Human Anatomy & Physiology
QueenofQuestion
6BonesStudents.pptx
Skeletal System
Professor Odom
Levels of Organization
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Learning Objectives
List and describe the functions of bones
Describe the classes of bones
Discuss the process of bone formation and development
Discuss the effect of exercise, nutrition, and hormones on bone tissue
Describe how an imbalance of calcium can affect bone tissue
Explain how bone repairs itself after a fracture
Functions of Skeletal System
Supports the body
Provides attachment for muscles to facilitate movement
Protects internal organs and structures
RBC production
Mineral storage
Learning Objectives
List and describe the functions of bones
Describe the classes of bones
Discuss the process of bone formation and development
Discuss the effect of exercise, nutrition, and hormones on bone tissue
Describe how an imbalance of calcium can affect bone tissue
Explain how bone repairs itself after a fracture
Bone Classifications
There are 206 bones in an adult human skeleton
Axial (80) vs. Appendicular (126)
Classifications:
Flat
Long
Short
In terms of shaft length
Sesamoid
Like a seed
Irregular
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Bone Classifications
| Bone Classifications | |||
| Bone classification | Features | Function(s) | Examples |
| Long | Cylinder-like shape, longer than it is wide | Leverage | Femur, tibia, fibula, metatarsals, humerus, ulna, radius, metacarpals, phalanges |
| Short | Cube-like shape, approximately equal in length, width, and thickness | Provide stability, support, while allowing for some motion | Carpals, tarsals |
| Flat | Thin and curved | Points of attachment for muscles; protectors of internal organs | Sternum, ribs, scapulae, cranial bones |
| Irregular | Complex shape | Protect internal organs | Vertebrae, facial bones |
| Sesamoid | Small and round; embedded in tendons | Protect tendons from compressive forces | Patellae |
Learning Objectives
List and describe the functions of bones
Describe the classes of bones
Discuss the process of bone formation and development
Discuss the effect of exercise, nutrition, and hormones on bone tissue
Describe how an imbalance of calcium can affect bone tissue
Explain how bone repairs itself after a fracture
Anatomy of Bone
Epiphysis: end of long bone
Proximal
Distal
Diaphysis: Shaft
Metaphysis: Narrow portion between diaphysis and epiphysis, contains growth plate
Periosteum: outer layer (peri=around, osteum=bone)
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Bone Growth
Growth occurs between the diaphysis and the epiphysis in the epiphyseal plate
Epiphyseal plate contains cartilage until growth is complete
Cartilage growth occurs on distal end of plate while bone is added medially
Diaphysis lengthens
When growth is complete, the plate becomes the epiphyseal line
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Bone External Structure / Markings
| Bone Markings | ||
| Marking | Description | Example |
| Articulations | Where two bones meet | Knee joint |
| Head | Prominent rounded surface | Head of femur |
| Facet | Flat surface | Vertebrae |
| Condyle | Rounded surface | Occipital condyles |
| Projections | Raised markings | Spinous process of the vertebrae |
| Protuberance | Protruding | Chin |
| Process | Prominence feature | Transverse process of vertebra |
| Spine | Sharp process | Ischial spine |
| Tubercle | Small, rounded process | Tubercle of humerus |
| Tuberosity | Rough surface | Deltoid tuberosity |
| Line | Slight, elongated ridge | Temporal lines of the parietal bones |
| Crest | Ridge | Iliac crest |
| Holes | Holes and depressions | Foramen (holes through which blood vessels can pass through) |
| Fossa | Elongated basin | Mandibular fossa |
| Fovea | Small pit | Fovea capitis on the head of the femur |
| Sulcus | Groove | Sigmoid sulcus of the temporal bones |
| Canal | Passage in bone | Auditory canal |
| Fissure | Slit through bone | Auricular fissure |
| Foramen | Hole through bone | Foramen magnum in the occipital bone |
| Meatus | Opening into canal | External auditory meatus |
| Sinus | Air-filled space in bone | Nasal sinus |
Bone Structure: Internal
Internal Structure
Compact (load bearing): densely packed hydroxyapatite
Contains Yellow marrow
Spongy: trabeculae
Better manage stress from multiple directions
Contains Red Marrow
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Bone Structure: Internal
Bone Cavities
Red marrow: site of RBC production
Yellow marrow: filled with adipose
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Bone Structure: Internal
Internal Structure
Compact (load bearing): densely packed hydroxyapatite
Contains Yellow marrow
Spongy: trabeculae
Better manage stress from multiple directions
Contains Red Marrow
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Compact Bone
Organized in Osteons (Haversian System)
Bone (Osseus) Tissues
Osteon (Haversian System): basic structural unit
Central canal/Haversian Canal: contains nerves and vasculature
Concentric lamellae
Pockets in concentric lamellae are lacuna and contain osteocytes
Lacuna are connected to central canal via canaliculi
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Bone Structure: Internal
Internal Structure
Compact (load bearing): densely packed hydroxyapatite
Contains Yellow marrow
Spongy: trabeculae
Better manage stress from multiple directions
Contains Red Marrow
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Spongy Bone
Also contains:
Organized in Osteons (Haversian System)
But in a Trabecular network
Other Important Bone Cells
Important Bone Cells
| Bone Cells | ||
| Cell type | Function | Location |
| Osteogenic cells | Develop into osteoblasts | Deep layers of the periosteum and the marrow |
| Osteoblasts | Bone formation | Growing portions of bone, including periosteum and endosteum |
| Osteocytes | Maintain mineral concentration of matrix | Entrapped in matrix |
| Osteoclasts | Bone resorption | Bone surfaces and at sites of old, injured, or unneeded bone |
Now that we’ve discussed some of the Important Cells related to Bone let’s revisit growth!
Ossification
Ossification is the transition from cartilage to bone (simplified definition)
Types of Ossification:
Intramembranous ossification
Endochondral ossification
Intramembranous Ossification
Intramembranous ossification: compact and spongy bone develops directly from sheets of mesenchymal (undifferentiated) connective tissue.
Where (Examples): flat bones of skull, mandible and clavicle
Remember this??
Connective Tissue Proper: Loose
Loose Connective Tissue
The “packing material” of the body
Fills empty spaces
Cushion & stabilize organs; support epithelia, blood vessels and nerves
Types include
Areolar tissue
Adipose tissue
Reticular tissue
Mesenchyme & Mucous tissue (embryos only)
Adipose
Reticular
Areolar
Connective Tissue Proper:
Loose
Areolar
Adipose
Reticular
Mesenchyme
Dense
Regular
Irregular
Elastic
Fluid
Blood
Lymph
Solid
Bone
Cartilage
Hyaline
Elastic
Fibrocartilage
Produced by the Mesoderm in embryo
Provides multiple uses during development
Intramembranous Ossification
Intramembranous ossification: compact and spongy bone develops directly from sheets of mesenchymal (undifferentiated) connective tissue.
Where (Examples): flat bones of skull, mandible and clavicle
How:
Mesenchymal cells
Osteoblasts
Cluster together to form a ossification center
Secrete Osteoid (uncalcified matrix)
Calcifies (hardens) as calcium phosphate is deposited around osteoblasts
Osteoblasts Osteoclasts
Ossification
Ossification is the transition from cartilage to bone (simplified definition)
Types of Ossification:
Intramembranous ossification
Endochondral ossification
Skeleton Cartilage
Hyaline Cartilage:
Most abundant
Covers articulating surfaces (joints)
Flexible
Fibrocartilage:
Stiff and tough; absorbs force
Found in intervertebral discs and meniscus
Elastic Cartilage:
Least abundant
Most flexible
Found in ear and epiglottis
Review Slide
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Endochondral Ossification
Endochondral ossification, bone develops by replacing hyaline cartilage. Cartilage does not become bone. Instead, cartilage serves as a template to be completely replaced by new bone. Endochondral ossification takes much longer than intramembranous ossification.
Where: all bones except flat bones of skull, mandible and clavicle
How (long bone):
Week 6-8 of embryonic development Mesenchymal cells
Chondrocytes precursor of bones (a)
Perichondrium (a membrane that covers the cartilage) appears (b)
Uncalcified matrix grows
Chondrocytes also grow in size
Matrix begins to calcify
Endochondral Ossification
Endochondral ossification, bone develops by replacing hyaline cartilage. Cartilage does not become bone. Instead, cartilage serves as a template to be completely replaced by new bone. Endochondral ossification takes much longer than intramembranous ossification.
Where: all bones except flat bones of skull, mandible and clavicle
How (long bone):
Matrix begins to calcify
Prevents chondrocytes from receiving nutrients
Chondrocyte death and disappear
Blood vessels invade spaces
Enlarges cavity (eventually becomes medullary cavity)
Initiates the transformation of the perichondrium into the bone-producing periosteum
and brings osteogenic cells
Osteoblasts begin to form
Endochondral Ossification
Endochondral ossification, bone develops by replacing hyaline cartilage. Cartilage does not become bone. Instead, cartilage serves as a template to be completely replaced by new bone. Endochondral ossification takes much longer than intramembranous ossification.
Where: all bones except flat bones of skull, mandible and clavicle
How (long bone):
Osteoblasts begin to form
A periosteal collar of compact bone around the cartilage of the diaphysis
2nd-3rd month of embryonic development primary ossification center forms, a region deep in the periosteal collar where ossification begins (c)
This process continues.
Chondrocytes continue to grow proximally and distally forming the epiphyses and consist of the epiphyseal plate, while osteocytes continue to replace chondrocytes in the diaphysis
Eventually this process occurs in the epiphyseal regions and is referred to as secondary ossification (e)
Cool…we still haven’t answered the question. How do we grow?
Bone Growth
Growth occurs between the diaphysis and the epiphysis in the epiphyseal plate
Epiphyseal plate contains cartilage until growth is complete
Cartilage growth occurs on distal end of plate while bone is added medially
Diaphysis lengthens
When growth is complete, the plate becomes the epiphyseal line
Review Slide
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Bone Growth in Length
The epiphyseal plate is composed of four zones of cells and activity:
Reserve zone
Proliferative zone
Zone of maturation and hypertrophy
Zone of calcified matrix.
Bone Growth in Diameter
This is called appositional growth. Is controlled by the balance of osteoclasts vs osteoblasts which are stimulated by aging and compressive forces as well as hormones
Osteoclasts resorb old bone that lines the medullary cavity
Osteoblasts produce new bone tissue beneath the periosteum.
The erosion of old bone along the medullary cavity and the deposition of new bone beneath the periosteum not only increase the diameter of the diaphysis but also increase the diameter of the medullary cavity. This process is called modeling.
Learning Objectives
List and describe the functions of bones
Describe the classes of bones
Discuss the process of bone formation and development
Discuss the effect of exercise, nutrition, and hormones on bone tissue
Describe how an imbalance of calcium can affect bone tissue
Explain how bone repairs itself after a fracture
Exercise and Mechanical Stress
Mechanical stress stimulates the deposition of mineral salts and collagen fibers.
The internal and external structure of a bone will change as stress increases or decreases so that the bone is an ideal size and weight for the amount of activity it endures.
That is why people who exercise regularly have thicker bones than people who are more sedentary. The bones undergo remodeling as a result of forces (or lack of forces) placed on them.
Resistance training is especially important to slow down the eventual bone loss due to aging and for preventing osteoporosis.
Hormones that affect Bone Growth
Hormones that have a (+) affect on growth:
GH: increases length and mineralization
Thyroxine: stimulates bone growth
Sex Hormones (E2, T): stimulate growth and osteoblasts
Calcitonin: increases kidney excretion of calcium and inhibits osteoclasts
Calcitriol: stimulates osteoclastic activity and increases absorption of calcium in the gut
Hormones that have a (-) affect on growth:
PTH: stimulates osteoclasts and reabsorption of calcium in the kidney
Calcium and Vitamin D
Bone is made of: Calcium phosphate and calcium carbonate
Calcium needs Vitamin D to be absorbed form the intestines
Sources of Calcium: milk, green leafy vegetables, broccoli, and intact salmon and canned sardines with their soft bones. Nuts, beans, seeds, and shellfish provide calcium in smaller quantities.
Sources of Vitamin D: most commonly acquired from sunlight, supplements and fortified milk.
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Solid Supporting Connective Tissue Cartilage & Bone
Provide a strong framework of support & protection for the body as well as mineral sources
Bone-solid component for attachment, protection, minerals, & RBC production
Organic component: collagen
Inorganic component: calcium phosphate in chemical arrangement called calcium hydroxyapatite
Cartilage-articular surface of joints
Hyaline
Elastic
Fibrocartilage
Review Slide
Learning Objectives
List and describe the functions of bones
Describe the classes of bones
Discuss the process of bone formation and development
Discuss the effect of exercise, nutrition, and hormones on bone tissue
Describe how an imbalance of calcium can affect bone tissue
Explain how bone repairs itself after a fracture
Homeostatic Control of Calcium
Thyroid Gland
Parafollicular cells produce Calcitonin (CT)
Cells monitor concentration of calcium in blood & release calcitonin when blood calcium is too high
Kidneys respond to CT by excreting calcium into urine, reducing blood levels
Tone down Ca2+
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Parathyroid Glands
4 small nodules on the posterior surface of the thyroid gland
Produce PTH (parathyroid hormone)
Released when blood calcium is too low
Kidneys respond by keeping calcium in the blood, and by releasing calcitriol aka vitamin D synthesis
Causing GI to increase absorption
Stimulates osteoclasts that dissolve bone to add calcium to the blood
Homeostatic Control of Calcium
Learning Objectives
List and describe the functions of bones
Describe the classes of bones
Discuss the process of bone formation and development
Discuss the effect of exercise, nutrition, and hormones on bone tissue
Describe how an imbalance of calcium can affect bone tissue
Explain how bone repairs itself after a fracture
Fractured Bone Definitions
A fracture is a broken bone.
Closed reduction is when a broken bone is manipulated and set into its natural position without surgery
Open reduction requires surgery to expose the fracture and reset the bone.
It will heal whether or not a physician resets it in its anatomical position. If the bone is not reset correctly, the healing process will keep the bone in its deformed position.
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Fractured Bone Definitions
Closed: skin remains in tact
Open: one end has penetrated through skin (high infection risk)
Transverse: Occurs in transverse plane, straight across
Spiral: Bones are split as result of twisting motion
Communicated: several breaks with small pieces in between each segment
Impacted: compression that has driven one segment into the other
Greenstick: only one side of bone is broken
Oblique: occurs at a angle that is not 90 degrees
It will heal whether or not a physician resets it in its anatomical position. If the bone is not reset correctly, the healing process will keep the bone in its deformed position.
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Fractured Bones
| Types of Fractures | |
| Type of fracture | Description |
| Transverse | Occurs straight across the long axis of the bone |
| Oblique | Occurs at an angle that is not 90 degrees |
| Spiral | Bone segments are pulled apart as a result of a twisting motion |
| Comminuted | Several breaks result in many small pieces between two large segments |
| Impacted | One fragment is driven into the other, usually as a result of compression |
| Greenstick | A partial fracture in which only one side of the bone is broken |
| Open (or compound) | A fracture in which at least one end of the broken bone tears through the skin; carries a high risk of infection |
| Closed (or simple) | A fracture in which the skin remains intact |
Bone Healing
Hematoma
Internal Callus of fibrocartilage
External Callus of hyaline cartilage
Osteoclasts destroy dead osteocytes, osteoblasts create new osseous tissue and cartilage is replaced
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