A&P @ LCC by Dr. Prince

Ch 7 The Skeleton

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Objectives
  • Selected key terms
  • Name and describe the two subdivisions of the skeletal system
  • Name and identify the bones of the skull and their important markings
  • The bones of the orbit
  • Structure of the vertebral column, its components, normal curvatures, and 3 abnormal curvatures
  • Structure and function of the intervertebral discs
  • The structure of a typical vertebra and know and describe the distinguishing features of cervical, thoracic, and lumbar vertebrae
  • Know and be able to identify the different bones and osseous land marks of the throax
  • Diffferentiate true, false, and floating ribs
  • Know bones and important bone markings of the pectoral girdle
  • Bones and important markings of the upper limb
  • Bone and important markings of the pelvic girdle
  • Know the differences in the male and female pelvis
  • Bones and markings of the lower limb
  • Know the location and function of the different fontanels

Please explain the orbit?
 
The orbit protects the eyeball and its associated structures.  The roof of the orbit is formed by the frontal adn sphenoid bones, the lateral wall by the sphenoid and the zygomatic, the floor by the maxilla, zygomatic and palatine, and the medial wall by the maxilla, lacrimal, ethmoid, and sphenoid bones.
 
What is a fontanel for?
 
A fontanel is a membrane-filled space between the cranial bones of a baby.  Fontanels enable the fetal skull to modify its size and shape as it passes through the birth canal, permit rapid brain growth in infancy, help determine the degree of brain development byu their state of closure, and act as skelletal landmarks.
 
What is the difference between true and false ribs?
 
true ribs are the first 7 pairs and they attach directly to the sternum via costal cartilages.  False ribs are the next 5 pairs the first 3 pairs attach to the sternum via the costal cartilage of rib #7 and the last 2 pair of false ribs are called floting ribs as they have no anterior attachment to the sternum.
 
Describe the principal classifications of bones based on shape.
 
Long bones are greater in length than width
Short bones nearly equal in length and with
Flat bones have two plates of compact bone surrounding spongy bone
Irregular bones have complex shapes
Wormian bones are located in sutures of the skull
Sesamoid bones are located in tendons at joints
 
Desscribe  the differences between the male and female pelvis
 
the female pelvis is specialized for childbirth.  The false pelvis is shallower and the pelvic brim is larger and more oval vs the male heart shaped pelvis.  The pubic arch is greater than 90 vs male that is less than 90.  The ilium is less vertical and the iliac fossa is shallower.  The iliac crest is less curved and the acetabulum are smaller.  the obturator foramen is oval and in males it is rounded.
 
The classification of ribs
 
True ribs are calls vertebrosternal and are pairs 1 - 7 they attach directly to the sternum via costal cartilages
False ribs are called vertebrochondral and are pairs 8 - 10 they attach to each others cartilage and then to the sternum via the cartilage of the 7th rib
Floating ribs or vertebral ribs are not attached to the sternum and are pairs 11 and 12

Bones for Lab Test
The Bones of the Cranium
  • Frontal: Forms the roof of the orbit, has the supraorbital foramen
  • Parietal:  Comes from "pared" meaning wall.  It froms the sides and roof of the cranium.  Articulates with its pair via the Sagittal suture, it articulates with the Frontal bone via the Coronal suture, it articulates with the Occipital bone via the Lambdoid suture, and to the Temporal bone via the Squamous suture.
  • Occipital:  Foramen magnum,  Hypoglossal canal, Occipital condyles (articulate with Atlas C1)
  • Temporal:  Named from the word time as it is located over the area people start to get grey hair.  The petrous portion is important because it contains the middle and inner ear.  Zygomatic process, Mandibular fossa, External auditory meatus, Styloid process, Mastoid process, Stylomastoid foramen, Jugular foramen, Internal acustic meatus, Carotid canal.
  • Ethmoid:  Crista galli, Cribriform plate, Superior and middle nasal conchae, Perpendicular plate of the ethmoid bone (froms the nasal septum together with the vomer bone)
  • Sphenoid:  Sella turcica (holds the "master gland", Optic canals, Superior orbital fissures, Foramen rotundum, Foramen ovale, Foramen spinosum,

Bones of the face

  • Mandible:  Mandibular condyles, Alveoli, Mental froamina
  • Maxilla:  Alveoli, Zygomatic processes, Palatine processes, Frontal processes, Incisive fossa, Inferior orbital fissure, Infraorbital foramen
  • Zygomatic
  • Nasal
  • Lacrimal:  Lacrimal fossa (duct)
  • Palatine
  • Vomer
  • Inferior nasal concha

Major Sutures

  • Coronal
  • Sagittal suture
  • Lambdoid suture
  • Squamous suture

Bones of the Orbit

  • Frontal
  • Zygomatic
  • Maxilla
  • Lacrimal
  • Ethmoid
  • Sphenoid
  • Palatine (the one most sutdents forget)

Foramen, Meatus, and Fissures

  • Supraorbital foramen - branch of the Trigeminal V nerve
  • Foramen magnum - Spinal cord exit and Accessory nerve XI enters
  • Hypoglossal canal - Hypoglossal nerve XII
  • Stylomastoid foramen - Facial nerve VII
  • Jugular foramen - Jugular vein and CN IX, X, and XI
  • Internal acoustic meatus - CN VII and VIII
  • Carotid canal - Internal carotid artery
  • Optic canals - CN II
  • Superior orbital fissures - CN III, IV, VI, and part of V
  • Foramen rotundum - part of V
  • Foramen ovale - part of V
  • Foramen spinosum - Middle meningeal artery
  • Olfactory foramen - CN I
  • Mandibular foramen - part of V
  • Mental foramen - Part of V
  • Inferior orbital fissure - part of V
  • Infraorbital foramen - Part of V
  • Lacrimal duct - drain tears into the nasal cavity
  • Incisive fossa
  • Greater palatine foramen

The Vertebral Column

  • 26 bones (started out as 33)
  • 4 curvatures - the cervical (secondary), Thoracic (primary), Lumbar (secondary), Sacral curvatures (primary)
  • 5 divisions ;
  • Cervical with 7 vertebrae (characteristics Transverse foramen) the first one is named Atlas after the god, the second is called the Axis and has the dens process.  The dens was at one time the body of the Atlas. 
  • Thoracic with 12 vertebrae (characteristic articular facets for the ribs).  
  • The Lumbar with 5 vertebrae. 
  • The Sacrum that is one bone made of 5 fused vertebrae. 
  • The Coccyx that is one bone made of 3 to 5 fused vertebrae.

Ribs

  • 12 pairs of ribs 24 total
  • First 7 pairs are TRUE RIBS because they are attached directly to hte sternum by individual costal cartilages
  • The next 3 pairs attach to the sternum indirectly and are called FALSE RIBS
  • The last 2 pairs are called the FLOATING RIBS because they have no anterior attachments to the sternum
  • Ribs have a head and a tubercle that articulate with the Thoracic vertebrae
  • The costal groove is on the inner and inferior face of the ribs and has nerves and blood vessels

Sturnum

  • The sturnum has 3 main parts the Manubrium, the Body, and the Xiphoid process
  • The Jugular notch, Sternal angle, and Xiphoid process are important landmarks

The Hyoid Bone is the only bone in the body that does not articulate with any other bone in the body.

Pectoral Girdle

  • Clavicle is a flat S shaped bone that has a sternal and acromial end
  • Scapulae are flat triangular bones.  Know the scapular spine, the Acromion process and the Glenoid cavity.  You can feel the Spine and the Acromion.  The Glenoid cavity recieves the head of the Humerus.

Humerus or Arm bone

  • Know the Head, Neck, Greater and lesser tubercles, Intertubercular groove, Deltoid tuberosity, Medial and lateral epicondyles, Trochlea, and Olecranon fossa.

Radius

  • Know the Head, Neck, Radial tuberosity and the Styloid process

Ulna

  • Know the Olecranon process, Trochlear notch, Styloid proces

Carpus

  • There are 8 carpals
  • The most frequently fractured one is the Scaphoid
  • The Pisiform is a Sesamoid bone

Metacarpals are 5 long bones that make up the palm of the hand

Phalanges are the finger bones.  Each phalange is a long bones.  Phalanges are in rows the Proximal, Middle and distal.  The first digit only has a proximal and distal row of phalanges.  Total phalanges 14 per hand.

The Pelvis

  • Sacrum
  • Ilium
  • Ischium
  • Ischial tuberosity - this is what you sit on
  • Pubis
  • Symphysis pubis - this is fibrocartilage
  • Pubic crest - point of attachment of the rectus abdominis muscle
  • Ischial spine - separates the greater and lesser sciatic notches
  • Greater sciatic notch - sciatic nerve goes through here
  • Lesser sciatic notch
  • Obturator foramen
  • Acetabulum - head of the femur fits in here
  • Sacral promontory
  • Terminaol line or pelvic brim - runs from the sacral promontory to the arcuate line to the pectin pubis and separates the False pelvis from the true pelvis.  Known as the pelvic inlet
  • Iliac crest - palpable because no muscles or tendons cross it
  • Anterior superior iliac spine

Lower extremity

  • Femur - know the Head, Neck (commonly fractured in women with osteoporosis), Greater trochanter (important landmark), Lesser trochanter, and the Medial and lateral epicondyle
  • Tibia - know the Tibial tuberosisty (point of attachment for the patellar ligament), Medial malleolus (May be pulled off in a sprained ankle)
  • Fibula - know the Lateral malleolus (may fracture when you sprain your ankle)

The medial and lateral malleolus form a notch for the Talus to fit.  The Talus is one of the tarsal bones

Bones of the Foot

Tarsals

  • There are 7 tarsal bones
  • The Talus articulates with the Tibia and Fibula as noted above
  • The Calcaneus is the Heel bone

Metatarsals are 5 long bones that make up the center of the foot

Phalanges same as in the hands.

 

Notes

The Skeleton

The Axial Skeleton

Eighty bones segregated into three regions

Skull

Vertebral column

Bony thorax

The Skull

The skull, the body’s most complex bony structure, is formed by the cranium and facial bones

Cranium – protects the brain and is the site of attachment for head and neck muscles

Facial bones

Supply the framework of the face, the sense organs, and the teeth

Provide openings for the passage of air and food

Anchor the facial muscles of expression

Anatomy of the Cranium

Eight cranial bones – two parietal, two temporal, frontal, occipital, sphenoid, and ethmoid

Cranial bones are thin and remarkably strong for their weight

Frontal Bone

Forms the anterior portion of the cranium

Articulates posteriorly with the parietal bones via the coronal suture

Major markings include the supraorbital margins, the anterior cranial fossa, and the frontal sinuses (internal and lateral to the glabella)

Skull: Anterior View

Skull: Posterior View

Parietal Bones and Major Associated Sutures

Form most of the superior and lateral aspects of the skull

Parietal Bones and Major Associated Sutures

Four sutures mark the articulations of the parietal bones

Coronal suture – articulation between parietal bones and frontal bone anteriorly

Sagittal suture – where right and left parietal bones meet superiorly

Lambdoid suture – where parietal bones meet the occipital bone posteriorly

Squamosal or squamous suture – where parietal and temporal bones meet

Occipital Bone and Its Major Markings

Forms most of skull’s posterior wall and base

Major markings include the posterior cranial fossa, foramen magnum, occipital condyles, and the hypoglossal canal

Occipital Bone and Its Major Markings

Temporal Bones

Form the inferolateral aspects of the skull and parts of the cranial floor

Divided into four major regions – squamous, tympanic, mastoid, and petrous

Major markings include the zygomatic, styloid, and mastoid processes, and the mandibular and middle cranial fossae

Major openings include the stylomastoid and jugular foramina, the external and internal auditory meatuses, and the carotid canal

Temporal Bones

Sphenoid Bone

Butterfly-shaped bone that spans the width of the middle cranial fossa

Forms the central wedge that articulates with all other cranial bones

Consists of a central body, greater wings, lesser wings, and pterygoid processes

Major markings: the sella turcica, hypophyseal fossa, and the pterygoid processes

Major openings include the foramina rotundum, ovale, and spinosum; the optic canals; and the superior orbital fissure

Sphenoid Bone

Ethmoid Bone

Most deep of the skull bones; lies between the sphenoid and nasal bones

Forms most of the bony area between the nasal cavity and the orbits

Major markings include the cribriform plate, crista galli, perpendicular plate, nasal conchae, and the ethmoid sinuses

Ethmoid Bone

Wormian Bones

Tiny irregularly shaped bones that appear within sutures

Facial Bones

Fourteen bones of which only the mandible and vomer are unpaired

The paired bones are the maxillae, zygomatics, nasals, lacrimals, palatines, and inferior conchae

Mandible and Its Markings

The mandible (lower jawbone) is the largest, strongest bone of the face

Its major markings include the coronoid process, mandibular condyle, the alveolar margin, and the mandibular and mental foramina

Mandible and Its Markings

Maxillary Bones

Medially fused bones that make up the upper jaw and the central portion of the facial skeleton

Facial keystone bones that articulate with all other facial bones except the mandible

Their major markings include palatine, frontal, and zygomatic processes, the alveolar margins, inferior orbital fissure, and the maxillary sinuses

Maxillary Bone

Zygomatic Bones

Irregularly shaped bones (cheekbones) that form the prominences of the cheeks and the inferolateral margins of the orbits

Other Facial Bones

Nasal bones – thin medially fused bones that form the bridge of the nose

Lacrimal bones – contribute to the medial walls of the orbit and contain a deep groove called the lacrimal fossa that houses the lacrimal sac

Palatine bones – two bone plates that form portions of the hard palate, the posterolateral walls of the nasal cavity, and a small part of the orbits

Other Facial Bones

Vomer – plow-shaped bone that forms part of the nasal septum

Inferior nasal conchae – paired, curved bones in the nasal cavity that form part of the lateral walls of the nasal cavity

Anterior Aspects of the Skull

Posterior Aspects of the Skull

External Lateral Aspects of the Skull

Midsagittal Lateral Aspects of the Skull

Inferior Portion of the Skull

Inferior Portion of the Skull

Orbits

Bony cavities in which the eyes are firmly encased and cushioned by fatty tissue

Formed by parts of seven bones – frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal, and ethmoid

Orbits

Nasal Cavity

Constructed of bone and hyaline cartilage

Roof – formed by the cribriform plate of the ethmoid

Lateral walls – formed by the superior and middle conchae of the ethmoid, the perpendicular plate of the palatine, and the inferior nasal conchae

Floor – formed by palatine process of the maxillae and palatine bone

Nasal Cavity

Nasal Cavity

Paranasal Sinuses

Mucosa-lined, air-filled sacs found in five skull bones – the frontal, sphenoid, ethmoid, and paired maxillary bones

Air enters the paranasal sinuses from the nasal cavity and mucus drains into the nasal cavity from the sinuses

Lighten the skull and enhance the resonance of the voice

Paranasal Sinuses

Hyoid Bone

Not actually part of the skull, but lies just inferior to the mandible in the anterior neck

Only bone of the body that does not articulate directly with another bone

Attachment point for neck muscles that raise and lower the larynx during swallowing
and speech

Vertebral Column

Formed from 26 irregular bones (vertebrae) connected in such a way that a flexible curved structure results

Cervical vertebrae – 7 bones of the neck

Thoracic vertebrae – 12 bones of the torso

Lumbar vertebrae – 5 bones of the lower back

Sacrum – bone inferior to the lumbar vertebrae that articulates with the hip bones

Vertebral Column

Vertebral Column: Curvatures

Posteriorly concave curvatures – cervical and lumbar

Posteriorly convex curvatures – thoracic and sacral

Abnormal spine curvatures include scoliosis (abnormal lateral curve), kyphosis (hunchback), and lordosis (swayback)

Vertebral Column: Ligaments

Anterior and posterior longitudinal ligaments – continuous bands down the front and back of the spine from the neck to the sacrum

Short ligaments connect adjoining vertebrae together

Vertebral Column: Ligaments

Vertebral Column: Intervertebral Discs

Cushionlike pad composed of two parts

Nucleus pulposus – inner gelatinous nucleus that gives the disc its elasticity and compressibility

Annulus fibrosus – surrounds the nucleus pulposus with a collar composed of collagen and fibrocartilage

Vertebral Column: Intervertebral Discs

General Structure of Vertebrae

Body or centrum – disc-shaped, weight-bearing region

Vertebral arch – composed of pedicles and laminae that, along with the centrum, enclose the vertebral foramen

Vertebral foramina – make up the vertebral canal through which the spinal cord passes

General Structure of Vertebrae

Spinous processes project posteriorly, and transverse processes project laterally

Superior and inferior articular processes – protrude superiorly and inferiorly from the pedicle-lamina junctions

Intervertebral foramina – lateral openings formed from notched areas on the superior and inferior borders of adjacent pedicles

General Structure of Vertebrae

Cervical Vertebrae

Seven vertebrae (C1-C7) are the smallest, lightest vertebrae

C3-C7 are distinguished with an oval body, short spinous processes, and large, triangular vertebral foramina

Each transverse process contains a transverse foramen

Cervical Vertebrae

Cervical Vertebrae: The Atlas (C1)

The atlas has no body and no spinous process

It consists of anterior and posterior arches, and two lateral masses

The superior surfaces of lateral masses articulate with the occipital condyles

Cervical Vertebrae: The Atlas (C1)

Cervical Vertebrae: The Axis (C2)

The axis has a body, spine, and vertebral arches as do other cervical vertebrae

Unique to the axis is the dens, or odontoid process, which projects superiorly from the body and is cradled in the anterior arch of the atlas

The dens is a pivot for the rotation of the atlas

Cervical Vertebrae: The Axis (C2)

Cervical Vertebrae: The Atlas (C2)

Thoracic Vertebrae

There are twelve vertebrae (T1-T12) all of which articulate with ribs

Major markings include two facets and two demifacets on the heart-shaped body, the circular vertebral foramen, transverse processes, and a long spinous process

The location of the articulate facets prevents flexion and extension, but allows rotation of this area of the spine

Thoracic Vertebrae

Lumbar Vertebrae

The five lumbar vertebrae (L1-L5) are located in the small of the back and have an enhanced weight-bearing function

They have short, thick pedicles and laminae, flat hatchet-shaped spinous processes, and a triangular-shaped vertebral foramen

Orientation of articular facets locks the lumbar vertebrae together to provide stability

Lumbar Vertebrae

Sacrum

Sacrum

Consists of five fused vertebrae (S1-S5), which shape the posterior wall of the pelvis

It articulates with L5 superiorly, and with the auricular surfaces of the hip bones

Major markings include the sacral promontory, transverse lines, alae, dorsal sacral foramina, sacral canal, and sacral hiatus

Coccyx

Coccyx (Tailbone)

The coccyx is made up of four (in some cases three to five) fused vertebrae that articulate superiorly with the sacrum

Sacrum and Coccyx: Anterior View

Sacrum and Coccyx: Posterior View

Bony Thorax (Thoracic Cage)

The thoracic cage is composed of the thoracic vertebrae dorsally, the ribs laterally, and the sternum and costal cartilages anteriorly

Functions

Forms a protective cage around the heart, lungs, and great blood vessels

Supports the shoulder girdles and upper limbs

Provides attachment for many neck, back, chest, and shoulder muscles

Uses intercostal muscles to lift and depress the thorax during breathing

Bony Thorax (Thoracic Cage)

Bony Thorax (Thoracic Cage)

Sternum (Breastbone)

A dagger-shaped, flat bone that lies in the anterior midline of the thorax

Results from the fusion of three bones – the superior manubrium, the body, and the inferior xiphoid process

Anatomical landmarks include the jugular (suprasternal) notch, the sternal angle, and the xiphisternal joint

Ribs

There are twelve pair of ribs forming the flaring sides of the thoracic cage

All ribs attach posteriorly to the thoracic vertebrae

The superior 7 pair (true, or vertebrosternal ribs) attach directly to the sternum via costal cartilages

Ribs 8-10 (false, or vertebrocondral ribs) attach indirectly to the sternum via costal cartilage

Ribs 11-12 (floating, or vertebral ribs) have no anterior attachment

Ribs

Structure of a Typical True Rib

Bowed, flat bone consisting of a head, neck, tubercle, and shaft

Appendicular Skeleton

The appendicular skeleton is made up of the bones of the limbs and their girdles

Pectoral girdles attach the upper limbs to the body trunk

Pelvic girdle secures the lower limbs

Pectoral Girdles (Shoulder Girdles)

The pectoral girdles consist of the anterior clavicles and the posterior scapulae

They attach the upper limbs to the axial skeleton in a manner that allows for maximum movement

They provide attachment points for muscles that move the upper limbs

Pectoral Girdles (Shoulder Girdles)

Clavicles (Collarbones)

The clavicles are slender, doubly curved long bones lying across the superior thorax

The acromial (lateral) end articulates with the scapula, and the sternal (medial) end articulates with the sternum

They provide attachment points for numerous muscles, and act as braces to hold the scapulae and arms out laterally away from the body

Clavicles (Collarbones)

Scapulae (Shoulder Blades)

The scapulae are triangular, flat bones lying on the dorsal surface of the rib cage, between the second and seventh ribs

Scapulae have three borders and three angles

Major markings include the suprascapular notch, the supraspinous and infraspinous fossae, the spine, the acromion, and the coracoid process

Scapulae (Shoulder Blades)

The Upper Limb

The upper limb consists of the arm (brachium), forearm (antebrachium), and hand (manus)

Thirty-seven bones form the skeletal framework of each upper limb

Arm

The humerus is the sole bone of the arm

It articulates with the scapula at the shoulder, and the radius and ulna at the elbow

Arm

Major markings

Proximal humerus includes the head, anatomical and surgical necks, greater and lesser tubercles, and the intertubercular groove

Distal humerus includes the capitulum, trochlea, medial and lateral epicondyles, and the coronoid and olecranon fossae

Medial portion includes the radial groove and the deltoid process

Humerus of the Arm

Forearm

The bones of the forearm are the radius and ulna

They articulate proximally with the humerus and distally with the wrist bones

They also articulate with each other proximally and distally at small radioulnar joints

Interosseous membrane connects the two bones along their entire length

Bones of the Forearm

Ulna

The ulna lies medially in the forearm and is slightly longer than the radius

Forms the major portion of the elbow joint with the humerus

Its major markings include the olecranon, coronoid process, trochlear notch, radial notch, and the styloid process

Radius

The radius lies opposite (lateral to) the ulna and is thin at its proximal end, widened distally

The superior surface of the head articulates with the capitulum of the humerus

Medially, the head articulates with the radial notch of the ulna

Major markings include the radial tuberosity, ulnar notch, and styloid process

Radius and Ulna

Hand

Skeleton of the hand contains wrist bones (carpals), bones of the palm (metacarpals), and bones of the fingers (phalanges)

Carpus (Wrist)

Consists of eight bones

Scaphoid, lunate, triquetral, and pisiform proximally

Trapezium, trapezoid, capitate, and hamate distally

Metacarpus (Palm)

Five numbered (1-5) metacarpal bones radiate from the wrist to form the palm

Their bases articulate with the carpals proximally, and with each other medially and laterally

Heads articulate with the phalanges

Phalanges (Fingers)

Each hand contains 14 miniature long bones called phalanges

Fingers (digits) are numbered 1-5, beginning with the thumb (pollex)

Each finger (except the thumb) has three phalanges – distal, middle, and proximal

The thumb has no middle phalanx

Hand

Pelvic Girdle (Hip)

The hip is formed by a pair of hip bones (os coxae, or coxal)

Together with the sacrum and the coccyx, these bones form the bony pelvis

The pelvis

Attaches the lower limbs to the axial skeleton with the strongest ligaments of the body

Transmits weight of the upper body to the lower limbs

Supports the visceral organs of the pelvis

Pelvic Girdle (Hip)

Ilium

The ilium is a large flaring bone that forms the superior region of the coxal bone

It consists of a body and a superior winglike portion called the ala

The broad posterolateral surface is called the gluteal surface

The auricular surface articulates with the sacrum (sacroiliac joint)

Major markings include the iliac crests, four spines, greater sciatic notch, iliac fossa, arcuate line, and the pelvic brim

Ilium: Lateral View

Ilium: Medial View

Ischium

The ischium forms the posteroinferior part of the hip bone

The thick body articulates with the ilium, and the thinner ramus articulates with the pubis

Major markings include the ischial spine, lesser sciatic notch, and the ischial tuberosity

Pubis

The pubic bone forms the anterior portion of the hip bone

It articulates with the ischium and the ilium

Major markings include superior and inferior rami, the pubic crest, pubic tubercle, pubic arch, pubic symphysis, and obturator foramen (along with ilium and ischium)

Pubis: Lateral View

Pubis: Medial View

Comparison of Male and Female Pelvic Structure

Female pelvis

Tilted forward, adapted for childbearing

True pelvis defines birth canal

Cavity of the true pelvis is broad, shallow, and has greater capacity

Comparison of Male and Female Pelvic Structure

Male pelvis

Tilted less forward

Adapted for support of heavier male build and stronger muscles

Cavity of true pelvis is narrow and deep

Comparison of Male and Female Pelvic Structure

Comparison of Male and Female Pelvic Structure

The Lower Limb

The three segments of the lower limb are the thigh, leg, and foot

They carry the weight of the erect body, and are subjected to exceptional forces when one jumps or runs

Femur

The sole bone of the thigh is the femur, the largest and strongest bone in the body

It articulates proximally with the hip and distally with the tibia and fibula

Major markings include the head, fovea capitis, greater and lesser trochanters, gluteal tuberosity, lateral and medial condyles and epicondyles, linea aspera, patellar surface, and the intercondylar notch

Femur

Leg

The tibia and fibula form the skeleton of the leg

They are connected to each other by the interosseous membrane

They articulate with the femur proximally and with the ankle bones distally

They also articulate with each other via the immovable tibiofibular joints

Tibia

Receives the weight of the body from the femur and transmits it to the foot

Major markings include medial and lateral condyles, intercondylar eminence, the tibial tuberosity, anterior crest, medial malleolus, and fibular notch

Tibia and Fibula

Fibula

Sticklike bone with slightly expanded ends located laterally to the tibia

Major markings include the head and lateral malleolus

Foot

The skeleton of the foot includes the tarsus, metatarsus, and the phalanges (toes)

The foot supports body weight and acts as a lever to propel the body forward in walking and running

Tarsus

Composed of seven bones that form the posterior half of the foot

Body weight is carried primarily on the talus and calcaneus

Talus articulates with the tibia and fibula superiorly, and the calcaneus inferiorly

Other tarsus bones include the cuboid and navicular, and the medial, intermediate, and lateral cuneiforms

Tarsus

Calcaneus

Forms the heel of the foot

Carries the talus on its superior surface

Point of attachment for the calcaneal (Achilles) tendon of the calf muscles

Metatarsus and Phalanges

Metatarsals

Five (1-5) long bones that articulate with the proximal phalanges

The enlarged head of metatarsal 1 forms the "ball of the foot"

Phalanges

The 14 bones of the toes

Each digit has three phalanges except the hallux, which has no middle phalanx

Metatarsus and Phalanges

Arches of the Foot

The foot has three arches maintained by interlocking foot bones and strong ligaments

Arches allow the foot to hold up weight

The arches are:

Lateral longitudinal – cuboid is keystone of this arch

Medial longitudinal – talus is keystone of this arch

Transverse – runs obliquely from one side of the foot to the other

Arches of the Foot

Developmental Aspects: Fetal Skull

Infant skull has more bones than the adult skull

At birth, fetal skull bones are incomplete and connected by fontanels

Fontanels

Unossified remnants of fibrous membranes between fetal skull bones

The four fontanels are anterior, posterior, mastoid, and sphenoid

Developmental Aspects: Fetal Skull

Skull bones such as the mandible and maxilla are unfused

Developmental Aspects: Growth Rates

At birth, the cranium is huge relative to the face

Mandible and maxilla are foreshortened but lengthen with age

The arms and legs grow at a faster rate than the head and trunk, leading to adult proportions

Developmental Aspects: Spinal Curvature

Only thoracic and sacral curvatures are present at birth

The primary curvatures are convex posteriorly, causing the infant spine to arch like a four-legged animal

Secondary curvatures – cervical and lumbar – are convex anteriorly and are associated with the child’s development

Developmental Aspects: Old Age

Intervertebral discs become thin, less hydrated, and less elastic

Risk of disc herniation increases

Loss of stature by several centimeters is common after age 55

Costal cartilages ossify causing the thorax to become rigid

All bones lose mass