LE2 (COMPANA LAB)

Skeletal system

• Body’s central framework

• Consists of bones, cartilage, ligaments and tendons

• Accounts for about 20% of the body weight

300

A baby body’s has about ____ bones at birth

206

These eventually fuse to form the _______ bones that adults have

Long bones, Short bones, Flat bones, Sesamoid bones, Irregular bones

Classification of bones

Long bones

femur, humerus, tibia, radius, phalanges

Short bones

carpals, tarsals

Flat bones

sternum, cranial bones (frontal, parietal), ribs, scapula

Sesamoid bones

patelia, small sesamoid bones in hands and feet

Irregular bones

vertebrae, sacrum, mandible, sphenoid

Bone is more than just a hard structure-It’s a living tissue that grows, repairs, and adopts! With blood vessels, nerves, and active bone cells, your skeleton constantly renews to keep you strong and healthy

Is bone a living tissue

1. Axial skeleton

2. Appendicular skeleton

Divisions of the skeletal system

• Forms the central axis of the body

• Skull, ossicles at the middle ear, vertebral column, and the thoracic cage (ribcage) 

Characteristics of the axial system

to provide support and protection for the brain, the spinal cord, and the organs in the ventral body cavity

Function of axial skeletal

1. Skull

2. Vertebral column 

3. Rib cage

3 main bone groups of the axial skeleton

• bone protective cavity for the brain

• Consists of 22 bones

Skull

sutures

join the junctions of the skull bone 

1. Cranial bones

2. Facial bones

3. Auditory ossicles 

Categories of skull bones 

8

Amount of cranial bones

14

Amount of facial bones

6

Amount of ossicle (References can vary)

Frontal bone (1)

Parietal bone (2)

Sphenoid bone (1)

Temporal bone (2)

Occipital bone (1)

Ethmoid bone (1)

Types: 6

Units: 8

Cranial bones w/ how many types and units

Fontanelle

spots on an infant’s head where the bony plates that make up the skull have not yet come together

Nasal (2)

Lacrimal (2)

Inferior nasal concha (2)

Maxilla (2)

Mandible (1)

Palatine (2)

Zygomatic (2)

Vomer (1)

Types: 8

Units 14

Facial bones w/ how many types and units

No, teeth lack the ability to regenerate and heal

are teeth bones?

Ossicles

three tiny bones in middle ear collectively called 

malleus (hammer) -2

incus(anvil) -2

stapes(stirrup) - 2

Types: 3

Units: 6

Auditory bones w/ how many types and units

foremen magnum

large opening at the base of the skull

Occipital bone

Foramen magnus is located in the 

passageway for the spinal cord to connect to the brain

Function of foramen magnum

• surrounds and protects the spinal cord

• supports the head

• 26 bones, 24 vertebrae, the sacrum and coccyx bones 

• arched curvature for strength, stability, and flexibility 

Functions of the vertebral column 

• Cervical vertebrae (C1-C7)

• Thoracic vertebrae (Th1-Th12)

• Lumbar vertebrae (L1-L5)

• Sacrum

• Coccyx

Parts of the vertebral column

• Located at neck

• 7 vertebrae

• Small and light

• Small body, larger foramen

• Short and bifid (split)

• supports the head, allows neck movement

Characteristics of Cervical vertebrae

• Located at upper and mid-back

• 12 vertebrae

• Medium size

• Larger, body, smaller foramen

• Larger and pointed

• Protects the heart and lungs, supports the ribs

Characteristics of Thoracic vertebrae

• Located at the lower back

• 5 vertebrae

• large and heavy

• largest body, small foramen

• thick and broad 

• supports body weight, allows bending 

Characteristics of lumbar vertebrae 

Cervical, Thoracic, Lumbar

Part of the vertebrae

Body, vertebral foramen, ars/lamina, spinous process

Cervical vertebrae parts

Body, vertebral foramen, lamina, transverse process, spinous process

Thoracic vertebrae parts

Transverse process, spinous process, vertebral disc, body, lamina

Thoracic vertebrae parts

Body, vertebral column, transverse process, articular process, spinous process, lamina 

Lumbar vertebrae parts 

• First cervical vertebrae of the vertebral column

• Allows the “yes” motion of the head

• named after the titan atlas 

Characteristics of atlas vertebrae

• Second cervical vertebrae of the vertebral column

• Allows “no” motion of the head

Characteristics of axis vertebrae

• Name means “sacred bone”

• Ancient greek arid romans thought it as holy because it protected vital organs and was the last bone to decay after death

• starts as 5 bones, fuse into one super bone during adulthood

Characteristics of sacrum

• means “cuckoo” named after a birds because it looks like a bird’s beak

• mini tail from evolution

• from 3 to 5 small bones fused together

Coccyx

Scoliosis

is an abnormal lateral (side-to-side) curvature of the spine

Kyphosis

is an exaggerated forward curvature of the spine, leading to a hunched or rounded back

rib cage

encloses and protects the organs and thoracic cavity 

1. 12 pairs of ribs with costal cartilages

2. Sternum

Parts of the ribs

true ribs

• first seven bones

• connected to the sternum

false ribs

• next five pairs of bones

• attached to the lowest true rib (7th bone) by cartilage

floating ribs 

• floating than both the true ribs and the false ribs

Costal cartilage

responsible for moving the ribs according to breathing

• Comprised of the upper and lower extremities, which include the shoulder girdle and pelvis

• Consisting of the bones that support the appendages

• There are 126 bones

Characteristics of the appendicular skeleton

1. Pectoral girdle

2. Upper limb

3. Pelvic girdle

4. Lower limb

4 main bone groups in the appendicular skeleton 

• Provides the points of attachment of the upper limbs to the axial skeleton

• consists of the clavicle (or collarbone) in the anterior, and the scapula (or shoulder blades) in the posterior

Characteristics of the pectoral girdle

• Humerus (upper arm)

• radius and ulna (forearm)

• carpals (wrist)

• metacarpals (palm)

• phalanges (fingers)

• allows lifting, grabbing throwing, and fine movements

Characteristics of the upper limb

• hip bone; the ilium, ischium, and pubis

• supports body weight, protects pelvic organs, and connects lower limbs

Characteristics of pelvic girdle

• Femur (thigh) - longest and strongest bone

• patella (kneecap)

• tibia & fibula (lower leg)

• tarsals (ankle)

• metatarsals (foot)

• phalanges (toes)

• thicker and stronger than the bones of the upper limbs

Characteristics of lower limb

catilage (chondrichthyes) or bone (Osteichthyes)

skeleton of the fish made of either 

• skull

• Vertebrae (trunk and tail)

• Ribs

Axial skeleton of fish

• Pectoral and pelvic girdle

• Bones of the appendages

Appendicular skeleton of fish

• Lack true bones

• Consist of fins, made of bony rays, used for propulsion, stability and steering.

• adapted their fins for specific functions.  pectoral find for “walking” (anglerfish), claspers for reproduction (sharks)

Differences of fishes from other vertebrates 

parts of fish

• has more vertebrae than any other living animal

• each group developed its own variations

• ribs do not join together at the front (no sternum) - to expand to the size of any prey snake swallows

Characteristics of reptile skeleton

skull, vertebrae, and ribs, with only vestigial remnants of the limbs

characteristics of snake skeleton

Because of the quadrate bone (can move horizontally and vertically), and the ligament (stretchy ligament)

Why can snakes eat meals bigger than themselves

Birds

notable for its strength and lightness due to pneumatization (presence of air cavities) 

furcula or wishbone

acts as a spring to store and release energy during wing flapping, contributing to the efficiency of flight

pygostyle

supports the tail feathers, aiding in steering and stability

• fewer bones in their skeleton

• many bones are fused together

What makes birds different from vertebrates

• Located in the pelvic region, between lumbar and caudal vertebrae

• supports the attachment of the spine

• typically 1-5

• fused to form the sacrum

• 5 sacral vertebrae fused to form the sacrum in humans

• None in fishes

• fused into the synsacrum in birds

• Come before the caudal vertebrae in the vertebral column

Characteristics of sacral vertebrae

• Located at the end of the vertebral column (tail region)

• Provides support and structure for the tail

• can be numerous in animals with long nails

• usually not fused, but in birds, it fuses to form the pygostyle

• highly reduced; 3-5 small, fused to form the coccyx

• present in fishes, forms the tail

• fused into the pygostyle for birds

Characteristics of caudal vertebrae

Hyal

refers to structures related to the hyoid (supporting tongue and throat)

Branchial

refers to bons or arches associated with gills in fish, or their derivatives in higher vertebrates

Capsule 

A hollow, enclosing structure that surrounds or protects organs (cartilaginous or bony) 

Arch

curved structure of bone or cartilage, often supporting or protecting organs 

Angle

Point or region where two sides of a bone meet at an angle

Shaft

long, cylindrical midsection of a long bone, between the ends

projections

raised areas or extensions of bone

process

a prominent projection from a bone, often for muscle/ligament attachment

Tubercle 

small, rounded, smooth or slightly rough projection. site for tendon or ligament attachment

tuberosity

large, roughened projection for tendon/muscle attachment. site for tendon or ligament attachment

trochanter 

large, blunt projection unique to femur muscle attachment. . site for major muscle attachment

crest

narrow, prominent ridge of bone

spine

sharp, slender, pointed projection

Condyle 

rounded articular projection at joint surfaces 

epicondyle

raised area above a condyle 

capitulum

rounded, small knob-like projection for articulation

Facet

a small, flat, smooth articular surface where two bones meet

Depressions and openings

Foramen

a hole/opening in a bone for passage of nerves or blood vessels 

Fossa

shallow depression, often for muscle attachment or articulation

fenestra

natural opening in a bone

Meatus

canal-like opening through a bone

sinus

a cavity within a bone, usually air-filled and lined with mucosa

sulcus/groove

narrow trench or depression for nerves/blood vessels 

prefixes and suffixes

Infra-/Supra-

position relative to another structure (bellow / above)

Inter

between two structures

sub-

situated under or beneath