The Skeletal System

Question 1

Functions of the skeleton: The skeleton performs several critical functions [5]

Answer 1

• Provides the structural frame for the body
• provides the lever system for movement with the muscles
• provides protection for the vital and internal organs
• acts as a storage site for minerals, particularly calcium
• acts as a production site for blood cells within the bone marrow

Question 2

The functions of the skeleton: The cycle of bone growth in dogs is similar to _______

Answer 2

Humans

Question 3

The functions of the skeleton: Growth plates exist at the ends of long ____

Answer 3

Bones

Question 4

The functions of the skeleton: The bones of the skull and pelvis gradually fuse to a nearly _________ relationship in the adult

Answer 4

Immobile

Question 5

The functions of the skeleton: There are tiny movements along the suture lines of the cranial-sacral system that can have immense impact on the _______ ____ & ________ ________ of the dog and cat.

Answer 5

Hydrostatic flow & nervous function

Question 6

Elements of the S.S. [7]

Answer 6

• Axial skeleton
• Appendicular skeleton
• Clavicle
• Spinous Processes (SPs)
• Transverse Processes (TVPs)
• Atlas (C1)
• Axis (C2)

Question 7

Elements of the S.S.:

Axial Skeleton

Answer 7

Refers to the bones located along the midline or in the core of the body

Question 8

Elements of the S.S.:

Appendicular Skeleton

Answer 8

• refers to the bones of the limbs
• the forelimb and hind-limb are part of the appendicular skeleton
• the sacroiliac joint is the only joint that connects the Appendicular skeleton to the Axial skeleton.
• the forelimb is connected to the axial skeleton through soft tissue structures only

Question 9

Elements of the S.S.:

Clavicle

Answer 9

• Technically doesn’t exist in dogs, present in some breeds
• when a vestigial clavicle is present, it is very small and embedded within a tendon
• for the purpose of our study, we don’t recognize clavicles. It is difficult / impossible to palpate and doesn’t reflect in the health of the musculoskeletal system.

Question 10

Elements of the S.S.:

Spinous Processes (SPs) and Transverse Processes (TVPs)

Answer 10

• There are processes located on the vertebrae of the spinal column
• Muscles are attached to these processes, so it’s particularly important to be familiar with these processes
• notice that both the SPs and TVPs of the cervical vertebrae are short and broad
• the thoratic vertebrae have long SPs and much shorter TVPs near the articulation with the ribs
• the lumbar vertebrae have very long and broad TVPs for muscle attachment and to limit movement in the low back
• also noticed that the SPs of the spine have either a caudal tilt (in the thoracic spine) for a cranial tilt (in the lumbar spine)
• the SPs of the 10th thoracic vertebrae (T10) doesn’t have a tilt and is called the point of aclination (a = without, clin = incline).

Question 11

Elements of the S.S.:

Atlas (C1) and Axis (C2)

Answer 11

• know the special relationship that exists between the first cervical vertebra (Atlas) and the second cervical vertebrae (Axis)
• The joint in the neck is responsible for rotation of the head and upper neck and is called the atlantoaxial joint.

Question 12

Atlantoaxial joint

Answer 12

The joint in the neck is responsible for rotation of the head and upper neck

Question 13

Elements of the Axial System:

Skull

Answer 13

• The dog skull is composed of the maxillary bones (upper jaw), the mandibular bones (lower jaw), and a number of pained (left & right) plates (frontal, parietal, occipital, zygomatic, lacrimal, palatine, nasal, incisive, and temporal).
• These bones are joined by tight suture lines, thus creating the appearance of a singular bony structure.
• Faulty alignment of the suture lines between bones can create imbalance & sinus dysfunction. Dogs, like humans, can experience tension & swelling at the temporomandibular joint. This joint occurs at the junction of the temporal & mandibular bones.

Question 14

Elements of the Axial System:

Cervical Vertebrae (7)

Answer 14

• All mammals have 7 cervical vertebrae
• The atlas forms a joint with the skull at the location of the occipital bones called the atlanto-occipital joint.
• The first 2 cervical vert. are specialized in their shape and function and are named the atlas (C1) and axis (C2)
• The first two vertebrae form a second joint called the atlantoaxial joint where the majority of the rotation of the head and neck occurs.
• The remaining cervical joints are collectively called intervertebral joints and can be distinguished by the number of the vertebrae (i.e. the intervertebral joint of C4 - C5). (A trick for remembering that C1 is the atlas is that it holds up the skull, just as the Greek hero Atlas holds the earth on his shoulders.)

Question 15

Elements of the Axial System:

Thoracic Vertebrae (13)

Answer 15

• The thoracic vertebrae are similar in structure to the human.
• The dog has 13 thoracic vertebrae and 13 pair of corresponding ribs attaching to the thoracic vertebra.
• The thoracic vertebrae have a straight alignment as compared to the human kyphotic curve (rearward curvature).
• Thoracic vertebrae mark the first appearance of a prominent spinous process (SPs). The spinous processes form an arc at the shoulder that defines the withers. -These processes serve as an attachment site for several muscles.
• The SPs at T1-T9 have a caudal tilt (toward the tail). The SPs of T11, T12, and T13 have a cranial (toward the head) tilt, while the SPs of T10 is upright or without incline.
• This unique area is called the point of aclination and can be a significant point of stress for dogs with back issues. —Any displacement of these SPs can create a locked back (impaired movement) and pain.
• A common site of subluxation (misalignment) occurs at C7-T1 and at T13 and the first lumbar vertebrae. These are both transitional areas in the spine because the cervical vertebrae end as the thoracic vertebrae begin and the thoracic vertebrae end where the lumbar vertebrae begin. –The slightly different shapes of the vertebra create a unique junction in these areas where stress can become concentrated.
• Often, a release of muscular tension will allow these bones to return to a normal position.

Question 16

Elements of the Axial System:

Lumbar Vertebrae (7)

Answer 16

• The seven lumbar vertebrae have a larger and flatter vertebral body with a wide transverse process and do not receive bony support from the ribcage.
• They form a flat bridge between the ribcage and the pelvis.
• There is a slight to moderate kyphotic curve (rearward curvature) in this area of the back which varies amongst breeds.
• The lumbar vertebrae receive strong support from the supraspinous ligament above and from the musculature below.
• The SPs of the lumbar vertebrae have a slight cranial tilt (toward the head).

Question 17

Elements of the Axial System:

Sacral Vertebrae (3 Fused)

Answer 17

• The 3 sacral vertebrae are fused into the sacrum and form half of a floating joint with the ilium (part of the pelvis) called the sacroiliac joint.
• The ridge of the fused sacral vertebrae and the highest part of the left and right ilium (near the sacroiliac joints) create a high point in the hindquarter, commonly called the point of croup, the point of the sacrum, or the tuber sacral.

Question 18

Elements of the Axial System:

Caudal (coccygeal) Vertebrae (Approx. 20)

Answer 18

• After the sacrum, the dog has a chain of coccygeal vertebrae, which make up the tail. (This is in contrast to the human coccyx.)
• The number of caudal vertebrae (or coccygeal) varies based on breed of dog.
• The spinal cord does not extend through the coccygeal vertebrae, although the fascial membrane that surrounds the spinal cord does.

Question 19

Elements of the Axial System:

Ribs (13 pairs)

Answer 19

• The ribs (or costal bones) are part-bone and part-cartilage and attach at the sternum and at the vertebral column, as in the human.
• There are 13 pairs of ribs in the canine skeleton.
• The last rib does not have a sternal attachment and is referred to as the floating ribs.

Question 20

Elements of the Appendicular Skeleton :

Scapula

Answer 20

• The scapula is markedly different in the canine skeleton in both structure and function.
• Like the human, it is located over the upper portion of the ribcage and has a palpable ridge down its center called the spine of the scapula.
• The canine and human scapula has a deep fossa (anatomical hollow) both above and below the ridge.
• All serve as muscle attachment sites.
• The scapula has a cranial (or anterior) border and a caudal (or posterior) border rather than lateral and medial in the human.
• The scapula lies in the sagittal plane.
• Movements available at the scapula include elevation, depression, and movement cranially and caudally.
• Movement at the scapula is different than movement at the shoulder.
• The scapula is a specific bone while the shoulder is the joint between the scapula and the humerus.

Question 21

Elements of the Appendicular Skeleton:

Humerus

Answer 21

• The humerus lies between the scapula and the radius and ulnar bones of the forearm.
• The humerus forms the shoulder and elbow joints. It is short and thick with pronounced condyles (rounded ends).
• The humerus is more firmly set in the glenoid (cup-shaped) cavity than in humans although the scapula and shoulder are exclusively supported by soft tissue structures.

Question 22

Elements of the Appendicular Skeleton:

Radius and Ulna

Answer 22

• The radius and ulna make up the forearm and form part of the elbow (top) and the wrist (bottom).
• The ulna has a landmark called the olecranon process (Point of Elbow).
• In young animals, the radius is the larger of the two discrete forearm bones.
• In adults, the radius and ulna become fused to stabilize movement in the sagittal plane and limit movement in the coronal plane.
• The olecranon process (proximal end of the ulna) is the site of several muscle attachments of particular concern to the massage practitioner.

Question 23

Elements of the Appendicular Skeleton:

Carpals

Answer 23

The seven carpal bones are similar to the human wrist. The carpal bones are:

• Radial carpal
• Ulnar carpal
• Accessory carpal
• First carpal
• Second carpal
• Third carpal
• Fourth carpal

The accessory carpal bone is an important site to be familiar with as it can contribute to tendon stress when misaligned due to muscular tension originating in the shoulder. For the context of this class it is not necessary to know the individual carpal bones, but it is valuable for future study.

Question 24

Elements of the Appendicular Skeleton:

Metacarpals, Phalanges, and Claws

Answer 24

The dog is considered a digitigrades quadruped, meaning that they walk on their toes (digits). Below the carpus, the bones are similar as those in the human hands. The five metacarpals and the phalanges (digital bones) extend from the wrist to the toes. In-between the phalanges are numerous small floating bones called the sesamoid bones. They are attached in tendons of muscles.

The metacarpal bones are:

• First metacarpal • Second metacarpal • Third metacarpal • Fourth metacarpal • Fifth metacarpal

The phalanges occur at three levels:

• Proximal • Middle • Distal

The toe nails (claws) are separate from the phalanges. They are encased in the ungula crest.

Question 25

Elements of the Appendicular Skeleton:

Pelvis

Answer 25

• The ilium, ischium, and pubis bones articulate along tight suture lines to form the os coxae or pelvis.
• Where these bones meet, a cup is formed called the acetabulum.
• This is where the pelvis and femur connect to form the hip joint which is called the coxofemoral joint.
• The pelvis of the dog is much different in shape and position from that of the human skeleton, due to the different postural orientation of the quadruped and the biped.
• There is a far less pronounced bowl-like structure in the canine.
• Also, the body of the pelvis is long and more horn-like or T-shaped in appearance.
• There are important bony landmarks on the pelvis including the tuber coxae (Point of the Haunch).
• Other landmarks are the sacral tuberosity (Point of the Croup) and the ischial tuberosity (Point of Buttock).

Question 26

Elements of the Appendicular Skeleton:

Femur

Answer 26

The thighbone is called the femur and articulates at the pelvis to form the hip joint.

• A landmark of the femur is the greater trochanter (Point of Hip). -The joint of the femur and the tibia is called the stifle and represents the actual or true knee.
• Like the human knee, the stifle possesses a floating patella (kneecap).
• This joint is of frequent concern due to the increasing number of injuries to the anterior cruciate ligament in dogs.

Question 27

Elements of the Appendicular Skeleton:

Tibia and Fibula

Answer 27

• The fibula and tibia run between the stifle joint to the hock.
• They are very similar to the same bones in the human which form the calf.

Question 28

Elements of the Appendicular Skeleton:

Hock (ankle)

Answer 28

• The tarsus bones are comparable to the human ankle, but are referred to as the hock in the dog.
• There are seven tarsal bones.
• The talus bone (tibial tarsal), located medially, is in contact with the distal end of the tibia and is shaped like the human ear.
• The calcaneus bone (fibular tarsal) has a bony landmark called the calcaneal tuberosity, located laterally, forms the point of the hock.
• Below the central tarsal bone are four smaller plates of other tarsal bones:

• First tarsal • Second tarsal • Third tarsal • Fourth tarsal

-It is not necessary to know the individual bones of the hock by name, except for the calcaneus and talus as they provide bony landmarks and attachment sites for the muscles.

Question 29

Bony Landmarks

Answer 29

-Once you are comfortable knowing the bones and joints you can begin to study the various landmarks or sites on the bones.
-Bones are not smooth, but instead have many features such
as bumps, ridges, curves and dents.
-These geographical features have specific names and are common attachment sites for the tendons and ligaments we will study.

Question 30

Bony Landmarks

General terms used to describe bony landmarks.

Answer 30

Term Meaning Example
Arch arc inguinal arch

Condyle knuckle lateral femoral condyle

Crest prominent ridge crest of the ilium

Epicondyle above the knuckle medial epicondyle

Fossa bowl supraspinous fossa

Glenoid cup shaped supraglenoid fossa

Process projection spinous process

Spine ridge spine of the scapula
Trochanter large process greater trochanter

Tuber root or bulb tuber coxae

Tubercle small round bump lesser tubercle of the humerus

Tuberosity large round bump radial tuberosity