Human Skeleton Overview

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Questions and Answers

Which of the following bones are part of the cranial skeleton?

Ethmoid (correct)

Mandible

Maxilla

Zygomatic

What are the primary functions of the facial bones?

Produce red blood cells

Secure the teeth and anchor facial muscles (correct)

Form the skull

Protect the brain

How many bones comprise the axial skeleton?

136

106

80 (correct)

What bones articulate with the occipital bone?

Temporal and parietal bones Signup and view all the answers

Which cranial bone is shaped like a butterfly and articulates with all other cranial bones?

Sphenoid Signup and view all the answers

What is the primary role of the foramen magnum in the occipital bone?

Provide passage for spinal cord Signup and view all the answers

Which part of the temporal bone surrounds the external acoustic meatus?

Tympanic part Signup and view all the answers

What is found within the cranial cavity for protection?

Brain and organs of hearing Signup and view all the answers

What structures do the cranial bones primarily protect?

Brain and hearing organs Signup and view all the answers

Which cranial bone contains the pituitary gland?

Sphenoid Signup and view all the answers

Which of the following bones are classified as flat bones?

Parietal bones Signup and view all the answers

Which of the following structures is NOT part of the cranium?

Nasals Signup and view all the answers

How many facial bones are included in the human skeleton?

14 Signup and view all the answers

Which of the following best describes the role of sutures in the skull?

Allow for flexibility during growth Signup and view all the answers

What structure does the cribriform plate form?

Roof of the nasal cavity Signup and view all the answers

Which bones are classified as unpaired facial bones?

Mandible and vomer Signup and view all the answers

What is the primary function of the paranasal sinuses?

Lighten the skull and enhance voice resonance Signup and view all the answers

What structures are found in the lateral masses of the ethmoid bone?

Ethmoid sinuses Signup and view all the answers

Which suture connects the frontal bone to the two parietal bones?

Coronal suture Signup and view all the answers

Which bone forms the lower jaw?

Mandible Signup and view all the answers

What do the superior and middle nasal conchae belong to?

Ethmoid bone Signup and view all the answers

Which bones articulate to form the cheekbone?

Zygomatic and maxilla Signup and view all the answers

What is the function of the olfactory foramina?

Transmit olfactory nerves Signup and view all the answers

What does the palatine bone contribute to?

Nasal cavity and orbit Signup and view all the answers

What is the main portion of the maxillary bone known for?

Maxillary sinus Signup and view all the answers

Which of the following bones does not articulate with any other bone in the body?

Hyoid Signup and view all the answers

Which bones are categorized as sutural bones?

Irregular small bones within cranial sutures Signup and view all the answers

What is the role of the alveolar margin of the mandible?

Contains tooth sockets Signup and view all the answers

What is the primary role of the pubis symphysis?

To unite the two pubic bones Signup and view all the answers

Which feature of the femur makes it structurally significant?

It contains fovia capitis which anchors a ligament Signup and view all the answers

What characterizes the fibula compared to the tibia?

It does not contribute to the knee joint Signup and view all the answers

How many tarsal bones compose the tarsus?

7 Signup and view all the answers

What distinguishes the big toe from the other toes in terms of pharanx count?

It has two phalanges Signup and view all the answers

What is the primary function of the olecranon in the ulna?

To prevent elbow hyperextension Signup and view all the answers

Which bones are part of the carpus that articulate with the radius?

Scaphoid and lunate Signup and view all the answers

What is the composition of each os coxa?

Ilium, ischium, and pubis Signup and view all the answers

What feature of the radius allows for its wider distal end?

Styloid process for wrist attachment Signup and view all the answers

What part of the ilium is located as the superior border?

Iliac crest Signup and view all the answers

How many bones are there in the human hand?

27 bones Signup and view all the answers

Which part of the hip bone is known as the postero-inferior component?

Ischium Signup and view all the answers

What is the role of the acetabulum in the pelvic girdle?

To form a socket for the hip joint Signup and view all the answers

What is the length of the vertebral column in an adult of average height?

70 cm Signup and view all the answers

Which part of the vertebrae is responsible for encasing the spinal cord?

Vertebral arch Signup and view all the answers

What type of curvature is associated with the thoracic region of the vertebral column?

Convex Signup and view all the answers

Which ligaments are primarily involved in preventing hyperextension of the spine?

Anterior & posterior longitudinal ligaments Signup and view all the answers

What is the primary function of intervertebral discs?

Cushioning between bony vertebral bodies Signup and view all the answers

What structural feature of the intervertebral disc is responsible for its elasticity?

Nucleus pulposus Signup and view all the answers

Which segment of the vertebral column contains the largest number of vertebrae?

Thoracic Signup and view all the answers

Which statement accurately describes the structure of the vertebral column?

The sacrum and coccyx are fused bones Signup and view all the answers

What is the primary characteristic of the scapulae?

They are thin, triangular, and flat bones. Signup and view all the answers

Which feature of the humerus articulates with the ulna?

Trochlea Signup and view all the answers

What defines the glenoid cavity of the scapula?

It is a shallow and poorly reinforced socket. Signup and view all the answers

How many bones make up the forearm?

Two parallel long bones Signup and view all the answers

Which muscle is associated with the coracoid process?

Biceps muscle Signup and view all the answers

What happens at the surgical neck of the humerus?

It is frequently fractured. Signup and view all the answers

What are the two components of the pectoral girdle?

Clavicles and scapulae Signup and view all the answers

What structure connects the radius and ulna along their length?

Interosseous membrane Signup and view all the answers

What is the main purpose of the clavicles?

To connect the arms to the body and brace them laterally. Signup and view all the answers

Which bone features two condyles that articulate with the forearm?

Humerus Signup and view all the answers

What is the primary function of the spinous process of a vertebra?

For muscle attachment Signup and view all the answers

Which characteristic distinguishes cervical vertebrae from thoracic and lumbar vertebrae?

Presence of a transverse foramen Signup and view all the answers

What unique feature does the atlas vertebra possess?

No body or spinous process Signup and view all the answers

How do true ribs differ from false ribs?

True ribs connect directly to the sternum Signup and view all the answers

Which structure is located between the manubrium and the body of the sternum?

Sternal angle Signup and view all the answers

What is the primary role of the sacrum in the human body?

To connect the lower limbs to the pelvis Signup and view all the answers

Which vertebral feature is designed to accommodate the passage of nerves?

Foramen Signup and view all the answers

Which structure contributes to the weight-bearing function of lumbar vertebrae?

Bodies Signup and view all the answers

What feature of thoracic vertebrae facilitates their articulation with ribs?

Demi-facets Signup and view all the answers

What connects the xiphoid process to the body of the sternum?

Xiphisternal joint Signup and view all the answers

What is the shape of the lumbar vertebral foramen?

Triangular Signup and view all the answers

The coccyx is formed by the fusion of how many vertebrae?

3 or 4 Signup and view all the answers

Which anatomical landmark can be palpated and serves as a reference during medical examinations?

Jugular notch Signup and view all the answers

Which of the following best describes the body of the thoracic vertebrae?

Roughly heart-shaped Signup and view all the answers

Study Notes

Skeleton

206 bones in the human skeleton, making up about 20 percent of body weight
Divided into the axial skeleton and the appendicular skeleton
Axial skeleton: bones of the skull, vertebral column, and rib cage
Appendicular skeleton: bones of the upper and lower limbs, pectoral and pelvic girdles

### Axial Skeleton

80 bones
Most complex part of human anatomy

Skull

22 bones, divided into the cranial and facial bones
Most skull bones are flat bones, with the exception of the mandible
Bones are joined together by sutures
Facial bones form the anterior part of the skull, cranial bones form the rest
Has eye orbits and paranasal sinuses, houses the organs of hearing and balance
It has 85 openings for nerves, blood vessels, and the spinal cord

Cranium

Can be divided into a vault and a base:
- Vault: forms the superior, lateral, and posterior aspects of the skull, and the forehead
- Base: inferior aspect of the skull
Surrounds and protects the brain, the organs of hearing, and balance
Three bony ridges internally divide the cranial base into three areas: the anterior (highest) fossa, middle fossa, and posterior (lowest) fossa

Facial Bones

Form the framework of the face
Contain cavities for vision, smell, and taste
Provide openings for passage of air and food
Secure the teeth
Anchor the muscles of the face

Cranial Bones

Eight cranial bones: the paired parietal and temporal bones, and the unpaired frontal, occipital, sphenoid, and ethmoid bones
Curvature allows for self-bracing, making them strong despite being thin

Frontal Bone

Dome-shaped bone, forms the roof of the orbits and contributes to the anterior cranial fossa
Articulates with the paired parietal bones posteriorly
Notable features: supraorbital margin, supraorbital foramen, and glabella
Left and right frontal sinuses are lateral to the glabella

Parietal Bones

Paired bones, forming the superior and lateral aspects of the skull
Form the bulk of the cranial vault

Occipital Bone

Single bone at the base of the skull, helping to form the posterior aspect of the skull and the walls of the posterior cranial fossa
Attaches anteriorly to the two parietals and the two temporals, and attaches to the sphenoid
Has the foramen magnum: a passage for the spinal cord
Occipital condyles on each side of the foramen magnum form the site of articulation with the first cervical vertebra
External occipital protuberance is a projection at the back of the skull, more prominent in males

Temporal Bones

Paired bones, form the inferior and lateral aspects of the skull and parts of the cranial floor
Located just below the two parietal bones, with three regions:
- Squamous part: flattened, forms the zygomatic process to the cheekbone, mandibular fossa receives the condyle of the mandible
- Tympanic part: surrounds the external acoustic meatus
- Petrous part: on the internal aspect of the temporal bone, contributes to the cranial base, houses the middle and inner ear cavities
Mastoid process: attachment site for some neck muscles
Styloid process: attachment area for tongue muscles and some neck muscles
Several important foramina: jugular foramen, carotid canal, and internal acoustic meatus

Sphenoid Bone

Complex bone, articulates with all other cranial bones
Forms the base of the middle cranial fossa and contributes to the base of the anterior cranial fossa
Central body contains sphenoid sinuses
Three projections:
- Greater and lesser wings: orbits, middle cranial fossa and anterior cranial fossa
- Pterygoid processes: for muscles
Optic foramina: canals for optic nerves
Superior orbital fissure: between greater and lesser wings, cranial nerves for eye movement

Ethmoid Bone

Cube-shaped bone, located between the orbits and the nasal cavities
Cribriform plate forms the roof of the nasal cavity and the floor of the anterior cranial fossa, tiny holes (olfactory foramina) transmit olfactory nerves
Perpendicular plate projects inferiorly to contribute to the nasal septum
Crista galli projects superiorly to attach to the dura mater of the brain
Lateral masses contain ethmoid sinuses
Superior and middle nasal conchae are located medially
Orbital plates are located laterally, contributing to the medial walls of the orbits

Major Cranial Sutures

Four main sutures connecting the cranial bones:
- Coronal suture: frontal bone and two parietal bones
- Squamous suture: parietal bone and temporal bone - Lambdoid suture: occipital bone and two parietal bones
- Sagittal suture: two parietal bones
Sutural bones: tiny irregular bones, can occur within cranial sutures, additional ossification centers that appeared rapidly during fetal development

Facial Bones

14 bones, mandible and vomer are unpaired
Paired bones: maxillae, zygomatic, nasal, lacrimal, palatine, and inferior conchae

Mandible

Lower jawbone, strongest and largest bone of the face
Body is the horizontal part containing the chin, left and right rami join the body at the mandibular angle
Notable features: mandibular notch, coronoid process (insertion of temporalis muscle), mandibular condyle, alveolar margin (contains tooth sockets), mandibular foramina (nerves to teeth in lower jaw), and mental foramina (blood vessels and nerves to chin and lower lip)

Maxillary Bones

Fused medially
Alveolar margins hold teeth of the upper jaw
Palatine processes project posteriorly forming the anterior two-thirds of the hard palate
Notable features: incisive fossa (passage of blood vessels and nerves), frontal processes, and zygomatic processes
Maxillary sinus is located on each side of the main portion of the bone - often gets infected

Zygomatic Bones

Cheekbones
Articulate with the zygomatic processes of the maxilla, frontal, and temporal bones
Contribute to the inferolateral margins of the orbit

Nasal Bones

Two tiny rectangular bones that fuse medially to form the bridge of the nose
Articulate with the frontal bone superiorly and the maxillary bones laterally

Lacrimal Bones

Two fingernail-shaped bones in the anterior, medial portion of the orbit
Articulate with:
- Frontal bone - Ethmoid bone
- Maxillae
Contains a depression (lacrimal fossa) for the lacrimal sac

Orbits

The bones of the orbits are:
- Zygomatic
- Frontal
- Maxilla
- Ethmoid
- Lacrimal
- Sphenoid
- Palatine (orbital process)

Palatine Bones

Two L-shaped bones
Horizontal plates form part of the hard palate
Vertical plates form the nasal cavity and orbit

Vomer

Single thin bone that forms the nasal septum

Inferior Nasal Conchae

Thin curved bones that project medially
Largest of the three pairs of conchae

Paranasal Sinuses

Frontal
Maxillary
Sphenoid
Ethmoid
These are mucosa-lined, air-filled cavities
They lighten the skull and enhance the resonance of the voice
Connect to the nasal cavity, which helps to warm and humidify the incoming air

Hyoid Bone

Only bone of the body that does not articulate with any other bone
Supports the tongue and gives attachment to muscles for swallowing and speech
Horseshoe-shaped with a body and two pairs of horns

Vertebral Column

33 bones, 24 remain separated, 9 fuse forming sacrum and coccyx
Average length 70 cm in adults
7 cervical, 12 thoracic, 5 lumbar, 5 sacral, 3/4 coccygeal
Supports weight, anchors muscles & ligaments, protects spinal cord
Normal curvatures for resilience: cervical and lumbar are concave, thoracic and sacral are convex

Supporting Elements of Vertebral Column

Ligaments: strap-like, support column of bones
Major ligaments are anterior & posterior longitudinal ligaments, continuous bands down front & back of vertebral bodies
Anterior ligament resists hyperextension; posterior ligament resists hyperflexion
Intervertebral Discs: cushioning between vertebral bodies, shock absorbers, 25% of vertebral column length
Consists of nucleus pulposus and annulus fibrosus
Nucleus pulposus provides elasticity and compressibility
Annulus fibrosus holds vertebrae together and resists tension

A Typical Vertebra

Increases in size moving down the column
Includes weight-bearing body and vertebral arch
Vertebral arch: 2 pedicles and 2 laminae
Arch + body enclose vertebral foramen, forming vertebral canal
Pedicles have superior and inferior notches, creating intervertebral foramina

Cervical Vertebrae

7 in total, C1 and C2 are unusual
C3-C7 are typical:
- oval body, broader side-to-side
- short spinous process, split at end (except C7)
- large vertebral foramen
- transverse foramina for vertebral artery passage

Atlas (C1)

No body or spinous process
Posterior and anterior neural arches
Lateral masses with superior and inferior articular facets
Superior articular facets articulate with occipital condyles, enabling “yes” head movement

Axis (C2)

Similar to C3-C7, except for dens or odontoid process (pivot)
Dens is the “missing” body from the atlas

Thoracic Vertebrae

12 in total, ribs attach
Increase in size from first to last
Heart-shaped body with facets for ribs
Circular vertebral foramen
Long, pointed spinous process
Transverse processes have facets for rib articulation

Lumbar Vertebrae

Lower back, major weight-bearing function
Kidney-shaped bodies, increasing in size from top to bottom
Pedicles and laminae shorter and thicker
Flat, short, directly projecting spinous processes
Triangular vertebral foramen
Inferior and superior facets are curved, uniquely orientated

Sacral Vertebrae

5 separate vertebrae fuse into sacrum during adolescence
Articulates with 5th lumbar and laterally with hip bones (sacroiliac joint)
Includes: sacral promontory, transverse lines, sacral foramina, median sacral crest, sacral canal, sacral hiatus

Coccygeal Vertebrae

“Tailbone” = 3 or 4 fused coccygeal vertebrae
Attachment for pelvic ligaments, otherwise mostly useless

Bony Thorax

Thoracic vertebrae + ribs + costal cartilages + sternum
Protects heart, lungs, and major blood vessels
Supports shoulder girdle and upper limbs
Provides muscle attachment area

Sternum

Anterior midline of thorax
Fusion of 3 bones: manubrium, body, xiphoid process
Manubrium articulates with clavicles and 1st rib pair
Body articulates with 2nd to 7th ribs
Xiphoid process provides attachment for abdominal muscles

Ribs

12 per side, all attach to vertebral column
Curve inferiorly and anteriorly
7 true ribs attach directly to sternum
5 false ribs: ribs 8-10 attach via costal cartilages and rib 7
Ribs 11 and 12 are floating ribs

Ribs (cont.)

Typical rib consists of shaft, head, neck, tubercle and costal groove
Head has 2 facets: one articulates with the same-numbered thoracic vertebra, the other with the superior vertebra
Tubercle articulates with the transverse process of the same-numbered thoracic vertebra

Appendicular Skeleton

Pectoral girdle + pelvic girdle + upper and lower limbs

Pectoral Girdle

2 pairs of bones: clavicles and scapulae, forming a circle around upper trunk
Anteriorly: clavicles
Laterally: scapulae
Posteriorly: scapulae
Bones are light and movable, providing muscle attachment for upper limb movement

Clavicles

Collarbones, mildly S-shaped
Insertion points for muscles, brace to push arms laterally
Curvature prevents outward fracture, protecting subclavian artery

Scapulae

Shoulder blades, thin, triangular, flat bones
Between ribs 2 and 7 dorsally
Includes: superior, medial, and lateral borders, spine, acromion (articulates with clavicle), coracoid process (biceps muscle)

Upper Limb

30 separate bones: arm, forearm, wrist, and hand

Humerus

Longest bone of upper limb, the only bone of the arm
Articulates with scapula proximally and radius/ulna distally
Includes: head (fits into glenoid cavity), anatomical neck, greater tubercle, lesser tubercle, intertubercular sulcus, surgical neck (prone to fracture), deltoid tuberosity
2 condyles and 2 epicondyles: trochlea (articulates with ulna), capitulum (articulates with radius)
Ulnar nerve runs behind the medial epicondyle

Forearm

2 parallel bones: radius and ulna
Articulate with humerus, wrist bones, and each other proximally and distally
Interosseous membrane helps maintain space between bones

Ulna

Slightly longer than radius
Includes: olecranon, coronoid process, radial notch, styloid process
Olecranon locks to prevent elbow hyperextension
Radial notch articulates with radius
Styloid process has ligament to wrist

Radius

Head at proximal end, wider distal end
Distal end includes: medial ulnar notch and lateral styloid process

Hand

27 bones in total: carpus, metacarpus, and phalanges

Carpus

8 carpels: only scaphoid and lunate articulate with radius
Remember “So Long To Pittsburgh” (scaphoid, lunate, triquetrum, pisiform), and “Time To Call Home” (trapezium, trapezoid, capitate, hamate)

Metacarpus

5 long bones, distal ends form knuckles
Numbered 1-5 from thumb to little finger
Proximal ends articulate with wrist bones

Phalanges

3 per finger, 2 for thumb; miniature long bones
Numbered 1-5 from thumb to little finger
Include: proximal, middle, and distal (except thumb, which only has proximal and distal)

Pelvic Girdle

Attaches lower limbs, transmits weight, supports pelvic visceral organs
Forms a complete circle
Left and right hip bones (coxal bones) unite anteriorly and with sacrum posteriorly
Each os coxa consists of 3 fused bones: ilium, ischium, pubis
Acetabulum forms the socket of the hip joint

Ilium

Largest flaring bone of os coxa
Includes: iliac crest, iliac spines, pelvic brim
Body of ilium joins ischium and pubis anteriorly

Ischium

Postero-inferior part of hip bone
Superior body joins ilium, inferior ramus is thinner
Ischial tuberosity is the bony prominence we sit on

Pubis

Anterior part of os coxa
2 pubic bones unite at pubic symphysis
Includes: pubic crest, obturator foramen

Lower Limb

Thigh, leg, and foot

Thigh

Femur: largest, longest, strongest bone
Includes: head, fovea capitis (ligament attachment to acetabulum), neck, linea aspera, lateral and medial condyles, lateral and medial epicondyles, patellar surface
Greater and lesser trochanters are muscle attachment sites

Leg

2 parallel bones: tibia and fibula
Interosseous membrane and proximal/distal tibiofibular joints keep bones rigid
Fibula does not contribute to the knee joint
Tibia: transfers weight from femur to foot, strong and large
Includes: medial and later condyles, anterior border, tibial tuberosity (patellar ligament attachment)
Fibula: includes head and lateral malleolus

Foot

Total of 26 bones: tarsus, metatarsus, and phalanges

Tarsus

7 tarsal bones, largest is calcaneus (heel bone), second largest is talus (ankle joint)

Metatarsus

5 miniature long bones, numbered 1-5 (medial great toe is 1)