Topic 3_The Human Skeleton I

Topic 3B: The Skeleton I

Introduction

• Overview of bones, cartilage, and ligaments in the human skeleton.

• Reference: Chapter 7, page 19-245 from a specific source.

Section Objectives

Skull Structure

• Cranial and Facial Bones: Identify, describe, and mark notable features.

• Sutures & Sinuses: Understand connections and anatomical structure.

• Bony Boundaries: Describe orbits and nasal cavity structures.

Vertebral Column

• Recognize regions and normal curves, ligaments, and intervertebral discs.

• Discuss structure of cervical, thoracic, and lumbar vertebrae.

• Note the anatomy of sacrum and coccyx.

Thoracic Cage

• Detailed anatomy of the sternum and ribs.

• Distinguish between true and false ribs.

Skeleton Overview

Major Divisions

• Axial Skeleton:

  • Comprises bones of the skull, vertebral column, and rib cage.

• Appendicular Skeleton:

  • Comprises bones of the upper and lower limbs; includes pectoral and pelvic girdles to attach limbs to the axial skeleton.

Human Skeleton Statistics

• Total Bones: 206 bones; contributes to approximately 20% of body weight.

The Skull

Structure

• Comprised of 22 Bones total:

  • Cranial Bones: Enclose the brain, attach to muscles.

  • Facial Bones: Provide framework for face, cavities for senses, openings for air and food passage, anchor teeth and facial expressions.

  • Most skull bones are flat, except for the mandible, which is not.

Sections of the Skull

• Cranial Vault: Upper parts including forehead.

• Cranial Base: Contains bony ridges dividing into anterior, middle, and posterior fossae.

• Contains various cavities, such as nasal and ear cavities.

• Named Openings: 85 openings for major vessels and nerves including foramina and canals.

Cranial Bones

• Types of Bones:

  • Parietal (2)

  • Temporal (2)

  • Frontal

  • Occipital

  • Sphenoid

  • Ethmoid

Frontal Bone

Features

• Forms the anterior portion of the cranium and roof of orbits.

• Contains frontal sinuses, located to the sides of glabella.

• Vertical part: forehead, called squamous region

note:

• supraorbital margin

• supraorbital foramen

• glabella area

  • the smooth area located between the eyebrows, just above the nasal bridge.

Parietal Bones

Features

• Form superior and lateral aspects of the skull.

• Connected through sutures to adjacent bones.

• Major sutures:

  • Coronal: Between parietal and frontal bones.

  • Sagittal: Divides parietal bones.

  • Lambdoid: Between parietal and occipital.

  • Squamous: Between parietal and temporal.

Occipital Bone

Features

• Forms posterior skull artwork.

• Connects with parietal and temporal bones.

• Contains foramen magnum for spinal cord passage.

• 

• Foramen magnum: hole through which brain connects with spinal chord

• Occipital condyles: site of articulation with first cervical vertevrae

  • condyle: rounded part of bone usually for articulation

  • fossa: depression in bone

• External occipital crest: ride down middle of occipial

• External occipital protuberance: bump as bone comes toward spine

• Nuchal lines: ridges on the external occipital bone that provide attachment for muscles and ligaments associated with the neck.

Temporal Bones

Structure

• Covers inferior and lateral surfaces of the skull.

• Positions: Squamous, tympanic, and petrous regions.

• Features include: zygomatic process, external auditory meatus, and mastoid process.

Squamous:

• flattened

• zygomatic process of the temporal bone

• mandibular fossa: recieves condyle of mandible to form jaw joint

Tympanic:

• Tympanic membrane surrounds external acoustic meatus:serves to transmit sound vibrations to the middle ear.

Petrous:

• bump behind ear is called a mastoid process.

Mastoid process: major attachment area for some neck muscles

Styloid process: muscles for tongue and some neck

Sphenoid Bone

Characteristics

• A complex bat-shaped bone contributing to the cranial fossa.

• Key Features: Optic foramina, superior orbital fissure, and sella turcica for pituitary gland.

• keystone bone: because it connects to all the other cranium bones.

• 

• Optic foramina

• Superior orbital fissure

• Foramen rotundum and ovale

• Foramen spinosum

• sella turcica

Ethmoid Bone

Anatomy

• Forms part of the nasal cavity and orbits.

• Contains cribriform plate for olfactory nerves and contributes to nasal septum.

• cribriform plate

  • roof of nasal; cavity, floor of anterior cranial fossa

  • tiny holes (olfactory foramina) allow transmit info to olfactory bulb

• perpendicular plate

  • projects inferiorly to contribute to the nasal septum

• crista galli

  • anchor dura mater of brain

lateral amsses contain ethmoid sinuses

mediallly are superior and middle nasal conchae, which are thin, scroll-like bones that help to filter and humidify the air we breathe.

Major Sutures of the Skull

• Connect cranial bones through the identified sutures: Coronal, Squamous, Sagittal, and Lambdoid.

Squamous suture: parietal and temporal

Coronal: frontal and parietal

Saggital: parietal bones

Lambdoid: occipital and parietal

Sutural bones: tiny irregular obmes, additional ossifcaiton centres that appeared rapidly during fetal devel.

Facial Bones Overview

Number of Bones

• 14 total bones, including:

  • Mandible

  • Maxillary bones (2)

  • Zygomatic bones (2)

  • Nasal bones (2)

  • Lacrimal bones (2)

  • Palatine bones (2)

  • Vomer

  • Inferior nasal conchae (2)

Functions

• Support facial structure, openings for air and food, cavities for sensory organs, and secure teeth.

Mandible Features

• Largest and strongest facial bone.

• Lower jaw, only bone that moves in cranium, allowing for the opening and closing of the mouth during speech and chewing.

• Noteworthy Parts:

  • body: chin,

  • mandibular angle, where it curves up

  • mandibular notch, top of jaw

  • coronoid process, insertion point for temporalis muscle

  • Mandibular condyle, the rounded end of the mandible that articulates with the temporal bone at the temporomandibular joint (TMJ).

  • Alveolar margin contain tooth sockets

  • Mandibular foramina, nerves to teeth startsnear cheek

  • Mental foramina,openings in the mandible that allow the mental nerve and blood vessels to pass through, providing sensation to the lower lip and chin.

Maxillary Bones

Characteristics

• Fused medially, housing sinuses that may become infected.

• Keystone facial bone

• Palatine processes of the maxilla contribute to the formation of the hard palate

• Frontal process: upward projection connect to frontal bone

• Zygomatic process: side projection, connect to zygomatic bone

• Incisive fossa

• Infra orbital foramen: below orbit hole

Zygomatic Bones

• Form cheekbones and articulate with various other bones.

• Connected through zygomatic processes:

  • Project upwards connect to frontal bone

  • Project laterally connect to temporal

  • Project medially and connect to nasal

  “The zygomatic process of the temporal bone, connects to the temporal process of the zygomatic bone.”

and “the zygomatic process of the frontal bone connects with the frontal process of the zygomatic bone.”

Nasal Bone

• Small bones forming the bridge of the nose.

• articulate wit frontal, maxillary, and ethmoid bones

Additional Facial Bones

Palatine Bones

• Form parts of the hard palate and contribute to the nasal cavity and orbit.

  

Vomer

• Thin bone forming a part of the nasal septum.

Lacrimal Bones

• Involved in forming the orbit and housing the lacrimal sac.

  • where tears collect

Inferior Nasal Conchae

• Contribute to the structure of the nasal cavity.

Hyoid Bone

Characteristics

• Located in the neck, supports tongue and is unique as it does not articulate with any other bone.

• Not bone of skull

• Support tongue, attachment for swallow muscles and speech

Orbits and Nasal Cavity

Orbital Structure

• Formed by contributions from seven different facial bones.

• Frontal

• Zygomatic

• Sphenoid

• Lacrimal

• Maxilla

• Palatine

• Ethmoid

Nasal Cavity Anatomy

• Formed by components from different bones and contributes to airflow and respiratory efficiency.

• “Broken noses”

  • cartilage broken

• “Deviated septums”

  • doesnt run along the midline

Paranasal Sinuses

• Air-filled spaces lined with mucous membranes. maximizing skull lightness and enhancing voice resonance.

Major paranasal Sinus containing bones

• Frontal, Maxillary, Sphenoid, Ethmoid.

Vertebral Column Overview

Functions

• Acts as a weight-bearing structure, anchors muscles, and protects the spinal cord.

Composition

• Comprises 33 vertebrae with 24 free and 2 fused structures (sacrum and coccyx).

Major Regions

brekfes lunch dinne.

breakfas at 7, lunch at 12, din at 5

cerv, thora, lum

• Cervical: 7 vertebrae.

• Thoracic: 12 vertebrae.

• Lumbar: 5 vertebrae.

• Sacrum: 1 fused bone.

• Coccyx: fused from 3-4 bones.

Curvatures of the Vertebral Column

• primary, born with

• secondary, after birth

Main Curvatures

• Cervical and Lumbar: Concave.

  • secondary

  • come from first: lift head, then walking

• Thoracic and Sacral: Convex.

  • primary

Abnormal Curvatures

• Can arise from congenital issues or lifestyle factors.

  • Scoliosis

    • abnormal lateral rotation, usually in thoracic area

    • lungs and heart affected by reposition of thoracic cage.

  • Kyphosis

    • hunch back

    • rounding of upper back

  • Lordosis

    • accentuated lumbar curvature- Swayback posture, which can lead to discomfort and pain in the lower back.

      • could be disease, or pregnant, or fat stomach

Supporting Elements of the Vertebral Column

Ligaments

• Play a critical role in maintaining posture and stability.

• Protect against over flection and overextension

Intervertebral Discs

• Act as shock absorbers and cushioning elements.

• Structure: Nucleus pulposus (inner) and annulus fibrosus (outer).

General Structure of Vertebrae

Vertebra Components

• Weight-Bearing Body: Anterior aspect.

• Vertebral Arch: Made up of pedicles and laminae.

• Vertebral canal and foramina: Allow passage for nerves and vessels.

• Spinous process

  • project posteriorly; muscle attachment

• 2 transverse processes

• Paired superior processes

• Inferior articular proceses

Superior and inferior articular processes link vertebrae above & below; smooth, collagen coated facets for articulation

Individual Vertebrae Characteristics

Cervical Vertebrae (C1-C7)

• Unique structures such as transverse foramina and split spinous processes for muscle attachment.

• C₃ to C₇ traditional

• Cervical vertebrae have hole in transverse processs, which allow for the passage of vertebral arteries and veins, playing a crucial role in supplying blood to the brain.

Atlas and Axis

• C1 (Atlas): No body, allowing nodding motion say yes.

• 

  • neural arches

  • no spinous process

• C2 (Axis): Contains dens for rotational movement.

  • allow head movement say no

• 

Thoracic Vertebrae

• T_{1 to} T₁₂

• These vertebrae support the rib cage and protect the thoracic organs, while also allowing for limited movement in the upper back.

• Articulate with ribs and show heart-shaped bodies and longer spinous processes.

• Notches on body and transverse process

  

Lumbar Vertebrae

• Robust structure for load-bearing; unique facet orientations prevent rotation.

• L₁ to L₅

• bodies are kidney shaped, increase in size from top to bottom.

• pedicles and laminae shorter and thicker than other vertebrae

• Spinous processes are flat hatchet shaped

• vertevral foramen is triangular

• 

Sacrum and Coccyx

• Formation from fused vertebrae articulating with pelvis and coccyx; features include sacral foramina and crests.

• Sacrum

  

• Spinal chord stops at about L₁, below that the cauda equina begins, consisting of nerve roots that continue down the vertebral canal.

  • exit through the anterior sacral foramine

  Anterior:

• sacral promontory

• transverse lines

• anterior sacral foramina

Posterior:

• median sacral crest

• posterior sacral foramine

• sacral canal

• sacral hiatus

Coccygeal vertebrae = tailbone 3 or 4 fused coccygeal vertevrae. attachent for some pelvic ligaments

Thoracic Cage Structure

Overview

• Composed of thoracic vertebrae, ribs, costal cartilage, and sternum.

Sternum Anatomy

• Three fused sections:

• Manubrium

  • articulate with clavicles and ribs 1 and 2

• body

  • notches forarticulation with ribs 2 to 7

• xiphoid process.

  • attach some abdominal muscles

Ribs Overview

• True Ribs: Direct sternum attachment.

  • Vertebrosternal

  • ribs 1-7 attach direcyly by individual costal cartilages

• False Ribs: Indirect or no attachment.

  • Vertebralchondral

  • ribs 8-10 attach to sternum indirectly via costal cartilages of rib above and rib7

  • ribs 11 and 12 are not attached anterioirly to sternum (floating ribs)

• Typical rib is a bowed, flat bone.

  • Shaft:

    • main part of rib

    • costal groove: a shallow indentation along the inner surface of the rib that houses the intercostal vessels and nerves.

  • Head:

    • 2 facets. one articulates with the demi fact on the body of the same-numbered thoracic vertebra. other with that on body of superior vertebra.

    • therefore rib 4, would connect to superior vert. 3 and demi facet of 4

  • Tubercle: connects with transverse process of the corresponding thoracic vertebra.

•