SKELETAL SYSTEM AXIAL SKELETON CHAPTER 7 Honors Biology.
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Transcript of SKELETAL SYSTEM AXIAL SKELETON CHAPTER 7 Honors Biology.
SKELETAL SYSTEMAXIAL SKELETONCHAPTER 7
Honors Biology
Skeletal System
Composed of:1. Bones2. Cartilage3. Joints4. Ligaments
~ 20% of body mass Divided into axial &
appendicular
Axial Skeleton
80 bones in 3 regions: Skull Vertebral column Thoracic cage
Functions of the Axial Skeleton1. Supports head, neck, and trunk2. Protects brain, spinal cord, and organs
of the thoracic cavity
The Skull
Formed by: Cranium
1. Enclose & protect brain2. Attachment sites for head & neck muscles
Facial bones1. Form framework of face2. Contain cavities for special sense organs3. Provide openings for air & food passage4. Secure the teeth5. Anchor muscles of facial expression
Sutures
Interlocking joints between flat bones (cranium)
Newborn Skull
fontanels: “soft spots” present between cranial bones made of unossified mesenchyme eventually replaced by mature bone function: provide some flexibility to
fetal head allowing skull to change shape as it passes thru birth canal
Cranium
8 bones : 2 paired: parietal, temporal 4 single: frontal, occipital, ethmoid,
sphenoid
Frontal Bone
Forms anterior cranium Articulates posteriorly with parietal
bones Parts:1. Squamous
Forms forehead
2. Supraorbital margins3. Forms:
superior wall of orbits Anterior cranial fossa: houses frontal lobes
of brain
Parietal Bones
most of superior and lateral aspects of the skull forming the bulk of the cranial vault
4sutures:1. Coronal suture
Parietal bones meet frontal
2. Sagittal suture Rt parietal bone meets lt parietal bone
3. Lambdoid suture Parietal bones meet occipital bone
4. Squamous suture Parietal bones meet temporal bones
Occipital Bone
Forms most of skull’s posterior wall & base
@ base is foramen magnum “large hole” ↑brain stem, ↓ spinal cord
occipital condyles articulate with 1st vertebra
Temporal Bones
form inferolateral aspects of the skull 3 major parts:1. Squamous 2. Tympanic3. Petrous
Squamous portion : Temporal Bones
abuts squamous suture
Zygomatic process Meets zygomatic bone
anteriorly forming zygomatic arch
Mandibular fossa receives condylar
process of mandible forming the temporomandibular joint (TMJ)
Tympanic part: Temporal Bone
surrounds external acoustic meatus : external ear canal receives sound waves & directs them inward to ear drum
Petrous Portion: Temporal Bone houses middle & inner ear
Sense organs for hearing & equilibrium forms part of base of skull Mastoid Process
“lump” just posterior to ear Attachment site for neck muscles
Styloid Process Needle-like attachment for tongue & neck
muscles
Temporal Bones
Sphenoid Bone
“bat-shaped” spans width of middle cranial fossa
Articulates with every other cranial bone
Contains sphenoid sinuses Superior surface: sella turcica a saddle-
shaped fossa where the pituitary gland sits aka hypophyseal fossa
Sphenoid Bone
Ethmoid Bone
“like a sieve” midline of anterior part of cranial
floor, anterior to sphenoid, posterior to nasal bones
cribiforme plate: forms roof of nasal cavity, the holes of the sieve where olfactory nerves pass from roof of nasal cavity to brain
crista galla: triangular process which serves as pt of attachment for meninges of brain
Ethmoid Bone
perpendicular plate: forms superior portion of nasal cavity
superior & middle nasal conchae: (or turbinate) increase vascular & mucous membrane surface area in nasal cavities: aids in sense of smell, warms, filters & moistens air being inhaled. Filters because the turbinates cause air to swirl as a result inhaled particles strike & become trapped in mucus
“Sometimes when you study anatomy, you start seeing others differently.”
Facial Bones
shape of face changes dramatically during 1st 2 yrs of life: brain & cranial bones expand 1st set of teeth erupt paranasal sinuses enlarge growth of face stops ~16 years old
Facial Bones
14 facial bones:1. 2 nasal bones2. 2 maxillae3. 2 zygomatic bones4. 1 mandible5. 2 lacrimal bones6. 2 palatine bones 7. 2 inferior nasal conchae8. 1 vomer
Mandible
largest & strongest facial bone (lower jaw)
alveolar processes hold lower teeth sockets
mental foramen: dentist numb mental nerve
Maxillae
= upper jaws *articulate with every bone in face
except the mandible form part of floor of orbits, parts of
nasal cavity, & most of the hard palate (bony roof of mouth)
each one has large maxillary sinus alveolar process is small arch that
contains the alveolar sockets for upper set of teeth
Cleft Palate & Cleft Lip
10-12 wks gestation the palatine processes of maxillae typically join
not doing so cleft palate +/- cleft lip speech & swallowing can be affected many ear infections reparative surgery recommended 1st
few wks of life / surgery needs to be completed by 12 – 18 mos b/4 speech: speech therapy & orthodontic care frequently necessary
Zygomatic Bones
“cheekbones”: the temporal process of the zygomatic bone articulates with the zygomatic process of the temporal bone
also part of floor of orbit
Nasal Bones
form part of the bridge of the nose (rest is cartilage)
Lacrimal Bones
thin, about the size of pinky fingernail (smallest bones of face)
part of medial wall of each orbit each contain lacrimal fossa that
houses lacrimal sac: gathers tears nasal cavity
Palatine Bones
L-shaped pair of bones that form the posterior portion of the hard palate & part of floors of nasal cavity & orbit
Vomer
Δ shaped bone on the floor of nasal cavity forming inferior portion of nasal septum
Inferior Nasal Conchae
inferior to the middle nasal conchae of the ethmoid bone forming part of lateral wall of nasal cavity
same function as superior & middle conchae: swirling inhaled air to deposit particulates but not involved in sense of smell
Paranasal Sinuses
In these 4 bones + sphenoid
Mucosa-lined, air-filled with small openings that connect to nasal cavity
Mucosa helps warm & humidfy inhaled air
add resonance to voice
Hyoid Bone
“U-shaped “ *does not articulate with any other
bone in skeleton suspended by ligaments from
styloid process of temporal bone in anterior neck between mandible
& larynx Function: supports tongue *frequently fractured during
strangulation
Hyoid Bone
Vertebral Column
aka spine, backbone 2/5 of person’s height 26 in adult (starts as 33, some fuse
to form sacrum & coccyx) 7 cervical 12 thoracic 5 lumbar 1 sacrum 1 coccyx
Vertebral Column
Fetus has anteriorly concave curve
3 mos old when holds head cervical curve develops
lumbar curve develops as infant sits up, stands, walks
Intervertebral Discs
between bodies of consecutive vertebra under compression they flatten &
broaden harden, less elastic w/aging & narrow
loss of height annulus fibrosus: outer fibrous ring nucleus pulposus: inner soft, highly
elastic
Parts of a Vertebra
Body thicker, anterior portion, weight bearing
portion Vertebral Foramina
contains spinal cord, adipose, areolar CT, blood vessels
Spinous Process 1 of 7 processes, posterior, palpable on
back of body
Transverse Processes: on each side, extending laterally
Vertebrae: 1st & 2nd Cervical Atlas
ring-shaped articulates with
condyles of occipital bone
allows you to nod head “yes”
Axis 2nd cervical v. allows you to
shake head “no”
Typical Cervical Vertebrae
C-3 to C7 smaller than
other v. except coccyx but vertebral foramen largest
all cervical v. have extra foramen: 2 transverse foramen for vertebral a., v., & n.
Typical Thoracic Vertebrae T-1 to T-12 larger &
stronger than cervical v.
distinguishing feature: articulate with ribs (facets on transverse processes of T-1 to T-10
Typical Lumbar Vertebrae
L-1 to L-5 largest &
strongest of the vertebrae
processes are short & thick
Sacrum
triangular bone formed by union of S-1 to S-5
fusion begins ~16, complete by age 30
female: shorter, wider, more curved S-2 to S-3
Coccyx
small triangle formed by
fusion of 4 coccygeal v. (Co-1 to Co-4), start between 20 & 30
females points inferiorly; males it points anteriorly
Thorax
refers to entire chest skeletal part of thorax is thoracic
cage Sternum Ribs
Sternum
aka “breastbone” flat bone in center of anterior
thorax 3 bones that fuse by age 25
Sternum
1. Manubrium superior portion suprasternal notch clavicular notches articulates with
costal cartilage of 1st & 2nd rib
sternal angle: where it articulates with body
Sternum
2. Body middle &
largest portion articulates with
costal cartilage of 2nd thru 10 ribs
Sternum
3. Xiphoid Process
cartilagenous in infancy
not completely ossified until ~age 40
avoid it during CPR
Ribs 12 pairs increase in length 1st thru 7th then
decrease in length to 12th 1st thru 7th ribs (true ribs) have
direct anterior attachment to sternum by strip of hyaline cartilage which contribute to elasticity of thoracic cage
8th thru 10th ribs attach to each other & then to cartilages of 7th rib
11th & 12th ribs: floating ribs
Ribs
all 12 attach posteriorly to vertebrae
Parts of a Rib1. Head2. Neck3. Tubercle 4. Body 5. Costal Angle
Abnormal Curvatures of Spine Scoliosis lateral bending usually in
thoracic region
Abnormal Curvature of Spine
Kyphosis exaggeration of
the thoracic curve
seen in TB of spine, congenital malformation, elderly
