An Introduction to the Skeleton Flashcards by Miyaki Jan Lim

body system that shows broad outlines of vertebrate phylogeny (fossil record)

Skeleton

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Skeletal framework of vertebrates purpose

Shape
Support
Protection
Muscle attachment for locomotion

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Type of skeleton
Primitive trait
Teeth and membrane bones of skull among higher chordates are dermal

Exoskeleton (dermal skeleton)

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Type of skeleton
Distinguishing characteristic of chordates
Appears much earlier in ontogeny in organisms that have both exo- and endoskeletons

Endoskeleton

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components of mainly mineralized connective tissue deposited in collagen (matrix)

Bone
Cartilage
Enameloids
Dentin

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connects bones to bones and holds them in place

Ligaments

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connects muscles to bones

Tendons

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Formation of Mineralized Structures

mesenchyme turns into Fibroblast, Scleroblast, Myoblast

Fibroblast turns into collagen
Myoblast turns into Muscle
Cells

Scleroblast turns into Osteoblast (bone), Chondroblast (Cartilage), Odontoblast (Dentin), Ameloblast (Enamel)

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Steps in Formation of Skeletal Tissues

Fibroblasts -> Fibrils -> Collagen Fibers -> Collagen Bundles -> Dense Connective Tissue -> Deposition of Minerals

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Embryonic skeleton of higher vertebrates (temporary) and main skeleton of lower vertebrates (permanent)

Usually replaced by bone in higher vertebrates

Specialized (avascular) connective tissue of chondrocytes dispersed in spaces (lacunae) in a matrix

No canaliculi and no blood vessels of its own

Cartilage

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cartilage matrix

chondromucin

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Cartilage are surrounded by the __________ which is a dense connective tissue

perichondrium

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Cartilage are Generally mesodermal (mesenchyme) in origin except for what regions

head and gill region (from neural crest cells)

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Steps in Formation of Cartilage

Chondroblast -> mucopolysaccharides in matrix -> formation of perichondrium -> addition of cartilage from perichondrium, fibroblasts and chondroblasts -> transformation to become chondrocytes

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Types of Cartilage

Hyaline
Fibrous
Elastic
Calcified

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Types of Cartilage

most abundant, least differentiated and precursor of replacement bone, found chiefly on articular surfaces of bones

Hyaline

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Types of Cartilage

intervertebral discs and attachment of tendons and ligaments

Fibrous

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Types of Cartilage

in external ear and epiglottis

Elastic

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Types of Cartilage

formed when calcium salts are deposited within the interstitial substance of hyaline cartilage or fibrocartilage

Calcified

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Specialized (vascular) connective tissue made up of calcified bone matrix

Bone

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bones are synthesized and maintained by what cells

Specialized (vascular) connective tissue made up of calcified bone matrix

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what component of bones are the calcium hydroxyapatite crystals composed off calcium, phosphate and hydroxyl ions

Inorganic component

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what component of bones are the type I collagen with amorphous ground substance

Organic component

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Bones are Bound together by water and __________ as cementing substance

mucopolysaccharides

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Types of Bone Cells

Osteogenic cells/scleroblasts Osteoblasts Osteocytes Osteoclasts

Stem cells derived from mesenchyme Give rise to all connective tissues

Osteogenic cells/scleroblasts

Bone formation and growth regulation Secrete organic and mineral substances for ossification

Osteoblasts

Osteoblasts surrounded by its own intercellular deposits Maintain cellular activities of bone tissue

Osteocytes

Contains enzymes for bone resorption (release of ion stores) Contain hormone receptors for its own regulation

Osteoclasts

Functions of Bone

Support of soft tissues and muscles Locomotion Protect vital organs (skull, ribs, vertebrae) Hematopoiesis: RBC production in bone marrow Reservoir of calcium and phosphate

Classification of Bones

Shape Structure Function Origin Position

Classification According to Shape

Long bone Short bones Sesamoid bones Flat bones Irregular bones

Classification According to Shape characteristic of the limbs

Long bone

Classification According to Shape confined to the carpal and tarsal regions

Short bones

Classification According to Shape present near free moving joints

Sesamoid bones

Classification According to Shape found in limb girdles and in the head

Flat bones

Classification According to Shape vertebral column, skull bones that are not flat and hip bones

Irregular bones

Classification According to Shape formed due to additional ossification centers in or near sutures of the flat bones of the human cranium

sutural bone

Classification According to Structure

Compact bone Spongy bone

are parallel to the long axis of bones to minimize likelihood of fracture Characteristics of amniotes Absent in amphibians, a few reptiles and some small insectivores and rodents

Haversian systems

Classification According to Structure Consists of layers (lamelae) or mineralized collagenous bundles arranged concentrically around a haversian canal has a Haversian system that is made up of the canal and its surrounding lamellae

Compact bone

Classification According to Structure Consists of bone trabeculae and bone marrow Present in expanded head of long bones and fills most irregular bones

Spongy or cancellous bone

part of Spongy or cancellous bone form a rigid framework that provides maximum strength at areas of strength

Trabeculae

part of Spongy or cancellous bone occupies the spaces between trabeculae

Bone marrow

Classification According to Bone Development pre-existing connective tissue is replaced by bone

ossification

is any aggregation of mesenchyme that differentiates into some tissue

Blastema

differentiate into fibroblasts which secretes collagens of become scleroblasts that will become osteoblasts and chondroblasts

Mesenchyme cells

Classification According to Bone Development

Intramembranous ossification Intramembranous ossification

Classification According to Bone Development Formation of membrane bones from connective tissue Bones of lower jaw, skull, pectoral girdle, dermal bones and vertebrae of teleosts, urodeles and apodans May be compact or spongy and lamellar or non-lamellar

Intramembranous ossification

Intramembranous ossification process

Mesenchyme cells in the connective tissue becomes osteoblasts -> deposit bone matrix -> becomes osteocytes

Classification According to Bone Development figure

(A) Mesenchymal cells condense to produce osteoblasts, which deposit osteoid matrix. These osteoblasts become arrayed along the calcified region of the matrix. Osteoblasts that are trapped within the bone matrix become osteocytes. (B) Intramembranous ossification in the plastron (ventral shell) of the red-ear slider turtle Trachemys scripta. The plastron of a one-month-old hatchling was stained with alcian blue (for cartilage) and alizarin red (for bone). No cartilage was seen to precede the formation of bone.

Classification According to Bone Development Formation of bone from hyaline cartilage Bone formed is known as cartilage bone or replacement bone

Endochondral ossification

Endochondral ossification process

After cartilage is formed from mesenchyme: Chondrocytes calcify matrix Undergoes apoptosis Perichondrium -> periosteum Blood vessels intrude the matrix and bring in hematopoeitic cells, osteoclasts and osteoblasts -> bone

Intramembranous (Membrane Bones) starting tissues vasculation type of bones produced

Congregated mesenchymal cell (no cartilage) Numerous small blood vessels Many flat bones

Endochondral (Cartilage Bones or Replacement Bones) starting tissues vasculation type of bones produced

Starts with cartilage Avascular Long bones and flat bones

Same constituents as the bone except that the odontoblasts are not trapped in lacunae Frequently coated by enamel Found in the scales of basal ray-finned and elasmobranch fishes and teeth

Dentin

Canaliculi in dentin are called

dentinal tubules

type of bone where the Osteoclasts retreat as they deposit bone but in addition leave no processes or canaliculi in fibrous plates of scales of modern fishes and the cementum of vertebrate teeth

Acellular Bone

a term is first used to denote acellular dermal bone found in fossil heterostracans

Aspidin

Calcium Storage and Withdrawal provide storage for calcium and other mineral salts

Bones

is constantly deposited or withdrawn from storage based on the amount of calcium in the serum

Calcium

Withdrawal of calcium is by regulation of the

parathyroid gland and calcitonin

remodel to accommodate organs that it needs to protect in response to stress, and is thicker in areas of stress Roughened surface areas, bony ridges and other prominences where muscles attach enlarge with sustained muscle use

Skeletal Remodeling

Connect muscles with bones and have a shiny white appearance Offers maximal resistance to the tension created when muscle contracts

Tendons

Continuous with the epimysium of muscles and perichondrium or periosteum of cartilages or bones

Tendons

Connect bone to bone Arrangement is less regular than tendon but are directly continuous with the periosteum

Ligaments

the largest ligament in mammals is the _________ found extending across the neck of herbivores

nuchal ligament

what animals have ossified tendons in their legs

Turkeys

___________ have the same ossified tendons as turkeys millions of years ago

Ornithischian dinosaurs

what type of bone or cartilage are mineralized nodules in tendons and ligaments and can either be endochondral or membranous

Sesamoid cartilages or bones

Site where two bones or cartilages meet Bones are held together by any one or a combination of fibrous, elastic or cartilaginous _______

Joints or Arthrosis

Classification of Joints or Arthrosis

Fibrous joints (synarthroses) Cartilaginous (amphiarthroses) Synovial (diarthroses or true joints)

Classification of Joints or Arthrosis Capable of minimal to no movement Main function is to hold bones together

Fibrous Joints or Synarthroses

Types of Fibrous Joints or Synarthroses

Sutures Syndesmoses Gomphoses

Types of Fibrous Joints or Synarthroses found among flat bones of the cranium

Sutures

Types of Fibrous Joints or Synarthroses found in between two bones

Syndesmoses

Types of Fibrous Joints or Synarthroses specialized joint that hold the teeth in plate

Gomphoses

Classification of Joints or Arthrosis Permits only limited motion Function mainly for stretching or compression

Cartilaginous Joints or Amphiarthroses

Types of Cartilaginous Joints or Amphiarthroses

Hyaline cartilage joint (synchondroses) Hyaline cartilage joint (synchondroses)

Types of Cartilaginous Joints or Amphiarthroses characteristic of growing bone and are lost as the animal matures

Hyaline cartilage joint (synchondroses)

Types of Cartilaginous Joints or Amphiarthroses features of mature skeleton and occasionally ossify with age

Fibrocartilaginous joint (symphyses)

Classification of Joints or Arthrosis Permit a relatively wide range or motion ROM can either be in a single plane or multiple planes Motions that can take plate at joints include flexion, extension, hyperextension, abduction, adduction, rotation and circumduction

Synovial Joint or Diarthroses

Components of a Synovial Joint

Two bones, the ends of which are covered by hyaline cartilage joint cavity joint capsule Other components which are modifications related to form and function of the joint

Components of a Synovial Joint cavity that lies between the two bones

joint cavity

Components of a Synovial Joint capsule that entirely surrounds the joints cavity, extending both proximal and distal to it

joint capsule

is protection and a strengthening structure of the join capsule

outer, fibrous layer

Components of a Synovial Joint secretes the viscous and slick synovial fluid in joint capsule

inner, synovial layer

Types of Synovial Joint Number of articulating surfaces involved

Simple Complex Compound

Components of the Skeleton

Axial skeleton Appendicular Skeleton Heterotopic skeleton

Appendicular skeleton

Pectoral and pelvic girdles Skeleton of paired fins and limbs Skeleton of median fins of fishes

Heterotopic skeleton

Os cordis - deer and bovines Os penis - dogs, basal primates and other mammals Os clitoridis - female mammals Gizzard bone - doves Tongue - bats Gular pouch - South American lizard Diahpragm - camel Syrinx - birds Upper eyelid (adlacrimal or palpebral) - crocodilians Tarsal plate of eyelid - humans Os rostri - swine Cloacal bones - lizards

Axial skeleton

Notochord and vertebral column Ribs and sternum Skull and visceral skeleton

abnormal growth of bone in the non-skeletal tissues including muscle, tendons or other soft tissue.

Heterotopic skeleton

Types of Synovial Joint Shape or form of the articular surfaces

Plane joint Ball-and-socket joint Ellipsoidal join Hinge joint Condylar joint Trochoid or pivot joint Saddle joint