseal plates are visible in a growing bone.
- Epiphyseal lines are the remnants of epiphyseal plates in a mature bone.
- Appositional growth – bones grow in diameter, which continues after longitudinal growth stops
- Occurs by the process called modeling
- The old bone along the medullary cavity erodes by the activity of osteoclasts.
- The new bone deposits under the periosteum. This process also increases the diameter of the medullary cavity
Bone Remodeling
- The resorption of old or damaged bone takes place where osteoblasts lay new bone to replace it.
- Injury, exercise, and other activities lead to remodeling
- About ______________ of the skeleton is remodeled annually without injury or exercise.
6.5: Fractures: Bone repair
A fracture is any broken bone
- ______________ reduction – the setting of a broken bone without surgery
- ______________ reduction – requires surgery to expose the fracture and reset the bone
Types of Fractures
- ______________ (or simple) – the skin remains intact
- ______________ (or compound) – the broken bone tears the skin open
- ______________ – at right angle to long axis of the bone
- ______________ – any angle break that is not at 90 degrees
- ______________ – bone segments pulled apart due to a twisting motion
- ______________ – several breaks result in many small pieces between two large segments
- ______________ – a fracture in which at least one end of the broken bone tears, mostly occurs in children
Bone Repair
- Stages in Fracture Repair
- ______________ hematoma – clotting blood results in a disruption of blood flow to the bone, cells around the break die as a result.
- __________ formation (stabilizes the fracture)
- An ______________ callus forms a fibrocartilaginous matrix between the broken ends of the bone.
- Simultaneously, an ______________ callus of hyaline cartilage and bone forms around the outside of the break
- Bone remodeling occurs with bone tissue replacing the damaged areas of the fracture.
6.6: Exercise, Nutrition, Hormones, and Bone Tissue
Exercise and Bone Tissue
- Exercise places mechanical stress on the bones
- Mechanical stress stimulates the deposition of mineral salts and collagen into bone tissue.
- As stress increases or decreases, the internal and external bone structure change to match it.
Nutrition and Bone Tissue
- Calcium and Vitamin D
- The body obtains calcium from food; calcium cannot be absorbed in the small intestine without vitamin D.
- Sources of calcium besides milk and dairy products
- Broccoli, intact salmon, canned sardines, leafy green vegetables
- Sources of vitamin D
- Not found naturally in foods must be added.
- Sunlight upon the skin triggers the body to produce its vitamin D.
Hormones and Bone Tissue
- Several hormones play a key role in controlling bone growth and maintain the bone matrix.
- ______________ hormone (GH) – from anterior pituitary gland
- Triggers chondrocyte proliferation at epiphyseal plates
- Calcium retention which improves bone density
- ______________ – from the thyroid gland
- Promotes osteoblastic activity and synthesis of bone matrix
- ______________ hormone (PTH) (from the parathyroid glands)
- PTH stimulates osteoclast proliferation and activity
- The release from the bones into the bloodstream
- Promotes calcium absorption by the kidneys and small intestine
- ______________ (from thyroid gland)
- Inhibits osteoclast activity reduces the release of calcium into the blood.
Read and pay attention to section 6.7: Calcium Homeostasis: Interactions of the Skeletal System and Other Organ Systems
- You are expected to know the following things from reading this section
- Be able to describe the effects of too much or too little calcium on the body.
- Explain the process of calcium homeostasis.
- Outline the calcium homeostasis process as it occurs in the human body. Include all the facts that pertain to this process.