Section 1 Lecture Material

Cranial

• Toward the head

• Opposite of caudal

Caudal

• Toward the butt

• Opposite of cranial

Rostral

• Toward the nose

• Used with caudal when referring to areas on the head instead of using cranial

Dorsal

• Toward the top of the back

• Opposite of ventral

Ventral

• Toward the belly

• Opposite of dorsal

Palmar

• the underside of the front feet

• Used in conjunction with dorsal when referring to the front feet

Plantar

• The underside of the hind feet

• Used in conjunction with dorsal when referring to the hind feet

Proximal

• Toward the trunk

• Opposite of distal and used for appendages only

Distal

• Away from the trunk

• Opposite of proximal and used for appendages

Medial

• Toward the midline

• Opposite of lateral

Lateral

• Away from the midline

• Opposite of medial

Ipsilateral

• on the same side

• Opposite of contralateral

Contralateral

• on the opposite side

• Opposite of ipsilateral

Superficial

• closer to the surface

• Opposite of deep

Deep

• farther from the surface

• Opposite of superficial

Axial

• Toward the axis of the foot

• Opposite of abaxial

Abaxial

• Away from the axis of the foot

• Opposite of axial

Dorsal Recumbency

• The dog is placed on its dorsal side (laying on its back)

Sternal Recumbency

• The dog is placed on its sternal side (laying on its belly)

• Also known as ventral recumbency

Right and left lateral recumbency

• The dog is placed on one of its lateral sides

• Left lateral recumbency = laying on its left side

• Right lateral recumbency = laying on its right side

Dorsal Plane

• divides the body into dorsal and ventral sides

Sagittal Plane

• divides the body into right and left sides (does not need to be equal and can have multiple sagittal planes

Median / Midsagittal Plane

• divides the body into equal right and left halves

• Midline

Transverse planes

• create cross-sections (ex. Cranial and caudal; proximal and distal sides)

Tissues

A group of specialized cells working together to perform a common function

Organs

A somewhat independent part of the body that performs a particular functions

Usually composed of two or more basic tissues

4 types of basic tissues

• Epithelial

• Connective

• Muscle

• Nervous

Epithelial Tissue

• Ex. Epidermis, endothelium

• Lines internal body tubes and external body surfaces, forms glands

Connective Tissue

• Ex. Adipose tissue (fat), blood, bone, cartilage, fibrous connective tissue

• Connects and supports body components, movement, insulation, energy storage, repair, nutrition

Muscle Tissue

• Ex. Skeletal, smooth, cardiac

• Body movement, movement of blood, movement of ingesta

Nervous Tissue

• Ex. Brain and spinal cord (CNS), Peripheral nerves, autonomic nervous system

• Receives, integrates, and transmits external and internal stimuli between external and internal environments

Fascia Functions

• provides support and structure

• Compartmentalizes and reduces friction, allowing muscles and organs to glide against each other

• Transmits and distributes mechanical forces (ex. Muscle contractions, trauma)

• Supports blood vessels, nerves, and lymphatics

• In some instances, it serves as muscle attachment

• Important for proprioception, due to its network of mechanoreceptors

Fascia

A continuous, interconnected network of connective tissue that exists throughout the body

It is composed of elastic fibers, collagen fibers, and fibroblasts

Types of fascia

• Superficial - hypodermis

• Deep - surrounds muscles, bones, nerves, vessels

• Parietal - lines body cavities

• Visceral - surrounds viscera

List the layers of the skin

• Epidermis (cutis)

• Dermis (corium)

• Hypodermis (subcutis, superficial fascia layer)

Epidermis (Cutis)

outermost layer of the skin

Composed of 5 layers of epithelial cells

Dermis (corium)

Middle layer of the skin

Contains glands, hair follicles, nerves, blood vessels, CT fibers (collagen and elastin)

Hypodermis (subcutis, superficial fascia layer)

Deepest layer of the skin

Composed of loose areolar connective tissue and fat

Hair

In dogs and cats, the follicles are simple shortly after birth, but are complex during adolescence and adulthood

Follicles in double coated dogs have one primary (guard) hair and multiple secondary (undercoat) hairs.

Cats have primary, intermediate, and secondary hairs

Vibrissa

Whiskers

Specialized hairs that are thicker and longer than primary hairs

Deeply rooted with follicles that sit within sinuses that are highly innervated with various sensory nerve endings

Pads

Specialized features of skin

• Epidermis - keratinized and conical, often smoother in cats than dogs

• Dermis - dense connective tissue and conical

• Hypodermis - thick fat pad that interspersed with connective tissue fibers, eccrine sweat glands

Nails

Specialized integument structures

• Epidermis - outer cornified layer, grows from germinal epithelium aka living epidermis just superficial to the dermis

• Dermis - the sensitive part of the nail which contains sensory nerve endings and blood vessels

• Ungual process - bony process deep to the dermis

Regions of the forelimb

• Scapular (pink) - scapula and surrounding features

• Brachium (yellow) - region between shoulder and elbow joints

• Antebrachium (green) - region between elbow and carpal joints

• Manus (blue) - carpus and distal

• Axilla (armpit) - cavity between the forelimb and thorax

Skeletal functions

• provides a frame for the body

• Movement (acts as attachment sites for muscles)

• Protection of vital organs

• Source of minerals (calcium and phosphorus)

• Hematopoiesis (making red blood cells)

Parts of the skeleton

• Axial - skull, vertebrae, ribs, sternebrae

• Appendicular - limbs

• Heterotropic - bone development in the soft tissue

Vertebral formula for cats and dogs

C7 T13 L7 S3 Cd20-23

Types of bones

• long - humerus, radius, ulna

• Short - carpals

• Flat - scapula, skull

• Irregular - vertebrae

• Sesamoid (embedded in tendons) - palmar and dorsal sesamoids, patella

• Pneumatic (contain air spaces) - mammalian skull bones with paranasal sinuses or bird bones

• Visceral / heterotopic (within soft tissue) - ossa cordis, os penis, os rostrale

Types of bone composition

• woven

• Lamellar

• Cortical / compact

• Cancellous / trabecular

Woven Bone

Arrangement of immature bone

Found in juvenile/developing bones and early fracture repair

Lamellar bone

Highly ordered arrangement of mature bone

Circular structure

Cortical / compact bone

Dense layers of lamellar bone

Cancellous / trabecular bone

Lattice arrangement of bony spicules deep to cortical bone

Identify the regions of a lone bone

• Epiphysis - enlarged proximal and distal ends

• Diaphysis / body - elongated central portion, contains marrow cavity

• Metaphysis - between epiphysis and diaphysis

• Physis / growth plate / epiphyseal plate - after closure of the physis, an ossified epiphyseal line remains

Bone remodeling

The reformation of existing bone due to normal biomechanical forces, damage / trauma, diet, or hormones (ex. Parathyroid, calcitonin, calcitriol, estradiol)

Remodeling is a constant, dynamic process involving bone resorption by osteoclasts and bone formation by osteoblasts

Bone linings

Hyaline cartilage - lines the superficial surface of subchondral bone

Periosteum - lines the superficial surface of non-articular areas

Endosteum - lines the deep surface of compact bone

Physes / growth plate / epiphyseal plate

Area at which long bones increase in length

Cartilaginous portions of long bones that exist between separate centers of ossification

Chondrocytes in a collagen matrix mature and are replaced by osteoblasts, osteoclasts, and osteocytes (cartilage becomes bone)

Medullary cavity

Consists of cancellous bone interspersed throughout either red or yellow marrow

Bone marrow can be samples from any area with red marrow (ribs, sternum, ilium, femur, tibia, humerus) or can be used for intraosseous (IO) access

Proximal humerus, proximal femur, and proximal tibia are most commonly used

Yellow bone marrow

Medullary cavities of adults contain predominantly yellow marrow, which contains a great deal of adipose tissue

The color is due to carotenoids in fat cells

During times of need, yellow marrow can be converted back to red marrow

Red bone marrow

Young animals have primarily red marrow, which has a great deal of hematopoietic tissue and is highly vascularized

The color is due to hemoglobin in erythroid cells

Red marrow is normally present in some adult bones, including ribs, sternum, ilium, femur, tibia, and humerus

What area is usually used for IO access in the forelimb?

The proximal humerus is usually used with specific interest in the flat area of the proximal lateral humerus just distal to the greater tubercle

List the bones of the thoracic girdle

• scapula

• Clavicle (cats only)

List the bones in the brachium

• humerus

List the bones in the antebrachium

• radius

• Ulna

List the bones in the manus

• carpus

• Metacarpus

• Digits

Identify the physes of the scapula

• supraglenoid

Identify the physes of the humerus

• proximal

• Distal

• Mid-condyle

• Medial epicondyle

• Lateral epicondyle

List the physes of the radius

• proximal

• Distal

List the physes of the ulna

• olecranon tuber

• Anconeal process

• Distal

What passes through the supracondylar foramen in cats?

• through this hole passes the brachial artery and the median nerve

• It is situated on the medial surface of the distal humerus

• Fractures can occur in this area, surgeons must take great care to not cause further damage to these features

Explain the relationship between the radius and ulna

The radius is craniomedial to the ulna proximally and craniomedial to the ulna distally

Joint

The union between two or more bones by fibrous, elastic, cartilaginous, or a combination of tissue

3 types of joints: fibrous, cartilaginous, synovial

Synsarcosis - a type of joint wherein bones are joined to one another via muscle (ex. Scapular attachment to the thorax by extrinsic muscles)

Fibrous joints

Relatively immovable joints with bones united by dense connective tissue

• Suture - between flat bones of the skull

• Syndesmosis - ex. Distal radioulnar joint

• Gomphosis - tooth in alveolar socket

Cartilaginous joints

Slightly moveable joints with bones united by cartilage, many are transient

• Synchondrosis (hyaline cartilage) - growth plates, costochondral junctions

• Symphysis (articular cartilage connected via fibrocartilage - mandibular symphysis, pelvic symphysis

Synovial joints

Apposing surfaces of bones are covered with hyaline articular cartilage, which act as shock absorbers during weight bearing and impact

Bones are connected by a joint capsule, which has two layers:

• fibrous layer - superficial layer, DFCT, attaches to apposing bones

• Synovial layer - deep layer, specialized CT, secretes synovial fluid (nutrition), attaches at the bone / cartilage junction

Other synovial structures (bursae, tendon sheaths) have the same structure of fibrous and synovial layers

Hyaline articular cartilage

One of three types of cartilage

Normal hyaline cartilage is smooth, shiny, and glaucous

As cartilage is damaged, it erodes, thus exposing subchondral bone, articular cartilage has limited ability to repair itself and areas of wear are eventually replaced with fibrocartilage which lacks hyaline’s resistance to compressive forces

Synovial fluid

A filtrate of plasma concentrated by synoviocytes

Function:

• lubrication - reduces friction between apposing surfaces

• Nutrition - hyaline cartilage, menisci, labrum, etc. are avascular; nutrients to these structures are supplied by synovial fluid via diffusion

Functional types of synovial

• ball and socket joint

• Hinge joint

• Ellipsoid joint

• Saddle joint

• Pivot joint

• Plane joint

Ball and socket joint

Ex. Glenohumeral

Movement - in many planes: flexion/extension, internal/external rotation, side-to-side

Hinge joint

Ex. Umeroradial and humeroulnar

Movement - flexion and extension

Ellipsoid joint

Ex. Carpus, metacarpophalangeal, prox. Interphalangeal

Movement - primarily flexion and extension, with some medial to lateral movement

Saddle joint

Ex. Distal interphalangeal joint

Movement - primarily flexion and extension, with some medial to lateral movement

Pivot joint

Ex. Proximal radioulnar joint

Movement - rotation

Plane joint

Ex. Articular surfaces between vertebrae

Movement - flat joints that slide against each other

Synovial bursa

A small sac containing synovial fluid

Like joint capsules, there is an outer fibrous layer and an inner synovial layer

Bursae are located between highly mobile structures and structures under high tension (usually between tendon and bone, but may also be between fascia and skin) Thus, they act like cushions and reduce friction to prevent damage to said structures

Synovial tendon sheaths

Tube-like structures surrounding a tendon or tendons

They provide lubrication and reduce friction

Ex. Proximal tendon of biceps brachii m. Or distal tendons of superficial and deep digital flexor mm.

Osteochondritis dessicans (OCD)

Osteochondrosis is a group of disorders of bone development most commonly in large dog breeds on the humeral head (followed by femoral condyles)

It is caused by epiphyseal ischemia, which results in defective growth of the subchondral bone

The overlying articular cartilage becomes excessively stressed and tears, resulting in the formation of a cartilage flap

Flexion

Bending a joint

Ex. Decreasing angle of the flexor surface

Extension

Straightening a joint

Ex. Increasing the angle of the flexor surface

Rotation

Moving in a circular motion (external or internal)

• Supination - movement of palmar or plantar surface upward

• Pronation - movement of palmar or plantar surface to neutral

Abduction

Moving away from the midline

Adduction

Moving toward the midline

Protraction

Moving the limb cranially

Retraction

Moving the limb caudally