1. Skeletal System
VTT 235 Anatomy & Pathology Lab

2. Skeletal System
The skeleton is the framework of bones
that supports and protects the internal
structures.
Has an excellent capacity to repair
itself after an injury.
Bone is composed of a sparse population
of cells embedded in a hard substance
called the matrix.

3. Functions
Support
Protection
Storage
Movement
Blood cell formation

4. Bone Structure
Cancellous Bone-
Consists of tiny spicules of bone that
appears randomly arranged with lots of
spaces between them.
The spaces between the spicules are
occupied by bone marrow.

5. Bone Structure…
Compact Bone-
Very heavy, dense and
strong.
Makes up the shaft of
long bones, and the
outside layer of all bones.
Haversian Canals run
lengthwise and contains
blood vessels and nerves
that supply osteocytes.

6. Bone Structure…
Compact Bone-
Volkmann’s canals
run across bones and
contain blood vessels.

7. Bone Cells
Osteoblasts-
Cells that form bone.
Secretes the matrix of bone and then supplies the
minerals necessary to cause it to harden.
Once osteoblasts become trapped in the ossified
matrix they create, they become…
Osteocytes-(mature dormant bone cell) which
are always ready to return to osteoblasts and
form new bone if an injury makes that
necessary.
Osteoclasts- removes bone where it is not
needed.

8. Bone Formation
Endochondral- Intramembranous-
Long bones Skull bones
A cartilage model develops Osteoblasts produce bone
within the embryo. between 2 layers of fibrous
The cartilage is replaced CT.
with osteoblasts. There is no cartilage
Osteoclasts remove bone template.
from the diaphysis forming
the marrow cavity.
A narrow band of cartilage
still persists (growth plate)
to allow the bone to lengthen
and grow.

9. Bone Shapes
Long bones-
Longer than wide, most limb bones.
Short bones-
Shaped like small cubes.
Ex. Carpal & tarsal bones.
Flat bones-
Two thin plates of compact bone separated
by a thin layer of cancellous bone.
Skull bones, pelvis, scapula

10. Bone Shapes
Irregular bones-
A “miscellanous” category.
Ex. Vertebrae
This category also includes SESAMOID
bones-
Named because early anatomists thought these
bones resembled sesame seeds.
Bones present in some tendons like the patella.

11. Bone Marrow
Fills the spaces within bones.
Red bone marrow-
Hematopoietic tissue- forms blood cells.
Yellow bone marrow-
Consists primarily of adipose CT.
Does not produce blood cells.

12. Parts of a
Bone
Articular Cartilage- around
the ends where the joint
meets.
Growth Plate- the point where
new bone grows (epiphyseal
cartilage).
Diaphysis- long portion of a
bone.
Epiphysis- the end of a bone
Periosteum- membrane that
surrounds a bone.
Medullary Cavity- the space
that houses bone marrow.

13. Bone Features
Condyle- a large prominence.
Foramen- hole to accomadate
blood vessels and nerves.
Fossa- a hollow depression in a
bone.
Groove- a depression for
tendons, nerves or vessels.
Head- “ball” of a ball & socket.
Trochanter- found only on the
femur.
Tubercle- small rounded
process on the end of a bone.
Tuberosity- a roughened
process.
Please refer to your handout
for these processes

14. Axial Skeleton

15. Skull
The most complex part of the skeleton.
Consists of 37-38 separate bones.
Most skull bones are united by jagged,
immovable joints called sutures.
External cranium- formed by 11 bones.

16. Skull- External Cranium
Occipital bone- a
single bone that
forms the base of
the skull.
Interparietal bones
Parietal bones- for
the dorso-lateral
wall of the cranium.

17. Skull- External Cranium
Temporal bones-
Forms the lateral
walls of the cranium.
Contains the middle
and inner ear
structures.
Frontal bones-
Forms the forehead
and a portion of the
orbit.
Contains the sinuses.

18. Skull- Internal Cranium
Sphenoid bone- forms the bottom of the
cranium.
Contains the pituitary fossa.
Ethmoid bone- located rostral to the
sphenoid bone.
Ear bones (ossicles)- functions to transmit
vibrations from the tympanic membrane to
the cochlea.
Malleus- hammer
Incus- anvil
Stapes- stirrup

19. External Facial Bones
Incisive bones- houses the upper incisor
teeth.
Nasal bones- forms the bridge of the nose.
Determines dolichocephalic/brachyocephalic
Maxillary Bones- make up most of the upper
jaw.
House the upper canine teeth & cheek teeth.
Forms a portion of the hard palate (roof of the
mouth).

20. External Facial Bones
Lacrimal bones- form the medial portion of
the orbit and houses the lacrimal sacs.
Zygomatic bones- forms a portion of the
orbit.
Joins with the temporal bone to form the
ZYGOMATIC ARCH (cheekbones).
Mandible- lower jaw.
Houses all the lower teeth.
The 2 sides are united by the MANDIBULAR
SYMPHYSIS.

21. Internal Facial Bones
Palatine bones- forms the caudal
portion of the hard palate.
Pterygoid bones- supports the lateral
walls of the pharynx.
Vomer bone- forms part of the nasal
septum.

22. Internal Facial Bones
Turbinates- four
thin, scroll-like
bones that fills most
of the space in the
nasal cavity.

23. Internal Facial Bones
Hyoid Bone-
Looks like an “H”.
Located just above
the larynx.
Supports the base of
the tongue, the
pharynx, the larynx,
and helps with
swallowing.

24. The Spinal Column
Made up of a series of individual irregular
bones.
Vertebra- singular Vertebrae- pleural
Extends from the skull to the tip of the tail.
Divided into 5 regions:
Cervical- neck
Thoracic- chest
Lumbar- abdomen
Sacral- pelvis
Coccygeal- tail

25. Vertebrae Characteristics
Consists of a body, an arch, and a group of
processes.
Spinous process- a single, dorsally projecting
process.
Transverse process- two laterally projecting
processes.
The body is the strongest portion.
Vertebral bodies are separated by
INTERVETEBRAL DISKS which act as
cartilaginous shock absorbers.
The arches form the SPINAL CANAL which
houses and protects the spinal cord.

27. Vertebrae
Formulas-
**Dog- C7, T13, L7, S3, Cy20-23
**Cat- C7, T13, L7, S3, Cy5-23
Horse- C7, T18, L6, S5, Cy15-21
Axis
Atlas

28. Vertebral Anatomy

30. IVDD
Disk extrusion

31. OUCH!!!

32. Ribs
Flat bones that form
the lateral walls of the
thorax.
The number of pairs of
ribs is equal to the
number of thoracic
vertebrae.
Ventral ends of ribs
have 2 parts:
A dorsal part made of
bone.
A ventral part made of
cartilage called COSTAL
CARTILAGE.

33. Ribs
The junction of bone and cartilage is
called the COSTOCHONDRAL
JUNCTION.
Ribs whose cartilages join the sternum
are called “sternal ribs”.
Asternal ribs- make up the caudal
portion of the thorax.
Floating rib- on either side, the last
rib.

35. Sternum
“Breastbone”
Forms the floor of the thorax.
Made up of STERNEBRAE.
Manubrium- 1st sternabra
Xiphoid- last sternabra

36. Appendicular
Skeleton
Limbs & significant features

37. Scapula
Most proximal bone
of the thoracic limb.
The prominent
projection on the
lateral surface is
called the spine.
Glenoid Cavity-
forms the socket for
the shoulder joint.

38. Humerus
Opposite the head is the
greater tubercle where
the shoulder muscles
attach.
The distal condyles form
the elbow joint.
Just above the condyles is
a deep indentation called
the olecranon fossa.

39. Ulna
Olecranon process- forms the point of the elbow,
and attaches the triceps brachii muscle.
Trochlear notch- half-moon shaped process that
wraps around the humeral condyle to form a tight
elbow joint.
The Anconeal process is located at the top of the
trochlear notch.

40. Radius
Main weight-bearing bone of the antebrachium.
Has facets that articulate with the proximal end of
the ulna.

41. Carpus,
Metacarpus,
Tarsus,
Metatarsus, &
Phlanges

42. Equine Thoracic Limb
HORSE:
Scapula
Humerus
**Radius/ulna (fused)
Carpus
Accessory carpal
Metacarpals-
“Cannon Bone” (#3)
Splint Bones (#2 & #4)
Proximal sesamoids
Phalanx’s-
Proximal- P1- Long Pastern
Middle- P2- Short Pastern
Distal- P3- Coffin
Distal sesamoid- Navicular
Rear View

43. Pelvis
“Os coxae”
The two halves of the pelvis are joined
by the pelvic symphysis.
The pelvis consists of 3 individual
bones: the ilium, ischium, and the pubis.
All 3 bones come together to form the
acetabulum which is the socket for the
hip joint.

44. Pelvis
Ilium-
Most cranial bone of
the pelvis.
The bone that forms
the sacroiliac joint.
The tuber coxae
projects laterally and
forms the point of
the hip.

45. Pelvis
Ischium-
The most caudal
pelvic bone.
You are sitting on
your ischia!
The main rear-
projecting process is
the ischial
tuberosity.

46. Pelvis
Pubis-
The smallest of the 3
pelvic bones.
Forms the cranial portion
of the pelvic floor.
Obutrator foramen- two
large holes on either side
of the pelvic symphysis.

47. Femur
Long bone of the thigh.
Head- found at the
proximal end.
Greater trochanter-
only found on the
femur, opposite the
head.

48. Femur
Both medial and
lateral condyles are
found on the distal
end.

49. Patella
The largest seasmoid
bone in the body.
Formed in the distal
tendon of the large
quadriceps muscle.
Flabellae- two small
seasmoid bones located
in the calf muscle just
above and behind the
femoral condyles.

50. Tibia
Main weight-bearing
bone of the lower
leg.
The tibial
tuberosity is the
forward-facing point
of the triangle which
continues distally as
a ridge called the
tibial crest.

51. Fibula
The thin bone that
parallels the tibia.
Mainly serves as a
muscle attachment
site.
Lateral malleous- a
palpable process
found at the distal
end.

52. Tarsus
“ankle”, “hock”
Consists of 2 rows of short bones.
Proximal row- tibial tarsal bone, fibular tarsal bone,
& the central tarsal bone is tucked behind the 2
larger bones.

53. Tarsus
Calcaneal tuberosity- projects upward and
backward to form the point of the hock.
It acts as the point of attachment for the
gastrocnemius tendon and corresponds to our
heel.

54. Equine Pelvic
Limb
Pelvis
Femur
Patella
Fibula & Tibia
Hock joint
Splint & Cannon bones
Fetlock & Sesamoids
P1
P2
P3

55. Visceral Skeleton
Consists of bones that form in soft organs
(viscera).
Os penis
Os cordis- a bone in the heart of sheep and
cattle.

56. Laboratory

57. Factors That Influence Bone
Growth, Remodeling & Repair
Minerals-
Calcium & Phosphorus- make bones hard
Magnesium- deficiency inhibits osteoblasts
Vitamins-
Vitamin A- controls the activity of osteoblasts and
osteoclasts
Vitamin B12- may inhibit osteoblast activity
Vit. C- Helps maintain the bone matrix, deficiency
inhibits bone growth & delays fracture repair
Vit. D- helps increase the absorption of calcium

58. Factors That Influence Bone
Growth, Remodeling & Repair
Hormones-
Growth Hormone- (anterior pituitary) promotes
general growth of all body tissues
Sex Hormones- promotes tissue repair
Insulin- promotes normal bone growth and maturity
Thyroid Hormones- promotes normal bone growth
and maturity
Calcitonin- inhibits osteoclasts
Parathyroid Hormone- promotes bone reabsorption

59. THE
END