Download Essentials of Human Anatomy The Skeletal System 1

Essentials of Human Anatomy
The Skeletal System 1
Bone
• Bones are organs
• Bones are composed of all tissue types.
• Their primary component is osseous
connective tissue.
• The matrix is sturdy and rigid due to
calcification (also called mineralization).
Function of Bones
• Support: form the framework that supports the body
and cradles soft organs
• Protection: provide a protective case for the brain,
spinal cord, and vital organs
• Movement: provide levers for muscles
• Mineral storage: reservoir for minerals, especially
calcium and phosphorus
• Blood cell formation: hematopoiesis occurs within the
marrow cavities of bones
• Energy storage (fat in yellow marrow)
Support and Protection
• Bones provide structural support and serve as
a framework for the entire body.
• Bones protect many delicate tissues and
organs from injury and trauma.
Movement
• Muscles attach to the bones of the
skeleton
–Contract and pull on bone
–Functions as a series of levers.
Storage of Mineral and Energy Reserves
• More than 90% of the body’s
reserves of the minerals calcium and
phosphate are stored and released
by bone.
Hematopoiesis
Blood Cell Formation
• Blood cell production in red bone marrow
– located in some spongy bone.
• Red bone marrow contains stem cells
– form all of the blood cell types.
Changes in the Human Skeleton
•
In embryos, the skeleton is primarily hyaline
cartilage
•
During development, much of this cartilage
is replaced by bone
•
Cartilage remains in isolated areas
 Bridge
 Parts
of the nose
of ribs
 Joints
Classification of Bones on the Basis of
Shape
Classification of Bones

Long bones
•
Generally longer than
wide.
•
Have a shaft with
heads at both ends.
•
Contain mostly
compact bone
•
Examples: Femur,
humerus
Classification of Bones

Short bones
•
Generally cube-shape
•
Contain more spongy
bone than compact
•
Examples: Carpals,
tarsals
Classification of Bones

Flat bones
•
Thin and flattened like
pancackes.
•
Usually curved
•
They have two thin layers
of compact bone
sandwiching a layer of
spongy bone
•
Examples: Skull, ribs,
sternum
Classification of Bones

Irregular bones
•
Do not fit into other
bone classification
categories
•
Irregular shape
•
Example: Vertebrae
The Histologic Types:
•
Compact bone ( cortical)
•
Spongy bone ( cancellous)
Compact Bone:
• Haversian system, or osteon – the structural unit
of compact bone
– Lamella – weight-bearing, column-like matrix tubes
composed mainly of collagen
– Haversian, or central canal – central channel
containing blood vessels and nerves
– Volkmann’s canals – channels lying at right angles to
the central canal, connecting blood and nerve supply
of the periosteum to that of the Haversian canal
Compact Bone
• Osteocytes – mature bone cells
• Lacunae – small cavities in bone that contain
osteocytes
• Canaliculi – hairlike canals that connect
lacunae to each other and the central canal
Compact Bone:
Spongy (cancellous) Bone
• Does not contain osteons.
• trabeculae surrounding red marrow spaces
Cell Types of Bone
3 types of cells in bone tissue
• Osteoblasts:
– Form matrix & collagen fibers but can’t divide
• Osteocytes:
– Mature cells that no longer secrete matrix
• Osteoclasts:
– Huge cells from fused monocytes (WBC)
– Function in bone resorption at surfaces such as
endosteum
SKLETAL SYSTEM
• It is divided into two parts :
Axial
Appendicular
Bone Structure - External
 Cartilage
protection for
joints
Bone Structure - External
Epiphyses
Expanded ends of long bones
Exterior is compact bone, and
the interior is spongy bone
Epiphyse
Joint surface is covered with
articular (hyaline) cartilage
location of red bone marrow
Epiphyseal line separates the
diaphysis from the epiphyses
Bone Structure - External
Diaphysis
Tubular shaft that forms
the axis of long bones
Composed of compact
bone that surrounds the
medullary cavity
Yellow bone marrow
(fat) is contained in the
medullary cavity
Diaphysis
Bone Membranes
• Periosteum – double-layered protective
membrane
– Outer fibrous layer
• dense regular connective tissue
– Inner osteogenic layer
• composed of osteoblasts and osteoclasts
• Richly supplied with nerve fibers, blood, and lymphatic
vessels, which enter the bone via nutrient foramina
• Secured to underlying bone by Sharpey’s fibers
• Endosteum – delicate membrane covering
internal surfaces of bone
Blood and Nerve Supply of Bone
• Periosteal arteries
– Supply periosteum
• Nutrient arteries
– Enter through nutrient foramen
– Supplies compact bone of diaphysis &
red marrow
• Metaphyseal & epiphyseal aa
– Supply red marrow & bone tissue of
epiphyses
Skeletal system includes
Axial division
– Skull and associated bones
Auditory ossicles
Hyoid bones
– Vertebral column
– Thorax (Thoracic cage )
– Ribs sternum

Appendicular division
- Pectoral girdle
- Pelvic girdle
The Adult Skull

skull is formed of two sets of bones:-

cranium is encloses and protects the fragile brain
tissues.
= 8 bones: frontal, occipital, 2 temporals, 2
parietals, sphenoid and ethmoid

facial bones holed the eyes in an anterior position
and allow the facial muscles to show our feelings.
= 14 bones: nasals, maxillae, zygomatics,
mandible, lacrimals, palatines, inferior nasal
conchae, vomer.
Bones of the Cranium
Frontal View
Frontal
Frontal View
Parietal
Frontal View
Temporal
Frontal View
Nasal
Frontal View
Vomer
Frontal View
Zygoma
Frontal View
Maxilla
Frontal View
Mandible
Frontal View
Frontal
Parietal
Temporal
Nasal
Vomer
Zygoma
Maxilla
Mandible
Frontal View
Lateral View
Frontal
Lateral View
Parietal
Lateral View
Temporal
Lateral View
Nasal
Lateral View
Zygoma
Lateral View
Maxilla
Lateral View
Mandible
Lateral View
Sphenoid
Lateral View
Occipital
Lateral View
Mastoid Process
Lateral View
External Auditory Meatus
Lateral View
Parietal
Frontal
Sphenoid
Temporal
Occipital
Mastoid Process
Nasal
Zygoma
Maxilla
Mandible
External Auditory Meatus
Lateral View
Fetal skull
• The skull of a newborn differs from an adult one:
–
–
–
–
–
–
The infant’s face is very tiny compared to the cranium.
The whole skull is large compared to infant’s body length
The adult skull represents only 1/8th of the total body
length, whereas that of new born infant is 1/4th as
long as its entire body.
The fetal skull has fibrous cartilage area between the
cranial bones.
These membranous area are called fontanels, which
allow the fetal skull to be compressed during birth
and allow the infant’s brain to be grow.
The fontanels usually closes by age 20-22 months.
Fetal skull
Adult Vertebral Column
Formed from 33 bones in the adult
 Divided into five major regions
 Cervical vertebrae
7 vertebrae of the neck region
 Thoracic vertebrae
12 vertebrae of the thoracic region
 Lumbar vertebrae
5 vertebrae of the lower back
 Sacrum
Inferior to lumbar vertebrae
Articulates with coxal bones
 Coccyx
Most inferior region of the vertebral column
Intervertebral disks
The single vertebrae are separated
by pads of elastic cartilage
intervertebral disks
Cushion vertebrae and absorb
shocks.
 Have a high water content (about
90%) and are compressible.

General Structure of Vertebrae
Cervical Vertebrae
• Atlas – 1st; supports
head
• Axis – 2nd; dens pivots
to turn head
• transverse foramina
• bifid spinous
processes
• vertebral prominens –
useful landmark
Thoracic Vertebrae
long spinous processes
Rib facets
Lumbar Vertebrae
 large bodies
 thick, short
spinous
processes
Sacrum
 five fused vertebrae
 median sacral crest
 posterior sacral
foramina
 posterior wall of
pelvic cavity
 sacral promontory
Coccyx
Tailbone
Four fused vertebrae
Thorax
Often called the thoracic cage.
Components of the thorax
Sternum– anteriorly
 Ribs – laterally
 Thoracic vertebrae – posteriorly

Protects thoracic organs (heart, lungs, and
major blood vessels).
The Thorax
Sternum
Breast bone is typical flat bone and the result
of fusion of three bones.
Manubrium – superior section
 Body – bulk of sternum
 Xiphoid process – inferior end of sternum

Attached to the 1st seven pairs of ribs.
Ribs
The 12 pairs of ribs form the wall of the
thoracic cage.
All ribs attach to vertebral column posteriorly
True ribs - superior seven pairs of ribs Attach
directly to sternum by costal cartilage
False ribs – inferior five pairs of ribs
Have cartilages attachment to the sternum that
are indirect or are not attached at all.
Ribs 11–12 are known as floating ribs

The Thoracic cage
Ribs
Ribs
APPENDICULAR SKELETON
• It is formed of :
Pectoral girdle
Pelvic girdle
Bones of the upper and lower limbs.
PECTORAL GIRDLE
• It is formed of :
• CLAVICLE which holds
the arm away from the
thorax.
• SCAPULA (WING).
Clavical
Scapula
UPPER LIMB
• ARM :Humerus
• FORE ARM: Radius &
Ulna.
• Long bones They are
formed of Epiphysis on
each end. Diaphysis a
tubular shaft. It is
covered externally by
the periosteum.
HAND
• WRIST : Carpal bones.
• PALM : Metacarpal
bones.
• FINGERS : Phalanges.
• They are examples of
short bones.
PELVIC GIRDLE
• Formed of the two HIP
bones.
• Each hip bone is formed
of three parts :
 ILium.
 Ischium.
 Pubis.
• The hip bones and the
sacrum form the bony
pelvis.
LOWER LIMB
• THIGH : Femur.
• LEG : Tibia & Fibula.
• Also Patella bone
FOOT
• TARSUS : Tarsal bones.
• Metatarsals.
• Phalanges.