Skeletal System

VTT 235 Anatomy & Pathology Lab

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.

Functions

SupportProtectionStorageMovementBlood cell formation

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.

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.

Bone Structure…

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

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.

Bone Formation

Endochondral-Long bonesA cartilage model develops within the embryo.The cartilage is replaced with osteoblasts.Osteoclasts remove bone from the diaphysis forming the marrow cavity.A narrow band of cartilage still persists (growth plate) to allow the bone to lengthen and grow.

Intramembranous-Skull bonesOsteoblasts produce bone between 2 layers of fibrous CT.There is no cartilage template.

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

Bone Shapes

Irregular bones-A “miscellanous” category.Ex. VertebraeThis category also includes SESAMOID bones-

Named because early anatomists thought these bones resembled sesame seeds.Bones present in some tendons like the patella.

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.

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 bonePeriosteum- membrane that surrounds a bone.Medullary Cavity- the space that houses bone marrow.

Bone FeaturesCondyle- 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

Axial Skeleton

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.

Skull- External Cranium

Occipital bone- a single bone that forms the base of the skull.Interparietal bonesParietal bones- for the dorso-lateral wall of the cranium.

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.

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- hammerIncus- anvilStapes- stirrup

External Facial BonesIncisive 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).

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.

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.

Internal Facial Bones

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

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.

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- neckThoracic- chestLumbar- abdomenSacral- pelvisCoccygeal- tail

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.

Vertebrae

Formulas-**Dog- C7, T13, L7, S3, Cy20-23

**Cat- C7, T13, L7, S3, Cy5-23

Horse- C7, T18, L6, S5, Cy15-21

AxisAtlas

Vertebral Anatomy

IVDD

Disk extrusion

OUCH!!!

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.

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.

Sternum

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

Appendicular Skeleton

Limbs & significant features

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.

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.

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.

Radius

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

Carpus, Metacarpus, Tarsus, Metatarsus, & Phlanges

Equine Thoracic Limb

Rear View

HORSE:ScapulaHumerus**Radius/ulna (fused)CarpusAccessory carpalMetacarpals-

“Cannon Bone” (#3)Splint Bones (#2 & #4)

Proximal sesamoidsPhalanx’s-

Proximal- P1- Long PasternMiddle- P2- Short PasternDistal- P3- Coffin

Distal sesamoid- Navicular

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.

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.

Pelvis

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

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.

Femur

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

Femur

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

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.

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.

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.

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.

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.

Equine Pelvic Limb

PelvisFemurPatellaFibula & TibiaHock jointSplint & Cannon bonesFetlock & SesamoidsP1P2P3

Visceral Skeleton

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

Laboratory

Factors That Influence Bone Growth, Remodeling & Repair

Minerals-Calcium & Phosphorus- make bones hardMagnesium- deficiency inhibits osteoblasts

Vitamins-Vitamin A- controls the activity of osteoblasts and osteoclastsVitamin B12- may inhibit osteoblast activityVit. C- Helps maintain the bone matrix, deficiency inhibits bone growth & delays fracture repairVit. D- helps increase the absorption of calcium

Factors That Influence Bone Growth, Remodeling & Repair

Hormones-Growth Hormone- (anterior pituitary) promotes general growth of all body tissuesSex Hormones- promotes tissue repairInsulin- promotes normal bone growth and maturityThyroid Hormones- promotes normal bone growth and maturityCalcitonin- inhibits osteoclastsParathyroid Hormone- promotes bone reabsorption

THE END