Bone Tissue Functions

• Bone tissue is a dynamic tissue that is ever-changing, growing, and developing
• Osteology is the study of bone

Functions of Bone Tissue

• Bone provides support and a framework for the human body
• It also supports soft tissues and serves as a region for muscle attachment
• Bone provides protection
• Skeletal muscle attaches to bone to facilitate movement
• Bone is a reservoir for calcium and phosphate, facilitating mineral storage
• Bone tissue releases these minerals into the bloodstream on demand
• Bone plays a key role in electrolyte balance
• Bone maintains acid-base balance by absorbing or releasing alkaline salts
• Hemopoiesis (hematopoiesis) is the process of blood cell formation/production that occurs in red bone marrow
• Yellow bone marrow, associated with bone, is composed of adipose tissue and scattered leukocytes, providing the body with a source of energy
• Osteocalcin, a hormone produced by bone, helps regulate insulin secretion and sugar homeostasis
• Bone absorbs heavy metals from the blood, reducing their effects on the body, detoxifying the body
• Bone can slowly release these compounds via secretion

Organization of the Skeletal System

• The human skeleton comprises 206 bones dispersed throughout the body
• These bones are classified into two major skeletal divisions, the axial and appendicular skeleton
• The axial skeleton includes bones located along the central axis of the body
• They protect and support body structures
• The appendicular skeleton includes bones of the extremities and are involved in movement

Types of Bones in the Human Skeleton

• Bones can be categorized into long, short, flat, irregular, and sesamoid bones, based on shape
• Long bones are longer than they are wide and are typically curved to increase their strength
• The diaphysis is the shaft of the long bone
• The epiphyses are the ends of the long bone and are covered by hyaline cartilage
• The metaphysis is the region in a mature bone where the diaphysis meets the epiphysis, which region contains the epiphyseal plate for bone growth
• Hyaline (Articular) cartilage ia a layer of cartilage covers the ends of a long bone and acts as a shock absorber between bones
• The periosteum is a membrane that surrounds the surface of a bone and composed of 2 layers
• The outer fibrous layer is composed of dense connective tissue, containing blood vessels, nerves and lymphatic vessels that pass into the bone
• The inner osteogenic layer contains elastic vessels and bone cells
• The periosteum is involved in bone development and serves as a site of attachment for ligaments and tendons
• Sharpey's fibers are collagen fibers that anchor the periosteum to the bone
• The medullary (marrow) cavity is an open space within the diaphysis of a bone that contains yellow bone marrow, which serves as an energy source
• In anemia, yellow marrow can revert to red bone marrow to aid in blood cell production
• The endosteum is a membrane that covers and lines the medullary cavity of a bone and contains osteoprogenitor cells and osteoclasts
• Short bones are cube-shaped and are composed of thin plates of spongy bone (diploe) covered by a layer of compact bone tissue
• Examples include the carpals and tarsals
• Flat bones are very thin bones composed of 2 plates of compact bone tissue that encloses a layer of spongy bone or diploe
• They provide protection and offers a greater surface area for tendon and ligament attachment
• Irregular bones have complex shapes like the vertebrae column and facial bones that are also are composed of diploe
• Sesamoid bones are small bones embedded in tendons. The patella is an example

Histology of Bone Tissue

• Bone tissue comprises 5 types of cells embedded in a thickened and hardened matrix
• Bone matrix is composed of approximately 25% water, 25% protein (collagen), and 50% mineral salts (calcium carbonate and calcium phosphate)
• Calcification (mineralization) is the formation of a new matrix
• Mineral salts accumulate over collagen fibers, which provide strength to the matrix
• Collagen fibers are held together by sacrificial bonds that easily break and reform to dissipate energy from force on bones
• Osteoprogenitor (osteogenic) cells are unspecialized cells derived from mesenchyme undergoing rapid cell division
• They develop into osteoblasts and are located near blood vessels in the periosteum and endosteum of bone
• Osteoblasts secrete collagen and materials to build bone tissue but have lost the ability to undergo cell division
• Osteoblasts on the surface of bone tissue surrounded by matrix are referred to as osteocytes
• Osteocytes are mature bone cells that have lost the ability to divide and do not secrete bone matrix
• They are involved in nutrient/waste exchange between bone and blood
• Osteocytes regulate the daily activities of bone tissue and serve as stress sensors to monitor bone overload
• Bone lining cells are thought to help maintain the health of bone matrix
• Osteoclasts are involved in bone resorption (the destruction of bone matrix) and play a key role in bone growth and repair
• They release acids and enzymes that degrade bone tissue and contain a ruffled border that increases surface area of the cell, increasing enzyme release and bone degradation
• The two types of bone tissue are compact or spongy Bone
• Compact bone forms the external layer over all bones in the body and makes up the diaphysis of long bones
• Compact bone is composed of repeating Haversian Systems (osteons)
• A Haversian System is structured around a Haversian (Central) canal, that runs longitudinally in bone
• The Haversian canal contains blood vessels and nerves
• Lamellae are rings of matrix in bone composed of mineral salts (calcium carbonate and calcium phosphate)
• Volkmann's canals run horizontally in bone tissue and contain blood vessels and nerves
• Lacunae are small spaces in the lamellae of compact bone, where Osteocytes are located
• Canaliculi are small channels extending from lacunae, serve as passageways through which nutrients and wastes can pass
• Spongy bone tissue contains many open spaces and is composed of thin plates of bone known as trabeculae but does not contain haversian systems
• The spaces between trabeculae are filled with red bone marrow involved in blood cell production
• Osteocytes are located in the trabeculae
• Short, flat, and irregular bones, as well as the epiphyses of long bones contain spongy bone tissue, specifically found in the sternum, ribs, skulls, and vertebrae
• Bone is supplied with a large amount of blood via nutrient arteries that carry blood into the diaphysis of long bones through nutrient foramina
• Epiphyseal arteries carry blood into the epiphyses of a bone

Bone Formation (Ossification)

• Bone is a dynamic tissue that is always changing; Ossification is the process by which bone forms
• There exist 2 Patterns of Ossification in the Human Body
• Intramembranous Ossification is the process of bone directly forming on/over loose fibrous connective tissue, without a cartilage stage
• This process occurs in only a few developing bones and the bones formed from this process are soft at birth
• The clavicle, mandible, and skull bones form in this fashion
• Endochondral Ossification is the process of bone formation over hyaline cartilage, of which manner most of the human bones form in

Bone Growth

• Bone growth via length ends before the age of 25, but bones thicken throughout life
• Bone length growth may stop earlier in females than in males
• The epiphyseal plate, a layer of hyaline cartilage in the metaphysis of a growing bone is where growth happens
• The epiphyseal plate is the only area in a bone where length growth can occur
• Eventually, cells in the epiphyseal plate stop dividing and bone tissue replaces the cartilage, producing a remnant known as the epiphyseal line
• Fractures of the epiphyseal plate can result in a cessation of bone growth, causing the fractured bone to be shorter than its counterpart as bone growth usually stops before the age of 25
• Bone growth in thickness occurs as osteoblasts secrete new matrix to the periosteum of bone

Hormonal Regulation of Bone Growth

• Human Growth Hormone (HGH) is secreted by the pituitary gland and regulates bone growth prior to puberty; oversecretion leads to gigantism whereas undersecretion may lead to dwarfism
• Estrogen and testosterone stimulate changes in the human skeleton during puberty, causing a growth spurt, and stimulates the skeleton to develop typically
• Thyroid hormones play a role in bone growth and development

Bone Remodeling

• Bone is an ever-changing type of tissue
• Bone remodeling removes worn and injured bone tissue, replacing it with new, healthy tissue
• Osteoclasts resorb old bone matrix and secrete protein-digesting enzymes and acids
• Once old bone is removed, osteoblasts secrete new matrix
• Alkaline phosphatase, an enzyme, regulates formation of calcium carbonate and calcium phosphate and is needed for bone remodeling
• Bone remodeling relies on vitamins and minerals: including calcium, vitamin C, vitamin D, and vitamin A
  • Calcium provides, well calcium
  • Vitamin C assists formation of collagen fibers
  • Vitamin D facilitates calcium absorption
  • Vitamin A maintains the balance between bone resorption and deposit

Fracture

• Fracture refers to any break in a bone
• Repair of a fracture is a slow and painful process
• The clavicle is the most commonly broken bone

Bone and Calcium Homeostasis

• Bone is the major calcium reservoir in the body, storing 99% of the body's calcium
• Calcium in the human body regulates muscle contraction, impulse formation and conduction in the nerve tissue, and blood clotting
• Parathyroid Hormone (PTH) stimulates osteoclasts to release calcium into the blood when needed
• Calcitonin secreted by cells in the thyroid gland is stimulated when calcium levels rise above normal in the bloodstream
• Calcitonin responds by decreasing osteoclast activity while increasing osteoblast activity, reducing calcium levels in the bloodstream

Surface Markings

• Bones contain surface features that serve as attachments, openings, depressions, etc
• The skeleton compromises 206 bones that are divided into the Axial and Appendicular portions

The Skull

• Compromised of 2 major regions: the cranium and the facial region
• Bones of the Cranium:
  • Frontal Bone
  • Parietal Bones form the majority of the sides of the skull
  • Temporal Bones
    • Temporal Squama forms the temple
    • Zygomatic Arch connects to the zygomatic arch to form part of jaw
    • Carotid Canal permits the Carotid artery to pass through; can hear heartbeat close to the ear
    • Jugular Foramen permits the jugular vein and 3 cranial nerves to pass here
    • Mandibular Fossa forms part of the temporomandibular joint (TMJ)
    • Temporomandibular joint rests between the temporal bone and mandible
    • Mastoid Process-bump behind the ear
    • Styloid Process-site for neck, tongue muscles and ligaments that hold the hyoid bone in place
  • Occipital Bone rests ate the back of skull
    • Foramen Magnum is the site where the spinal cord passes through to attach to the brain
  • Sphenoid-forms the bat in the middle of the skull and articulates with all cranial bones; the keystone bone of the cranium
    • Sella Turcica surrounds and holds the pituitary gland in place
  • Ethmoid bone is at the front of the skull and forms upper portion of nasal cavity and part of the orbits
  • Connects to all of the bones of the skull and face
    • Cribriform Plate forms the roof of the nasal cavity and contains the olfactory foramina through which olfactory nerves pass
    • Perpendicular plate is part of the nasal septum
  • Major Sutures of the Skull:
    • Coronal suture separates the frontal bone and the parietal bones
    • Lambdoid suture separates the parietal bones from the occipital bone
    • Squamous suture separates the temporal bones from the parietal bones
    • Sagittal suture separates the parietal bones from each other
  • Developmental Aspects of the Skull
    • The bones of the skull develop via intramembranous ossification
    • The bones of the skull are not fully ossified at birth, instead, the bones are composed of fontanelles (soft spots) which allow the infant's head to be compressed during birth and accommodate brain growth
  • Facial Bones of the Skull
    • Nasal Bones form the bridge of the nose and are primarily cartilage in composition
    • Vomer is an unpaired facial bone that forms part of the nasal septum
      • Deviated nasal septum is a physical disorder in which the vomer is pushed to one side or another, often caused by face trauma
    • Maxillae are the paired bones that form upper jaw; holding the upper teeth and forms the borders of cavities: the roof of the mouth, the floor of the nose and the floor of the orbits
      • Cleft palate is a condition in which the maxillary bones are not joined, leading to cleft lip
    • Zygomatic Bones form cheek bones
    • Mandible is the largest/strongest bone of face; forming the lower jaw, holds the lower teeth, and is the only movable skull bone
      • Mental foramen is passageway for nerves to the chin
    • Lacrimal Bones are smallest/most fragile of the face
      • Lacrimal fossa allows tears to drain from eye -> nasal cavity
    • Palatine Bones form the underside of the nasal cavit/part of the orbits
    • Paranasal Sinuses: open spaces in some skull bones; filter incoming air and provide tone to your voice
    • Hyoid Bone is a movable base for tounged, and the only bone that does not articulate

The Vertebral Column

• Region of the Column consists of:
  • 1. Cervical Region-
  • 2. Thoracic Region-
  • 3. Lumbar Region-
  • 4. Sacral Region-
  • 5. Coccygeal Region-
• Normal Curves of the Column
  • 1. Cervical Curve (posteriorly Concave), Lumbar Curve (Posterior Concave)
  • 1. Thoracic Curve (Posterior Convex), Sacral Curve (Posterior Conves)
  • These curves provide optimal structure
• Vertebrae: bones of the spinal column
  • Intervertebral Discs form cartilage betw the vertebrae: -Composed of inner gelation (pulpous) and annulus fibrosis -Disc serves as shock-absorber
  • Body (Centrum) provides weight support
  • Vertebral arch also bears support
  • Vertebral Forament allow a passageway
  • Intervertebral Foramina allow for the passage of nerves
  • Processes on the bones
    • Spinous Process
    • 2 Transverse Processes
    • Articular Processes
• Cervical Vertebrae are smallest and their processes are bifid
  • The Atlas is located here-does not have a spinous process.
  • The Axis has Dens (Odontoid Process) pivot for skull rotation
• Thoracic Vertebrae are attached to ribs and the foremen is circular
• Lumbar Vertebrae is the largest of Vertebrae, used for support
  • The foremen processes are triangular

The Skeleton

• Sacrum is a triangular bone of 5 fused vertebrae
  • Nerves and vessels pass through the Sacral Foremen
• The Coccyx is useless
• Major Regions of Sternum:
  • Manubrium is attached to the clavicle at the clavicular notch
  • The Jugular notch processes superior
  • The Body attaches at at ribs 2-7
  • As you age, Xiphoid process cartilage hardens
    • Abdominal muscles attach to the sternum, used as Landmark for CPR

Ribs

• There are 12 Pairs of Ribs
• Ribs -The cartilage of The True attaches directly to sternum -The cartilage of The False does attach to the sternum -The Floating does not attach to the sternum -The Head attaches to vertebrae -The shaft forms the length of the rib

The Appendicular Skeleton

• The clavicle articulates wt Acromial Extremit
• Acromion forms (upp portion) the Acromiioclavic joint w/ the clavicle
• The Glenoid Cavity, which is also known as a fossa creates connection with the shoulder joint when attached by the humerus
• The Humerus joints at the glenoid cavity forming jjoint
  • Greater Tuburcle for main muscles to attach
  • Lesse Tuburcle has muscles attach here too with smaller muscles
  • Deltoid Tuberosity serves as a attachment for muscles
  • Olecrannon Fossa forms the elbow joint
• Medial/Lateral Epicondyles form muscles to form the bones The Olecranon PRocess connects the elbow to the ulna, and Radial tuberosity is a site attachemtn

The Hand

There are 8 Carpal bones form to form the wrist

• The Metacarpals of five bones that form the palm
• Each hands has 14 Phalanages, which that form the finger
• The Sacroliac oint is the place where the sacrumm and illium
• Obturator foremen-large vessel w/ nerves -A title acetabulum is a socket that houses the femus/ thigh Bone

Pelvic structure

• Ischuim lies w/w large foramen vessels and membranse
• The pubis has the pubic symmetry from
• The Pubis w/ symphysis is held together by fibrocartilage-forming the arch
• The female pubis is wider to produce child birth
• Femur joins to the pelvic through head and femus
• The medial side of the femur is greater in women and greater change w/knee
• The Patella increases weight b/g
• The Fibula has attaches to the tibia as the patella attaches to bone.

The Foot structure

• Talus-comatins the tarasl bone
• Metatarsus- composed of metatarsal bones
• Phalanges is also known as toes
• Arches of the foot-support

Joints

• Where bones articulate to contact w/ each other
• There ar e2 joints:
  • (1)They serve for stability: by holding structure to each other
  • (2) They assist with movement
• The structure of them are determined if by their lack of synovial cavity (A, and B) or (C) synocial

The three subcategories

• A) Fibrous- no synonial cavity: they hold together (ex by fibrous connnective tissuee
• B) Cartilage- no synonial caviv- they hold togeteh as synorial or no synovial cavity Gliding: bones move sde to side

Types of synotivial Joints (there are 6 types; A-F)

- (A) Gliding- bones move side by side to side
- (B) Hinge - convex meet concave
- (C) Pivot -Rounded portion and rings meet each other
- (D) Condlyoid- Conlyde goes to elliptical bone
- (e) a Saddle meets a saddle
- (F) A ball of one meets another

Skeletal disorder ( there are 6 discussed from A-G, and one from C-F)

• A- Ostieporosis is characterized by prone to holes, which leads to fracture: it may be reversed from Catium
• B - Pagers occurs where the body weaknes
• C- Hyaline Cart is osteititis
• D- RIcktes/osteomalaica: from lack of vitamin D is helped from vitamin D milk -E - Can be repaired from surgery From C-F: Spine problems from Scoliosis, Kypnosis, Lordosis