Anatomy Exam 2 - Mizzou

Functions of the Skeletal System (5)

Support: entire body

Protection: Viscera (organs)

Movement: Attachment for the muscles

Hemopoiesis: Blood cell production

Energy & Mineral Reserves: bones have calcium

Are bones organs?

Yes - bones consist of various types of tissue -- Including blood

Is the skeleton internal or external?

Internal

Where do bones meet?

At joints

Skeleton consist of

Bones, cartilages, joints, and ligaments

How many named bones are there?

206

Skeleton subdivides into what?

Axial & appendicular

Axial Skeleton includes

Includes: Skull, vertebral, column, thoracic cage(sternum and ribs)

Appendicular Skeleton includes

Includes: pectoral girdle, upper limb, pelvic gridle, lower limbs

Axial & Appendicular Skeleton

Axial Skeleton amount of bones

80 named bones

Axial Skeleton Functions

Supports head, neck, and trunk

Axial Skeleton protects..

protects brain, spinal cord, thoracic organs

Bone Markings

characteristics on the surface of the axial and appendicular bones that indicate attachments, articulations or openings for nerves and blood vessels, explains Boundless.

Examples: Foramen, fossa, process, meatus, canal

Foramen (foramina) & example

a hole in a bone (typically for nerves or blood vessels)

Examples: foramen magnum, infraorbital foramen)

Fossa (fossae) & example

a depression in a bone

Examples: mandibular fossa, lacrimal fossa

Process & examples

projection from bone, narrow or wide, protrudes from surrounding bone

ex.: styloid or mastoid process

Meatus & examples

a hole or tube-like structure

(e.g. auditory meatus)

Canal & examples

a groove or tube-like structure

(e.g. optic canal)

Cartilage Tissue Structure

Avascular (no blood supply)

Cell Type: chondrocytes (in lacunae)

Cartilage Functions

Support soft tissues

Model for formation of bone

Gliding surface at articulations

Three types of cartilage

Hyaline, elastic, fibrocartilage

Hyaline Cartilage

most common kind of cartilage. Has tiny nearly invisible collagen fibers called fibrils

Fibrils

Tiny nearly invisible collagen fibers

Hyaline Cartilage functions

ends of long bones, costal cartilages, respiratory structures, fetal skeleton

Elastic Cartilage

Similar to hyaline but lots of elastic fibers. Very resilient and flexible, tolerates repeated bending

Elastic Cartilage is found where?

in pinna (outer ear) and epiglottis

Fibrocartilage

has little ground substance & matrix has thick, dense collagen fibers.

Resists strong compression

Fibrocartilage is found where?

in inter-vertebral disks, knee joint, public symphysis

Cartilage Locations

Bone Tissue

Much denser than cartilage, very little fluid. Resists compression and tension; very strong. Well vascularized, so it heals/remodels easy. Made of organic and inorganic materials

Osteoblasts & Osteoclasts

Bone is constantly being built up or broken down - growth, strengthening, remodeling, healing, maintenance.

Osteoblasts

Builds new bone

Osteoclasts

Break down (consume) bones and are mature bone cells

Spongy Bone

(Trabecular bone)

Inside bones

Better at shock absoption

Compact Bone

(Cortical)

Smooth, dense, external portion of bones

Strong, rigid

Compact Bone Structure

Osteon - structure unit

Osteon

-Made up of concentric tubes are called lamellae

-Oriented parallel to the long axis and main compression stresses

- Haversian (central) canal

Lamellae

what makes up osteon

Haversian (central) canal

runs through core of each osteon & provides blood supply, nutrients, nerves

Bones shapes and sizes

Long bone - humerus

Short bone - talus

Flat bone - sternum

Irregular bone - vertebra

Structure of a Long Bone 1

Epiphysis - ends

Epiphyseal Line - growth plate

Diaphysis - shaft

Compact bone - superficial

Spongy bone - deep

STRUCTURE OF LONG BONE 1

Structure of a Long Bone 2

Periosteum - sheath on outside of bone

Endosteum - lines internal cavity

Medullary Cavity - Bone marrow

Nutrient Arteries - Feed bone

Articular cartilage is on ends

Flat, Irregular, and Short Bones

-Compact bone with periosteum on outside

-Spongy bone with endosteum inside

-Contain marrow but don't have a marrow cavity

Bone Development & Growth

-Osteogenesis/Ossification

-Being in the embryo & continues through life (more slowly in the adult)

-Before week 8, skeleton made of hayaline cartilage or mesenchyme

-Before week 8, bone tissue begins to replace most cartilage & mesenchyme

-Ossification may be endochondral or intramembranous

Osteogenesis/Ossification

Process of bone formation

-May be endochondral or intramembranous

Intramembranous Ossification

-Bone grows within a membrane

-Forms many flat bones (bones of the skull) as well as maxillae, zygomatic, mandible & center of calvicle

Two types of Ossification

- Intramembranous Ossification

- Endochondral Bone Ossification

Endochondral Bone Ossification

-Most of the bones of the skeleton form this way

1) Skeleton begins as Hyaline Cartilage model

2) Bone replaces cartilage

3) Epiphyseal (growth) plates ossify eventually

Closure of the Epiphyseal Plates

Cartilage is gradually replaced by bone tissue on both sides of the epiphyseal plate (primary center of ossification at diaphysis & secondary centers of ossification in epiphyses)

-When centers of ossification meets (a epiphyseal plate), growth stops

Skull

- 28 Bones - very complex

- Most are "flat" bones, formed via intramembranous ossification

- united by sutures (interlocking, immovable joints)

Major Structures of Skull

- Coronal Structure

- Squamous suture

- Lambdoid suture

- Sagittal Suture

- Parietal bone

- Frontal bone

- Temporal bone

- Occipital bone

- Sphenoid bone

- Ethmoid bone

Fetal/Infant Skull & Structures

- Connected by flexible connective tissues to allow head to deform during birth & allow rapid brain growth

- Areas between bones are called fontanelles (soft spots) & fuses over times

Craniosynostosis

pre-mature fusion of skull bones, leads to unusual cranial vault shape

The Skull

Subdivides into cranial & facial divisions

Cranial bone functions

Protect brain

provides attachments sites for some head/neck muscles

Facial bone functions

form the framework of face

opening the passage of air & food

Hold the teeth

anchor muscles of face

Cranium

Can be subdivided into vault (calvarium) & base

Vault = superior, lateral & posterior bones of skull (includes forehead)

Base = inferior part of cranium

Cranium is made up of ...

8 Bones

- Frontal (forehead)

- Occipital

- Sphenoid

- Ethmoid

- 2 Parientals (left & right)

- 2 Temporals (left & right)

Pariental Bones

Made up most of superior part of skull, extend posteriorly & laterally

**Note: Sagittal suture (between two pariental bones), lambdoid surure (between pariental & occipital bones)

Occipital Bone

Posterior part of cranium & cranial base

Foramen magnum = large opening in occipital bone that allows the spinal cord to pass & connect the brain

Occupital condyles are region where the skull articulates with vertevral column (atlas or C1 vertebra)

Temporal Bones

Paired temporal bones (left and right sides) house opening to ear, forms the base of cheekbone.

3 main regions: petrous, tympanic and squamous.

Temporal Bones Regions

Petrous is best seen internally, contains middle and inner ear cavities. Petrous=hard.

The external acoustic meatus (EAM): opening in the tympanic region leading to the middle & inner ear

Squamous portion is the vertical portion (part of cranial vault).

Temporomandibular Joint (jaw joint)

The condyle of the mandible articulates with temporal bone at the mandibular fossa.

Middle Ear Cavity (inside temporal bone)

3 ear ossicles in the middle ear: malleus, incus and stapes. Bones are really small.

Sound waves cause vibrations of these bones that are transmitted to the inner ear (cochlea).

Sphenoid

Large and wing-shaped.

Landmark: Sella turcica - bony depression that holds the pituitary gland.

Sphenoid is the only cranial bone that articulates with every other cranial bone.

Ethmoid Bone

Just anterior to the sphenoid is the ethmoid bone.

Ethmoid takes up most of the area between the nasal cavity and the orbits.

Forms some boundaries of the nasal cavity, also separates nasal cavity from the brain.

Ethmoid

- Crista galli attaches to cribriform plate; separates nasal cavity from brain, site of attachment for dura mater (membrane covering brain)

- Cribriform plate helps form the roof of nasal cavities; foramina allow passage of olfactory nerves into brain.

Facial Skeleton

14 Bones of the Face

Mandible (unpaired)

Vomer (unpaired)

2 Nasals

2 Lacrimals

2 Maxillae

2 Zygomatics

2 Palatine bones

2 Inferior nasal conchae

Bones of the Facial Skeleton

Lacrimal bones (paired):

Lacrimal groove allows tears to drain into nasal cavity

Inferior nasal concha

(paired)

Vomer

(unpaired)

Nasal bones (paired)

form bridge of nose

attach to cartilages

that form nose.

Zygomatic bones

(paired) form

cheekbones

Maxillae

(paired)

Mandible

(unpaired

Maxilla(e)

Maxillary bones form upper jaw (paired, left & right).

Articulate with all other facial bones except mandible.

Alveolar processes contains teeth.

Frontal processes extend upward to reach frontal bone

Zygomatic processes of maxilla articulate with zygomatic bone

Orbit

Supports the eyes & muscles that move the eyes. Orbit also contains fat and lacrimal glands (tear producing glands).

Walls formed by frontal, sphenoid, zygomatic, maxillary, palatine, lacrimal & ethmoid bones.

Nasal Cavity in Sagittal Section

Lateral walls of nasal cavity: nasal bones, nasal conchae (superior, middle, inferior), maxillae, palatines.

Floor of nasal cavity = hard palate. Formed by palatine process of maxillae, horizontal plate of palatine.

Palate & Inferior Nasal Septum

Hard palate is composed of maxillary bones and the palatine bone.

Vomer forms inferior portion of nasal septum.

Cleft Palate

Failure of the 2 sides of the palate to join during development leads to cleft palate. Severity varies.

Opening between mouth and nasal cavity makes effective nursing difficult.

Can be repaired surgically with good outcomes.

Mandible

Largest, strongest bone in the face.

Body of mandible contains lower teeth.

Tooth sockets are on the superior border (=alveolar processes)

Mandibular symphysis (not visible) is where the two halves of the body join to form the chin (=mental protuberance).

Vessels & nerves enter via mandibular foramen & exit via mental foramen inferior to teeth

Condyle articulates with the temporal bone to form the temporomandibular joint (TMJ; both sides of jaw).

Coronoid process serves as an attachment site for the temporalis muscle, a major chewing muscle.

Fetal/Infant Face

Cranium is proportionately huge relative to the face in infancy & early childhood.

By age 2, skull is 3/4 adult size.

Between ages 6-13, face grows outward & develops more "adult" proportions; body size begins to catch up with head.

Hyoid

"Free floating" bone in neck inferior to mandible.

Only bone in skeleton that does not articulate with any other bone.

Acts as base for tongue, site of muscle attachments for muscles that move the larynx.

Thoracic Cage

Includes thoracic vertebrae, ribs, sternum and costal cartilages.

Protects heart, lungs, other organs.

Supports pectoral girdle and provides attachment points.

Intercostal spaces hold muscles that aid in breathing.

Sternum

3 bones

-- Manubrium

-- Body

-- Xiphoid Process

Articulates with:

-- Clavicles

-- Ribs & costal cartilages

Sternal angle is important landmark for thoracic anatomy.

Rib Cage

Function: protect internal organs, aid in respiration.

12 pairs of ribs.

All ribs attached posteriorly to thoracic vertebrae

1st 7 attach to sternum by costal cartilages (true ribs).

8-10 are false ribs - do not have a direct attachment to the sternum. They attach via a shared costal cartilage.

11 and 12 are "floating ribs" - they do not attach anteriorly to the sternum.

Rib Structure

Main part of rib is the shaft (body).

Rib articulates with the vertebra at the head and tubercle

"Neck" (not labeled) is a thinner region between the head and tubercle. Head has 2 "facets" - one facet articulates with the body of "its" vertebra; one articulates on the body of the vertebra superior to it.

Tubercle articulates with a facet on the transverse process of the vertebrae.

Vertebral Column

26 vertebrae

-- 7 Cervical

-- 12 Thoracic

-- 5 Lumbar

-- 5 Sacral (will fuse into 1)

-- 4 Coccyx (will fuse into 1)

Functions:

-- Protect spinal cord

-- Supports body axis

-- Attachment points for ribs & muscles of neck & back.

-- Anchor pectoral & pelvic girdles

Curves of the Spine

Vertebrae become larger as move inferiorly to support weight

Sacrum articulates with hip bones of pelvis, passes weight to appendicular skeleton.

Curves increase flexibility; also position center of gravity over axis of body

Curves of the Spine: Scoliosis

Scoliosis - lateral curvature of the spine.

Usually treated with body braces or surgery when young

Lateral curvature is abnormal!!.

Kryphosis (Dowager's Hump)

Excessive curvature of the thoracic spine.

Typically the result of vertebral body factures caused by osteoporosis.

Osteoporosis

Results from imbalance in normal bone building & degradation cycle. Particularly after menopause, women don't absorb as much calcium & so osteoclasts break bone down to release the calcium into the bloodstream.

Lordosis

Lordosis is excessive curvature of the lumbar spine.

Usually temporary & resulting from shift for a larger front load (belly in men, pregnant women).

Basic Vertebral Anatomy

Body is located anteriorly.

Vertebral arch made of lamina & pedicles

-- Creates vertebral foramen

---- Surrounds spinal cord

Stacked vertebrae result in vertebral canal.

-- Spinous processes and transverse process are ligament & muscle attachment sites

Vertebrae articulate at superior and inferior articular processes and facets

-- Each articular process has an articular facet.

-- Individual vertebrae articulate with the vertebrae just superior and inferior to it.

-- This articulation also makes intervertebral foramina between two vertebrae.

Vertebral Column & Spinal Cord

Notice how the spinal cord passes through, & is protected within, the vertebral (spinal) canal.

Spinal nerves exit between the body of the vertebra & the vertebral arch via intervertebral foramina

Seven Cervical Vertebrae (C1-C7)

Cervical vertebrae features:

-- Have transverse foramina

-- Articular facets face superior/inferior

-- Bifid (split) spinous processes

Atlas (C1) and Axis (C2) are unusual (see the next slides

Atlas (C1)

Atlas does not have a body or a spinous process.

Articulates with occipital condyles, allows flexion/extension of

head (nodding "yes").

Axis (C2)

Dens articulates with atlas, allows rotational movement (shaking head "no"). Dens used to be the body of the atlas, but not part of axis.

Twelve Thoracic Vertebrae (T1-T12)

Thoracic vertebrae:

Costal facets for ribs, located on each body of the thoracic vertebrae.

Articular facets face anterior/posterior

Spinous processes are long and project inferiorly

Five Lumbar Vertebrae (L1-L5)

Lumbar vertebrae:

-- Large bodies

-- Articular facets face medial/lateral

-- Short, flat spinous processes

Sacrum & Coccyx

Sacrum

-- 5 Fused Vertebrae

-- Forms posterior wall of pelvis.

-- Ala on lateral sacrum articulate with hip bones to form sacroiliac joints.

Coccyx

-- 3-5 fused vertebrae

-- "Tail bones"

Appendicular Skeleton

Pectoral Gridle & Uppper Limb

Pectoral Girdle, Arm, forearm, hand

Pectoral Girdle: Clavicles & Scapulae

Includes the left and right scapulae & left & right clavicles.

Note that the scapulae do NOT join to the axial skeleton at all, and their articulation with the clavicle is very loose.

Attached to the axial skeleton by way of associated muscles & ligaments.

Provides a highly flexible system (lots of movement allowed), but not very stable.