Chapter 3 (Vet med)

Functions and Overview of the Musculoskeletal System

• The musculoskeletal (muhs-kyoo-lo-skehl-eh-tahl) system consists of two distinct systems that work together to support the body and enable movement: the skeletal system and the muscular system.

• Skeletal System Functions:

  • Forms the structural framework that supports and protects an animal's body.

  • Encloses red bone marrow, which is responsible for hematopoiesis (forming red blood cells, white blood cells, and clotting cells).

  • Facilitates body movement in conjunction with joints, cartilage, tendons, and ligaments.

• Key Structural Components:

  • Bones: Provide rigid support and framework.

  • Cartilage: Protects the ends of bones where they contact each other and provides flexible support in structures such as the ear and nose.

  • Joints: Aid in movement by linking components of the skeletal framework.

  • Tendons: Connect muscle to bone to enable voluntary and involuntary movement.

  • Ligaments: Connect bone to bone to support and stabilize joints.

Connective Tissue Characteristics

• The entire skeleton is composed of various types of connective tissue.

• Definition: Connective tissue is characterized by having a relatively small proportion of cells embedded within a large extracellular matrix.

• Function: It binds together and supports various anatomical structures throughout the body.

• Connective tissues associated with the skeletal system include bone, tendons, ligaments, and cartilage.

Bone Microstructure, Development, and Physiology

• Bone is one of the hardest connective tissues in the animal body.

• Embryonic Skeleton: Initially composed of cartilage and fibrous membranes, which gradually harden into bone prior to birth.

• Ossification (ohs-ih-fih-kā-shuhn):

  • The continuous physiological process of forming bone from fibrous tissue.

  • Begins embryonically and continues until full physical maturity is reached (a timeline that varies by species).

• Bone Remodeling:

  • Normal bone undergoes a constant dual process of building up (formation) and breaking down (resorption) throughout an animal's life.

  • This balanced mechanism allows bone to heal and repair structural damage.

  • Maintained by a continuous balance between osteoblasts and osteoclasts.

Specialized Bone Cells

• Osteoblasts (ohs-tē-ō-blahsts):

  • Combining forms: oste/o = bone, -blasts = immature.

  • Immature bone cells responsible for producing bony tissue.

  • As osteoblasts mature and become embedded in the bone matrix, they develop into osteocytes.

• Osteoclasts (ohs-tē-ō-klahsts):

  • Combining forms: oste/o = bone, -clasts = break.

  • Phagocytic cells that absorb and eat away bony tissue from the medullary cavity of long bones.

• Osteocytes (ohs-tē-ō-sītz):

  • Mature bone cells that maintain established bone tissue.

• Combining Forms for Bone: oste/o, oss/e, oss/i.

Microscopic Structure of Compact Bone

• Compact bone is organized into microscopic structural units called osteons.

• Each osteon contains a central canal housing blood vessels and nerves.

• The bone matrix is deposited in concentric circular arrangements around the central canal.

• Darkly stained osteocytes are housed within cavities (lacunae) scattered throughout the circular matrix.

Bone Marrow Types and Hematopoiesis

• Red Bone Marrow:

  • Located predominantly within cancellous bone.

  • Functionally hematopoietic (hēm-ah-tō-poy-eht-ihck).

  • hemat/o = blood

  • -poietic = pertaining to formation

  • Produces red blood cells, white blood cells, and clotting cells (platelets).

• Yellow Bone Marrow:

  • Located within the medullary (mehd-yoo-lahr-ē) cavity (the inner hollow space of long bones).

  • Composed primarily of fat cells and functions as a fat storage area.

  • In adult animals, yellow bone marrow gradually replaces red bone marrow in long bone shafts.

Pathological Changes in Bone Structure

• -malacia: Suffix denoting abnormal softening of tissue (e.g., osteomalacia).

• -sclerosis: Suffix denoting abnormal hardening of tissue (e.g., osteosclerosis).

Word Parts for the Skeletal System

• epi- = above

• physis = growth

• dia- = between

• peri- = surrounding

• oste/o- = bone

• -um = structure

• endo- = within or inner

• meta- = beyond

Structural Anatomy and Terminology Applied to Bone

Types of Bone Tissue

• Cortical Bone (kōr-tih-kahl):

  • Hard, dense, strong bone that forms the protective outer layer of bones.

  • Also referred to as compact bone.

  • Derivation: cortex means "bark" or "shell" in Latin.

• Cancellous Bone (kahn-sehl-uhs):

  • Lighter, less dense, and structurally weaker bone found at the ends and inner portions of long bones.

  • Also referred to as spongy bone.

  • Derivation: cancellous means "latticework" in Latin.

Anatomical Regions of Long Bones

• Epiphysis (eh-pihf-ih-sihs):

  • The wide end of a long bone, covered with articular cartilage and composed internally of cancellous bone.

  • Proximal Epiphysis: Located nearest the midline of the body.

  • Distal Epiphysis: Located farthest away from the midline of the body.

• Diaphysis (dī-ahf-ih-sihs):

  • The long shaft of a bone, composed mainly of compact/cortical bone.

• Physis (fī-sihs):

  • The cartilage segment of a growing long bone involved in bone growth in length.

  • Commonly referred to as the growth plate or epiphyseal cartilage.

• Metaphysis (meh-tahf-ih-sihs):

  • The wider part of the long bone shaft located immediately adjacent to the physis.

  • In fully mature adult animals, it is considered a part of the epiphysis.

• Periosteum (pehr-ē-ohs-tē-uhm):

  • Tough, fibrous vascular membrane forming the outer covering of bone surfaces.

• Endosteum (ehn-dohs-tē-uhm):

  • Tough, fibrous membrane forming the tissue lining of the internal medullary cavity.

Anatomical Classification of Bones

• Long Bones: Bones consisting of a main shaft, two expanded ends, and a central marrow cavity (e.g., femur, humerus).

• Short Bones: Cube-shaped bones with no distinct central marrow cavity (e.g., carpal and tarsal bones).

• Flat Bones: Thin, expanded, flattened bones providing protection or broad muscle attachment (e.g., pelvis, scapula).

• Pneumatic Bones: Bones containing air-filled spaces or sinuses (e.g., frontal bone of the skull).

• Irregular Bones: Unpaired bones with complex, miscellaneously shaped structures (e.g., vertebrae).

• Sesamoid Bones: Small bones embedded directly within a tendon or joint capsule to reduce friction (e.g., patella).

  • Exception: The distal sesamoid bone (navicular bone) of the horse.

Cartilage Characteristics and Anatomy

• Cartilage (kahr-tih-lihdj):

  • Form of connective tissue that is significantly more elastic and flexible than bone.

  • Combining form: chondr/o.

• Articular Cartilage (ahr-tihck-yoo-lahr):

  • Specific type of hyaline cartilage covering the joint-articulating surfaces of bones to minimize friction.

• Meniscus (meh-nihs-kuhs):

  • Curved pad of fibrous cartilage found within specific complex joints (such as the canine stifle joint).

  • Serves to cushion, absorb, and distribute shock forces applied to the joint.

Arthrology: Joints and Articulations

• Joints or Articulations (ahr-tihck-yoo-lā-shuhns):

  • Structural connections formed between two or more adjacent bones.

  • Articulate: To join together in a manner that permits relative motion between constituent parts.

  • Combining form: arthr/o.

Functional Classifications of Joints

1. Synarthroses (sihn-ahrth-rō-sēz):

   • Immovable joints usually bound tightly together by dense fibrous connective tissue.

   • Suture (soo-chuhr):

     • Jagged, interlocking structural line where skull bones meet to form a rigid, nonmovable joint.

   • Fontanelle (fohn-tah-nehl):

     • Unossified soft spot remaining at the junction of cranial sutures in young animals, which typically closes completely after birth.

2. Amphiarthroses (ahm-fih-ahrthr-ō-sēz):

   • Semimovable joints that permit limited motion.

   • Symphysis (sihm-fih-sihs):

     • Joint where two bones are joined and held firmly together by cartilage so that they function structurally as a single unified unit; also called a cartilaginous joint.

     • Mandibular Symphysis: Fusion point where the left and right halves of the mandible meet at the chin.

     • Pubic Symphysis: Structural fusion point joining the left and right pubic bones of the pelvis.

3. Diarthroses (dī-ahrth-rō-sēz):

   • Freely movable joints, commonly termed synovial joints.

Subtypes of Synovial (Diarthrodial) Joints

• Ball-and-Socket Joints:

  • Also termed enarthrosis (ehn-ahr-thrō-sihs) or spheroid joints.

  • Consist of a globular head fitting into a cuplike cavity, allowing a wide range of motion in many directions (e.g., hip joint, shoulder joint).

• Arthrodial Joints / Condyloid Joints (ahr-thrō-dē-ahl / kohn-dih-loyd):

  • Joints featuring oval projections (condyles) fitting into matching shallow sockets (e.g., carpal joints where the radius meets the carpus).

• Trochoid Joints / Pivot Joints (trō-koyd / pih-voht):

  • Pulley- or ring-shaped joints permitting rotational movement around a single axis (e.g., joint connecting the atlas to the axis).

• Ginglymus Joints / Hinge Joints (jihn-glih-muhs):

  • Joints permitting angular movement constrained exclusively to a single plane or direction (e.g., elbow joint, canine stifle joint).

• Gliding Joints:

  • Flat or slightly curved articular surfaces that slide or glide across one another (e.g., radioulnar joint, articulating surfaces between successive vertebral processes).

• Saddle Joint:

  • Unique joint structure present in primates located specifically at the carpometacarpal joint of the thumb.

  • Permits the thumb to flex, extend, abduct, adduct, and circumduction.

Supporting Soft Tissue Structures

Ligaments and Tendons

• Ligament (lihg-ah-mehnt):

  • Dense band of fibrous connective tissue that connects one bone to another bone, functioning to stabilize joint structures.

  • Combining form: ligament/o.

• Tendon (tehn-dohn):

  • Dense band of fibrous connective tissue that connects muscle to bone, translating muscular contraction into movement.

  • Combining forms: ten/o, tend/o, tendin/o.

  • Memory Aid: Muscle and tendon share the exact same number of letters (6 letters), and the Achilles tendon attaches the calf muscle directly to bone.

Bursae and Synovial Structures

• Bursa (bər-sah):

  • Fibrous, fluid-filled sac acting as a cushion to reduce friction in movement areas where tendons pass over bones (e.g., shoulder joint).

  • Plural: Bursae (bər-sā).

  • Combining form: burs/o.

• Synovial Membrane and Fluid:

  • Bursae and synovial joints are lined internally by a specialized synovial membrane (sih-nō-vē-ahl).

  • The synovial membrane secretes viscous synovial fluid, which acts as a dynamic lubricant ensuring smooth joint surface glides.

  • Combining forms: synovi/o, syno-.

Divisions of the Animal Skeleton

• The total skeletal framework is descriptively partitioned into two major components: the axial skeleton and the appendicular skeleton.

• Axial Skeleton (ahcks-ē-ahl):

  • Represents the primary central framework aligned directly along the body's center of gravity.

  • Consists of the skull, auditory ossicles, hyoid bones, vertebral column, ribs, and sternum.

• Appendicular Skeleton (ahp-ehn-dihck-yoo-lahr):

  • Represents the peripheral frame connected to the central axis.

  • Consists of the upper and lower extremities, shoulder girdle, and pelvic girdle.

  • Etymology: The root append means "to add" or "to hang," representing anatomical appendages hanging directly from the axial core.

The Axial Skeleton: Bones of the Skull and Cranium

Cranial Bones

• Cranium (krā-nē-uhm):

  • The precise dorsal portion of the skull enclosing and protecting the brain.

  • Combining form: crani/o.

• Frontal Bone (frohn-tahl):

  • Forms the roof of the cranial cavity and the forehead/cranial rostral region.

  • In horned species, the cornual process (kōrn-yoo-ahl), which forms the core of the horn, arises directly from the frontal bone.

• Parietal Bones (pah-rī-ih-tahl):

  • Paired bones forming the roof and sides of the caudal cranial cavity.

• Occipital Bone (ohck-sihp-ih-tahl):

  • Forms the caudoventral aspect of the cranial cavity.

  • Features the foramen magnum (fō-rā-mehn mag-nuhm), the large central passage through which the brainstem connects to the spinal cord.

  • Foramen: Any anatomical opening through bone for the passage of neural or vascular tissues.

  • Magnum: Means "large".

• Temporal Bones (tehm-pohr-ahl):

  • Paired bones forming the lateral walls and base of the cranium.

• Sphenoid Bones (sfeh-noyd):

  • Paired bones forming part of the cranial base as well as portions of the floor and lateral walls of the bony orbit (eye socket).

• Ethmoid Bone (ehth-moyd):

  • Forms the rostral border of the cranial cavity, separating it from the nasal passages.

• Incisive Bones (ihn-sī-sihv):

  • Form the rostral part of the hard palate and lower margin of the nares.

• Pterygoid Bones (tahr-ih-goyd):

  • Form the lateral structural walls of the nasopharynx.

• Sinuses (sīn-uhs-ehz):

  • Air- or fluid-filled cavities located within specific skull bones (e.g., frontal sinus).

Facial Bones

• Zygomatic Bone (zī-gō-mah-tihck):

  • Forms the infraorbital rim and cheekbone.

  • Projections from the temporal bone and zygomatic bone join together to construct the zygomatic arch.

• Maxilla (mahck-sih-lah):

  • Paired bones forming the upper jaw housing upper cheek teeth.

• Mandible (mahn-dih-buhl):

  • Bone forming the lower jaw housing lower teeth.

• Palatine Bone (pahl-ah-tihn):

  • Forms the caudal portion of the hard palate.

• Lacrimal Bone (lahck-rih-mahl):

  • Forms the medial wall of the orbit (eye socket).

• Incisive Bone (ihn-sī-sihv):

  • Paired rostral bone housing upper incisor teeth and forming the lower nares margin.

• Nasal Bone (nā-sahl):

  • Forms the bridge of the nose and roof of the nasal cavity.

• Vomer Bone (vō-mər):

  • Forms the ventral base of the nasal septum.

  • Nasal Septum (nā-sahl sehp-tuhm): The central cartilaginous divider splitting the nasal cavity into left and right sides.

• Hyoid Bone (hī-oyd):

  • U-shaped apparatus suspended centrally between the mandible and the laryngopharynx, supporting the tongue and larynx.

Breed Variations in Canine Skull Conformation

• Canine skull shapes display wide variations across distinct breeds, classified into three primary structural categories:

• Brachycephalic (brä-kē-seh-fahl-ihck):

  • Characterized by short, broad, wide heads.

  • Examples: Pugs, Pekingese.

• Dolichocephalic (dō-lih-kō-seh-fahl-ihck):

  • Characterized by narrow, long, elongated head structures.

  • Examples: Collies, Greyhounds.

• Mesocephalic (mehs-ō-seh-fahl-ihck) / Mesaticephalic (mehs-at-ih-seh-fahl-ihck):

  • Characterized by average or intermediate skull width and muzzle length.

  • Example: Labrador Retrievers.

Anatomy of the Vertebral Column

• Vertebral Column (vər-teh-brahl):

  • Also designated as the spinal column or backbone.

  • Functions to support the head and trunk, transfer body weight, and enclose and protect the delicate spinal cord.

• Vertebra (vər-teh-brah):

  • An individual bony unit of the spinal column.

  • Plural: Vertebrae (vər-teh-brā).

  • Combining forms: spondyl/o, vertebr/o.

• Vertebral Structure:

  • Vertebrae are segmented into specialized functional regions.

  • The solid, heavy ventral portion of an individual vertebra is termed the body.

The Vertebral Column & Vertebral Anatomy

• General Vertebral Structure:

  • Body: The solid, ventral portion of the vertebra situated ventral to the spinal cord.

  • Arch: The dorsal part of the vertebra that arches over and surrounds the spinal cord.

  • Lamina (pronounced lahm-ih-nah): The left or right dorsal half of the vertebral arch.

  • Processes: Projections extending from the bone. Specific vertebral processes include:

    • Spinous Process: A single projection extending dorsally from the dorsal part of the vertebral arch.

    • Transverse Processes: Paired projections extending laterally from the right and left sides of the vertebral arch.

    • Articular Processes: Paired cranial and caudal projections located on the dorsum of the vertebral arch that articulate with adjacent vertebrae.

  • Foramen (pronounced fō-rā-mehn): An opening or passage through bone.

    • Vertebral Foramen: The central opening formed by the body and arch through which the spinal cord passes.

  • Intervertebral Discs: Cartilage discs that separate and cushion individual vertebrae from one another. The combining form for intervertebral discs is disc/o.

• Vertebral Regions & Naming:

  • Vertebrae are organized and named based on their anatomical location along the spinal column.

  • Cervical Region (pronounced sihr-vih-kahl): The neck area; abbreviated as "C".

  • Thoracic Region (pronounced thō-rahs-ihck): The chest area; abbreviated as "T".

  • Lumbar Region (pronounced luhm-bahr): The loin area; abbreviated as "L".

  • Sacral Region (pronounced sā-krahl): The sacrum area; abbreviated as "S".

  • Coccygeal Region (pronounced kohck-sih-jē-ahl): The tail area; also called caudal; abbreviated as "Cy" or "Cd".

• Specifically Named Vertebrae:

  • Atlas (C1): The first cervical vertebra (cervical vertebra one).

  • Axis (C2): The second cervical vertebra (cervical vertebra two).

  • Memory Tip: Atlas and Axis follow alphabetical order from cranial to caudal.

• Species-Specific Vertebral Formulas:

*   **Dogs and Cats:** $C = 7, T = 13, L = 7, S = 3, Cy = 6-23$
*   **Equine:** $C = 7, T = 18, L = 6$ (or $L = 5$ in some Arabians), $S = 5, Cy = 15-21$
*   **Bovine:** $C = 7, T = 13, L = 6, S = 5, Cy = 18-20$
*   **Pigs:** $C = 7, T = 14-15, L = 6-7, S = 4, Cy = 20-23$
*   **Sheep and Goats:** $C = 7, T = 13, L = 6-7, S = 4, Cy = 16-18$
*   **Chicken:** $C = 14, T = 7, LS = 14, Cy = 6$ (Note: Lumbar and sacral vertebrae are fused into a single unit termed $LS$)

The Thoracic Cage (Ribs & Sternum)

• Ribs (Costals):

  • Paired bones that attach dorsally to the thoracic vertebrae.

  • The combining form for rib is cost/o.

  • Ribs are also referred to as costals.

• Sternum (Breastbone):

  • Pronounced stər-nuhm.

  • Forms the midline ventral portion of the rib cage.

  • Divided into three distinct anatomical parts from cranial to caudal:

    1. Manubrium (pronounced mah-nū-brē-uhm): The cranial portion of the sternum.

    2. Body: The middle portion of the sternum.

    3. Xiphoid Process (pronounced zī-foyd): The caudal portion of the sternum.

• Thoracic Cavity Boundary:

  • The boundaries of the thoracic cavity (rib cage) are formed by the ribs, sternum, and thoracic vertebrae.

  • Function: Protects vital internal organs, specifically the heart and lungs.

The Appendicular Skeleton: Front Limb (Thoracic Limb)

• Proximal-to-Distal Sequence of Bones:

  1. Scapula

  2. Clavicle

  3. Humerus

  4. Radius & Ulna

  5. Carpus

  6. Metacarpals

  7. Phalanges

• Proximity Anatomy & Features:

  • Scapula (pronounced skahp-yoo-lah): Commonly known as the shoulder blade; a large, flat, triangular bone located on the lateral side of the thorax.

  • Clavicle (pronounced klahv-ih-kuhl): Commonly known as the collarbone; a slender bone connecting the sternum to the scapula.

    • Species Differences: Some species possess only a vestigial (pronounced vehs-tihj-ē-ahl), or rudimentary, clavicle. Other species, including equine, swine, and ruminants, completely lack a clavicle.

  • Humerus (pronounced hū-mər-uhs): The long bone of the proximal front limb. This anatomical region is sometimes called the brachium (pronounced brā-kē-uhm).

• Forearm (Antebrachium):

  • The region formed by the radius and ulna is called the antebrachium (pronounced ahn-tih-brā-kē-uhm); the prefix ante- means "before".

  • Radius (pronounced rā-dē-uhs): The cranial bone of the forearm.

  • Ulna (pronounced uhl-nah): The caudal bone of the forearm.

    • Olecranon (pronounced ō-lehck-rah-nohn): A proximal projection of the ulna that forms the point of the elbow.

    • Fusion Note: In certain species, the radius and ulna are fused together.

• Carpus & Metacarpals:

  • Carpal Bones (pronounced kahr-pahl): Irregularly shaped bones corresponding to the human wrist.

    • In small animals, this joint is referred to as the carpus.

    • In large animals, this joint is commonly called the knee.

  • Metacarpals (pronounced meht-ah-kahr-pahlz): Bones located distal to the carpus (the prefix meta- means "beyond").

    • Metacarpals are identified numerically from medial to lateral (starting with digit I medially).

• Comparative Equine & Ruminant Metacarpals:

  • Equine Adaptation:

    • Metacarpals II and IV do not articulate with the phalanges and are commonly called splint bones.

    • Splint bones are attached via an interosseous (pronounced ihn-tər-ohs-ē-uhs) ligament to the large third metacarpal bone.

    • Metacarpal III is commonly called the cannon bone.

  • Ruminant Adaptation:

    • In ruminants, the cannon bones are composed of metacarpal (and metatarsal) bones III and IV.

The Appendicular Skeleton: Rear Limb (Pelvic Limb)

• Pelvis (Hip):

  • Pronounced pehl-vihs.

  • Consists of three paired bones that fuse together:

    1. Ilium (pronounced ihl-ē-uhm): The largest, blade-shaped, cranial pair of bones. Articulates with the sacrum to form the sacroiliac joint (pronounced sā-krō-ihl-ē-ahck).

    2. Ischium (pronounced ihs-kē-uhm): The caudal pair of pelvic bones.

    3. Pubis (pronounced pehwb-ihs): The ventral pair of pelvic bones, joined at the midline by a cartilaginous joint called the pubic symphysis (pronounced pehwb-ihck sihm-fih-sihs).

  • Acetabulum (pronounced ahs-eh-tahb-yoo-luhm): The large concave socket formed where the ilium, ischium, and pubis meet. It forms a ball-and-socket joint with the head of the femur.

• Pelvic Terminology & Memory Aids:

  • Cranial to Caudal Order: Ilium precedes Ischium alphabetically from cranial to caudal.

  • Cattle Landmarks: The prominence of the ilium is called the hook, and the prominence of the ischium is called the pin (hooks and pins also follow cranial-to-caudal alphabetical order).

  • Sound-Alike Clarification: Ileum vs. Ilium

    • Ileum (with an "e"): Distal or aboral portion of the small intestine (associated with eating and enter/o).

    • Ilium (with an "i"): Bone of the pelvis (both ilium and pelvis contain an "i").

• Femur (Thigh Bone):

*   Pronounced *fē-muhr*.
*   The proximal long bone of the rear limb.
*   **Femoral Head** (pronounced *fehm-ohr-ahl*): The smooth, rounded proximal end that articulates with the acetabulum.
*   **Femoral Neck:** The narrow region connecting the head to the shaft of the femur.
*   **Trochanters** (pronounced *trō-kahn-tehrs*): Large, flat, broad projections on the femur for muscle attachment.
*   **Condyles** (pronounced *kohn-dīlz*): Rounded articular projections located at the distal end of the femur.

• Stifle Joint & Patella:

  • Patella (pronounced pah-tehl-ah): A large sesamoid bone in the rear limb (termed the kneecap in humans).

  • Stifle Joint (pronounced stī-fuhl): The joint between the femur and tibia/fibula that houses the patella.

  • Terminology Warning ("Knee Deep in Trouble"): Using the term "knee" for the stifle joint is anatomically inaccurate in veterinary medicine. Laypeople may call the stifle of dogs and cats a knee, but in veterinary terminology, "knee" is reserved for the carpal joint of large animals.

  • Popliteal Sesamoid (pronounced pohp-liht-ē-ahl): An additional sesamoid bone found on the caudal surface of the stifle joint in certain animals.

• Lower Rear Leg & Tarsus:

  • Crus (pronounced kruhs): The anatomical area of the rear limb located between the stifle and the hock.

  • Tibia (pronounced tihb-ē-ah): The larger, cranial, primary weight-bearing bone of the lower rear leg.

  • Fibula (pronounced fihb-yoo-lah): The long, slender, caudal bone of the lower rear leg. In some species, it does not extend to the distal end or is completely fused to the tibia.

  • Tarsus / Hock:

    • Tarsal Bones (pronounced tahr-suhs): Irregularly shaped bones corresponding to the human ankle.

    • Called the tarsus in small animals and the hock (pronounced hohck) in large animals.

    • Talus (pronounced tahl-uhs): The shorter, medial tarsal bone located in the proximal row (Talus and Tarsus both start with t).

    • Calcaneus (pronounced kahl-kā-nē-uhs): The long, lateral tarsal bone in the proximal row that forms the point of the hock. Named because it resembles a piece of chalk (calcium). (Calcaneus and Carpus both start with c, but calcaneus is located in the hindlimb).

  • Metatarsals: Bones distal to the tarsus; numbered and structured similarly to the metacarpals of the front limb.

Digits, Phalanges, & Comparative Foot Anatomy

• Phalanges & Digit Anatomy:

  • Phalanges (pronounced fā-lahn-jēz; singular: phalan): The individual bones that compose a digit.

  • Numbering System:

    • Digits are numbered medially to laterally using Roman numerals ($\text{I}$, $\text{II}$, $\text{III}$, $\text{IV}$, $\text{V}$).

    • Phalanges are numbered proximally to distally ($\text{P1}$, $\text{P2}$, $\text{P3}$).

  • Most digits possess three phalanges ($\text{P1}$ = proximal, $\text{P2}$ = medial, $\text{P3}$ = distal).

  • The most medial digit (Digit $\text{I}$) possesses only two phalanges.

• Species Differences in Digits:

  • Dogs & Cats: Digit $I$ on the front limb is called the dewclaw and is frequently surgically removed shortly after birth.

  • Ungulates (pronounced uhng-yoo-lātz): Animals possessing hooves.

  • Cloven-Hoofed Animals (e.g., ruminants, swine):

    • Possess functional Digits $III$ and $IV$, with three phalanges each; $P3$ is encased entirely within the hoof.

    • Digits $II$ and $V$ are vestigial and are also called dewclaws.

  • Equine Species:

    • Possess only a single functional digit per limb (Digit $III$), containing three phalanges ($P1$, $P2$, and $P3$).

• Livestock Joint & Bone Terminology:

  • Joint Names:

    • Fetlock Joint: The joint between metacarpal/metatarsal $III$ and the proximal phalanx ($P1$).

    • Pastern Joint: The joint between $P1$ and $P2$.

    • Coffin Joint: The joint between $P2$ and $P3$.

  • Bone Names:

    • Long Pastern Bone: Common name for $P1$.

    • Short Pastern Bone: Common name for $P2$.

    • Coffin Bone: Common name for $P3$.

• Claws & Surgical Terminology:

  • In non-hooved animals, $P3$ is commonly called a claw.

  • The combining form for claw is onych/o.

  • Onychectomy (pronounced ohn-ih-kehk-tō-mē): The formal medical term for surgical removal of claws (declawing) in cats.

• Sesamoid Bones:

  • Sesamoid Bones (pronounced sehs-ah-moyd): Small, nodular bones embedded within a tendon or joint capsule.

  • Navicular Bone: The common name for the specific distal sesamoid bone located inside the equine hoof on the palmar or plantar surface of $P3$.

Structural Support and Bone Features

Bones are not structurally smooth; they frequently feature bumps, grooves, ridges, depressions, and extensions that serve specific anatomical functions. Knowing descriptive medical terms makes learning bone structures easier.

Categorization of Bone Features

• Bone Extensions: Enlargements, usually located at the ends of bones, where muscles, tendons, and other bones attach.

• Bone Depressions: Depressions in bone that allow bones to attach to each other or serve as passageways for blood vessels and nerves.

Alphabetical List of Bone Terminology

• aperture (ahp-ər-chər) = opening. (Bone Depression)

• canal (kahn-ahl) = tunnel. (Bone Depression)

• condyle (kohn-dil) = rounded projection (that articulates with another bone). (Bone Extension)

• crest (krehst) = high projection or border projection. (Bone Extension)

• crista (krihs-tah) = ridge. (Bone Extension)

• dens (dehnz) = toothlike structure. (Bone Extension)

• eminence (ehm-ih-nehns) = surface projection. (Bone Extension)

• facet (fahs-eht) = smooth area. (Bone Extension)

• fissure (fihz-uhr) = deep cleft. (Bone Depression)

• foramen (fō-rä-mehn) = hole. (Bone Depression)

• fossa (fohs-ah) = trench or hollow depressed area. (Bone Depression)

• fovea (fō-vě-ah) = small pit. (Bone Depression)

• head = major protrusion. (Bone Extension)

• lamina (lahm-ih-nah) = thin, flat plate. (Bone Extension)

• line = low projection or ridge. (Bone Extension)

• malleolus (mah-lē-ō-luhs) = rounded projection (distal end of tibia and fibula). (Bone Extension)

• meatus (mē-ā-tuhs) = passage or opening. (Bone Depression)

• process (proh-sehs) = projection. (Bone Extension)

• protuberance (prō-too-bər-ahns) = projecting part. (Bone Extension)

• ramus (rā-muhs) = branch or smaller structure given off by a larger structure. (Bone Extension)

• sinus (sīn-uhs) = space or cavity. (Bone Depression)

• spine (spīn) = sharp projection. (Bone Extension)

• sulcus (suhl-kuhs) = groove. (Bone Depression)

• suture (soo-chuhr) = seam. (Bone Extension)

• trochanter (trō-kahn-tehr) = broad, flat projection (on femur). (Bone Extension)

• trochlea (trōck-lē-ah) = pulley-shaped structure in which other structures pass or articulate. (Bone Extension)

• tubercle (too-behr-kuhl) = small, rounded surface projection. (Bone Extension)

• tuberosity (too-beh-rohs-ih-tē) = projecting part. (Bone Extension)

Specific Anatomical Examples: Humerus Surface Features

• Humerus - Cranial View Landmarks:

  • Lesser tubercle

  • Teres minor tuberosity

  • Crest of the greater

  • Greater tubercle

• Humerus - Caudal View Landmarks:

  • Greater tubercle

  • Lesser tubercle

  • Head

Diagnostic Procedures for the Skeletal System

• arthrocentesis = surgical puncture of a joint to remove fluid for analysis.

• arthrography = injection of a joint with contrast material for radiographic examination.

• arthroscopy = visual examination of the joint using a fiberoptic scope (called an arthroscope when used in the joint).

• densitometer = device that measures bone density using light and X-rays.

• goniometer = instrument that measures angles or range of motion in a joint (goni/o means angle or seed).

• radiology = study of internal body structures after exposure to ionizing radiation; used to detect fractures and diseases of bones.

Pathologic Conditions of the Skeletal System

• ankylosis = loss of joint mobility caused by disease, injury, or surgery (ankyl/o means bent or stiff).

• arthralgia = joint pain.

• arthritis = inflammatory condition of joints.

• arthrodynia = joint pain.

• arthropathy = joint disease.

• bursitis = inflammation of the bursa.

• chondromalacia = abnormal cartilage softening.

• chondroplasty = cartilage disease.

• disco spondylitis = inflammation of the intervertebral disc and vertebrae.

• epiphysis’s = inflammation of the growth plate.

• exostosis= benign growth on the bone surface.

• gouty arthritis or gout = joint inflammation associated with the formation of uric acid crystals in the joint (seen more commonly in birds).

• hip dysplasia = abnormal development of the pelvic joint causing the head of the femur and the acetabulum not to be aligned properly; most commonly seen in large breed dogs.

• intervertebral disc disease = rupture or protrusion of the cushioning disc found between the vertebrae that results in pressure on the spinal cord or spinal nerve roots; also called herniated disc, ruptured disc, or IVDD.

• kyphosis = dorsal curvature of the spine; also called hunchback.

• Legg-Calve-Perthes disease = idiopathic necrosis of the femoral head and neck of small breed dogs; also called avascular necrosis of the femoral head and neck.

• lordosis = position in which the vertebral column is abnormally curved ventrally; seen in cats in heat; commonly called swayback.

• luxation = dislocation or displacement of a bone from its joint.

• myeloma = tumor composed of cells derived from hematopoietic tissues of bone marrow.

• ostealgia = bone pain.

• osteitis = inflammation of bone.

• osteoarthritis = degenerative joint disease commonly associated with aging or wear and tear on the joints; also called degenerative joint disease, or DJD.

• osteochondrosis = degeneration or necrosis of bone and cartilage followed by regeneration or recalcification.

• osteochondrosis dissecans = degeneration or necrosis of bone and cartilage followed by regeneration or recalcification with dissecting flap of articular cartilage and some inflammatory joint changes; detached pieces of articular cartilage are called joint mice or osteophytes.

• osteomalacia = abnormal softening of bone.

• osteomyelitis = inflammation of bone and bone marrow.

• osteonecrosis = death of bone tissue.

• osteoporosis = abnormal condition of marked loss of bone density and an increase in bone porosity.

• osteosclerosis = abnormal hardening of bone.

• periostitis = inflammation of the fibrous tissue that forms the outermost covering of bone.

• rheumatoid arthritis = autoimmune disorder of the connective tissues and joints; abbreviated RA.

• sequestrum = piece of dead bone that is partially or fully detached from the adjacent healthy bone.

• spondylitis = inflammation of the vertebrae.

• spondylosis = any degenerative disorder of the vertebrae.

• spondylosis deformans = chronic degeneration of the articular processes and the development of bony outgrowths around the ventral edge of the vertebrae; an age-related change in dogs where bone spurs form that can eventually bridge between vertebrae.

• spur = bony projection growing out of a bone.

• subluxation = partial dislocation or displacement of a bone from its joint.

• synovitis = inflammation of the synovial membrane of joints.

Fracture Terminology, Interventions, and Bone Healing

Types of Fractures and Related Terms

• avulsion fracture = broken bone in which the site of muscle, tendon, or ligament insertion is detached by a forceful pull.

• callus = bulging deposit around the area of a bone fracture that may eventually become bone.

• closed fracture = broken bone in which there is no open wound in the skin; also known as a simple fracture.

• comminuted fracture = broken bone that is splintered or crushed into multiple pieces.

• compression fracture = broken bone produced when the bones are pressed together.

• crepitation = cracking sensation that is felt and heard when broken bones move together; also referred to as crepitus.

• displaced fracture = bone fracture parts are out of line.

• fracture = broken bone.

• greenstick fracture = bone that is broken only on one side and the other side is bent; also called incomplete fracture.

• oblique fracture = broken bone that has an angular break diagonal to the long axis.

• open fracture = broken bone in which there is an open wound in the skin; also known as a compound fracture.

• pathologic fracture = broken bone in an area of bone weakened by disease.

Fracture Realignment and Medical Interventions

• immobilization = act of holding, suturing, or fastening a bone in a fixed position, usually with a bandage or cast.

• manipulation = attempted realignment of the bone involved in a fracture or dislocation; also known as reduction.

Physiological Mechanism of Bone Repair

1. Hematoma Formation: When a bone is fractured, blood vessels bleed into the fracture site and form a hematoma.

2. Cellular Invasion and Matrix Production: After a few days, osteoblasts move into the area and start to produce new bone matrix.

3. Osteocyte Maturation: As the new matrix is synthesized, osteoblasts develop into osteocytes.

4. Bony Fusion: The new bone eventually fuses together the segments of the fracture.

Fracture Healing Complications

• malunion = condition in which two bony ends of the fracture fail to heal together correctly.

• nonunion = condition in which there is total failure of fracture healing.

Anatomical Features, Bone Alignment, and Fracture Classification

• Anatomical and Structural Bone Features:

  • Condyle: Round bone projection.

  • Crest: Ridge of bone.

  • Facet: Smooth joint surface.

  • Fissure: Split-like opening in a bone.

  • Fossa: Depression in a bone.

  • Pastern Joint: Joint located between the long pastern bone (first phalanx) and short pastern bone (second phalanx) / common bone.

  • Coffin Joint: Joint located between the short pastern bone and the coffin bone (distal phalanx).

  • Navicular Bone: Bone positioned directly behind the coffin joint.

  • Hock: Joint of the hind limb.

  • Stifle: Joint of the hind limb corresponding to the knee.

  • IVDD: Abbreviation for Intervertebral Disc Disease.

  • DJD: Abbreviation for Degenerative Joint Disease.

• Bone Deformity Terminology:

  • Valgus (vahl-guhs): Abnormally bending outward (laterally). Memory key: both valgus and lateral contain the letter l.

  • Varus (vahr-uhs): Abnormally bending inward (medially).

• Fracture Classifications and Definitions:

  • Avulsion fracture: Fracture in which a fragment of bone is pulled away by a tendon or ligament.

  • Greenstick fracture (incomplete fracture): Fracture in which the bone is partially broken, bent, or cracked without complete separation.

  • Physeal fracture (fi-sē-ahl): Fracture occurring at the epiphyseal line or growth plate. These fractures are categorized using the Salter-Harris I–V classification system.

  • Spiral fracture (spī-rahl): Fracture in which the bone is twisted or spiraled apart.

  • Stress fracture: Fracture caused by repetitive, localized stress on a bone.

  • Transverse fracture (trahnz-vərs): Fracture occurring straight across the bone, at right angles to its long axis.

Surgical Procedures of the Skeletal System

• Skeletal Surgical Terms and Definitions:

  • Amputation (ahmp-yoo-tā-shuhn): Removal of some or all of a body part.

  • Arthrodesis (ahr-thrō-dē-sihs): Surgical fusion of a joint or spinal vertebrae. The suffix -desis denotes binding or surgical fixation of a bone or joint.

  • Chemonucleolysis (kē-mō-nū-klē-ō-li-sihs): Process of dissolving part of the center of an intervertebral disc by injecting a foreign substance.

  • Craniotomy (krā-nē-oht-ō-mē): Surgical incision or opening into the skull.

  • External fixation: Alignment of bone maintained by immobilizing the bone near the fracture site using external appliances such as casts, splints, or external fixators (rods or pins).

  • Internal fixation: Alignment of bone maintained by immobilizing the bone directly at the fracture site using surgically attached hardware such as wires, screws, pins, or plates.

  • Laminectomy (lahm-ih-nehck-tō-mē): Surgical removal of the dorsal arch of a vertebra.

  • Onychectomy (ohn-ih-kehk-tō-mē): Surgical removal of a claw or nail.

  • Ostectomy (ohs-tehck-tō-mē): Surgical removal of bone.

  • Osteocentesis (ohs-tē-ō-sehn-tē-sihs): Surgical puncture and tapping of a bone.

  • Osteodesis (ohs-tē-ō-dē-sihs): Surgical fusion of bones.

  • Osteopexy (ohs-tē-ō-pehck-sē): Surgical fixation of a bone to the body wall.

  • Osteoplasty (ohs-tē-ō-plahs-tē): Surgical repair of bone.

  • Osteostomy (ohs-tē-ohs-tō-mē): Surgical creation of a permanent new opening in bone.

  • Osteotomy (ohs-tē-oht-ō-mē): Surgical incision or sectioning (cutting into) a bone.

  • Trephination (treh-fih-nā-shuhn): Process of cutting a hole into a bone using a trephine (trē-fīn), which is a circular sawlike instrument used to remove bone or tissue.

Veterinary Chiropractic Care and Spinal Mechanics

• Interconnected Body Systems:

  • Body systems do not work in isolation. To achieve movement (such as a horse galloping or a gerbil running in an exercise wheel), the skeletal, muscular, and nervous systems must act together to coordinate limb movements.

• Principles of Veterinary Chiropractic Care:

  • Emerging subspecialization in veterinary medicine focusing on the structure and function of the musculoskeletal and nervous systems and how their relationship impacts health.

  • Etymology: Derived from the Greek words cheir (hand) and praktike (business or practice).

  • Modalities include spinal manipulation, manual therapy, and conservative holistic techniques.

  • Objectives: Restore normal joint motion, stimulate nerve reflexes, reduce pain, and lessen abnormal muscle tone.

• Chiropractic and Spinal Terminology:

  • Adjustment (also called manipulation): Application of a controlled, rapid thrust of precise direction and depth delivered to a specific contact point.

  • Fixation: Condition in which a joint becomes immobilized in a fixed position, occurring either at rest or during normal movement.

  • Malarticulations: Connections between bones that do not line up correctly.

  • Misalignment (also called subluxation): Motion segment in which alignment, movement integrity, or physiological function is altered while joint surface contact remains intact. Vertebral misalignment interferes with nerve signals from the brain.

  • Motion segment: The basic functional unit of the spine. Consists of two adjacent articulating surfaces and the connecting tissues binding them together (including two vertebrae, the intervertebral disc, nerves, arteries, and soft tissue structures such as muscles, ligaments, and tendons).

  • Range of motion (ROM): Total amount of movement occurring at a particular joint or body region.

  • Spinal manipulation: Manipulation of the spine to restore normal motion and alignment, thereby relieving restrictions on nerves or the spinal cord that impair nervous function and organ innervation. Used primarily for animals with back or neck pain.

• Basic Movements of the Vertebral Column:

  • Extension: Ventral arching or straightening of the spine.

  • Flexion: Dorsal arching of the spine.

  • Lateral flexion: Bowing or bending to either side (right or left).

  • Rotation: Twisting to the right or left.

Muscular System Physiology, Fiber Types, and Supporting Structures

• Functions of the Muscular System:

  • Muscles contract to produce physical motion.

  • Ambulation (ahm-bū-lā-shuhn): Walking, running, or moving from place to place.

  • Involuntary movement of internal organs/tissues (e.g., gastrointestinal tract contractions moving food, or blood vessel contractions circulating fluids).

  • Heat generation to maintain body temperature.

• Cellular Structure and Combining Forms:

  • Muscle fibers: Long, slender cells encased in a fibrous sheath.

  • Primary functional characteristic: Contractibility.

  • Combining forms for muscle: my/o and myos/o.

  • Combining forms for fibrous tissue: fibr/o and fibros/o.

• Types of Muscle Tissue:

  • Skeletal Muscle:

  • Description: Striated (strī-āt-ehd), voluntary.

  • Microscopic appearance: Long, cylindrical, multinucleated cells with dark and light bands creating a striped/striated appearance.

  • Combining form for striated muscle: rhabdomy/o (rahb-dō-mī-ō).

  • Function: Attaches bones to the body to enable voluntary motion.

  • Smooth Muscle:

  • Description: Nonstriated (unstriated), involuntary, visceral.

  • Microscopic appearance: Spindle-shaped cells without stripes or striations.

  • Combining form for smooth muscle: leiomy/o (lī-ō-mī-ō).

  • Function: Produces slow contractions to enable unconscious operation of internal organs.

  • Cardiac Muscle:

  • Description: Striated, involuntary.

  • Microscopic appearance: Elongated, branched cells lying parallel to each other with dark and light bands, connected by intercalated disks.

  • Function: Involuntary contraction of heart muscle.

• Connective Tissue Support Structures:

  • Fascia (fahsh-ē-ah): Sheet of fibrous connective tissue that covers, supports, and separates muscles. Combining forms: fasci/o and fasc/i.

  • Tendon (tehn-dohn): Narrow band of connective tissue attaching muscle to bone. Combining forms: tend/o, tendin/o, and ten/o.

  • Distinction: Tendons attach muscle to bone; ligaments attach bone to bone.

  • Linea alba: Latin for "white line". A fibrous band of connective tissue on the ventral abdominal wall serving as the median attachment point for abdominal muscles.

  • Aponeurosis (ahp-ō-nū-rō-sihs; plural aponeuroses): Fibrous sheet providing attachment to muscular fibers, functioning as an origin or insertion site for flat muscles. Combining form: aponeur/o.

Kinesiology, Muscle Actions, and Naming Conventions

• Kinesiology Foundations:

  • Combining form kinesi/o and suffix -kinesis mean movement.

  • Kinesiology (kih-nē-sē-ohl-ō-jē): The study of movement.

• Neuromuscular Mechanics and Interactions:

  • Root terms: anti- (against), agon (struggle), syn- (together), erg (work).

  • Agonistic (ā-gohn-ihs-tihck) muscles: Muscles that execute a specific movement.

  • Antagonistic (ahn-tă-gohn-ihs-tihck) muscles: Pairs of muscles that work opposite or against each other (one pair moves a body part in one direction, while the opposing pair moves it in the opposite direction).

  • Synergists (sihn-ahr-jihsts): Muscles that contract simultaneously with another muscle to produce or support movement.

  • Contraction (kohn-trak-shuhn): Tightening or lessening of tension, during which the muscle becomes shorter and thicker.

  • Relaxation (rē-lak-sā-shuhn): Process in which muscle tension decreases and the muscle returns to its original shape.

  • Neuromuscular junction (nū-rō-muhs-kū-lahr): Point of contact between nerve endings and muscle cells where nerve impulses signal contraction or relaxation.

  • Tonus (tō-nuhs) / Muscle tone: Normal, balanced muscle tension. Combining form for tone, tension, or stretching: ton/o.

• Muscle Naming Conventions:

  • Origin and Insertion:

  • Muscle origin (ōr-ih-jihn): Place where a muscle begins (originates); the more fixed attachment point closest to the midline.

  • Muscle insertion (ihn-sihr-shuhn): Place where a muscle ends (inserts); the more movable attachment point farthest from the midline.

  • Example: The Brachioradialis muscle originates on the brachium (humerus) and inserts on the radius.

  • Manner of Movement (Action / ROM):

  • Abductor (ahb-duhck-tər): Moves a part away from the midline.

  • Adductor (ahd-duhck-tər): Moves a part toward the midline.

  • Flexor (flehck-sər): Bends a joint or decreases the angle of a joint.

  • Extensor (ehk-stehn-sər): Straightens a limb or joint.

  • Levator (lē-vā-tər): Raises a body part.

  • Depressor (dē-prehs-ər): Depresses or lowers a body part.

  • Rotator (rō-tā-tər): Rotates a body part on its axis.

  • Supinator (soo-pĭ-nā-tər): Turns the palmar surface upward or forward.

  • Pronator (prō-nā-tər): Turns the palmar surface downward or backward.

Muscle Naming Conventions by Action and Movement

• Adductor (ahd-duhck-tər): Muscle that moves a part toward the midline.

• Flexor (flehck-sər): Muscle that bends a limb at its joint or decreases the joint angle.

• Extensor (ehcks-tehn-sər): Muscle that straightens a limb or increases the joint angle.

• Levator (lē-vă-tər): Muscle that raises or elevates a part.

• Depressor (dē-prehs-sər): Muscle that lowers or depresses a part.

• Rotator (rō-tā-tər): Muscle that turns a body part on its axis.

• Supinator (soo-pih-nā-tər): Muscle that rotates the palmar or plantar surface upward.

• Pronator (prō-nā-tər): Muscle that rotates the palmar or plantar surface downward.

Muscle Naming Conventions by Anatomical Location and Depth

• Pectoral Muscles: Located on the chest (pector = chest).

• Epaxial Muscles (ehp-ahcks-ē-ahl): Located above the pelvic axis (epi- = above; axis = line about which rotation occurs).

• Intercostal Muscles: Located between the ribs (inter- = between; cost/o = rib).

• Infraspinatus Muscles: Located beneath the spine of the scapula (infra- = beneath or below).

• Supraspinatus Muscles: Located above the spine of the scapula (supra- = above).

• Group Position Descriptors:

  • Inferior: Below or deep.

  • Medius: Middle.

  • Superior: Above.

• Depth Descriptors:

  • Externus: Outer.

  • Internus: Inner.

• Surrounding Muscle Structures:

  • Orbicularis: Muscles surrounding another structure.

Muscle Naming Conventions by Fiber Direction

• Rectus (rehck-tuhs): Means straight; rectus muscles align with the vertical axis of the body.

• Oblique (ō-blēck): Means slanted; oblique muscles slant outward away from the midline.

• Transverse: Means crosswise; transverse muscles form crosswise to the midline.

• Sphincter: Means tight band; sphincter muscles are ringlike and constrict the opening of a passageway.

Muscle Naming Conventions by Structural Divisions and Size

• Number of Divisions or Heads:

  • Biceps (bī-sehpz): Generally have two divisions (heads); bi- means two.

  • Triceps (trī-sehpz): Generally have three divisions (heads); tri- means three.

  • Quadriceps (kwohd-rih-sehps): Generally have four divisions (heads); quadri- means four.

  • Azygous (ā-zī-guhs): Means not paired (a- means without; zygot/o means joined); describes muscles that are not paired or divided.

• Size Descriptors:

  • Minimus: Small muscle size.

  • Maximus / Vastus: Large muscle size.

  • Latissimus: Broad muscle width.

  • Longissimus / Gracilis: Narrow muscle width.

  • Major: Describes the larger part of a muscle comparison pair.

  • Minor: Describes the smaller part of a muscle comparison pair.

Muscle Naming Conventions by Shape and Descriptive Etymology

• Shape Descriptors:

  • Deltoid (dehl-toyd): Shaped like the Greek letter delta ($\Delta$).

  • Quadratus (kwohd-rā-tuhs): Square or four-sided muscle.

  • Rhomboideus (rohm-boy-dē-uhs): Diamond-shaped muscle. (A rhomboid is a four-sided figure that may have unequal adjoining sides but equal opposite sides.)

  • Scalenus (skā-lehn-uhs): Unequally three-sided muscle (Skalenos is Greek for uneven).

  • Serratus (sihr-ā-tuhs): Saw-toothed muscle (Serratus is Latin for notched).

  • Teres (tər-ēz): Cylindrical muscle (Teres is Latin for smooth and round or cylindrical).

• Etymological and Descriptive Naming ("No Rules"):

  • Sartorius (sahr-tōr-ē-uhs): One muscle of the thigh area; named because it flexes and adducts the leg of a human to that position assumed by a tailor sitting cross-legged at work (sartorius means tailor).

  • Gemellus (jeh-mehl-uhs): Named because it is a twinned muscle (gemellus means twin).

  • Gastrocnemius (gahs-trōck-nē-mē-uhs): Leg muscle that resembles the shape of the stomach (gastr/o means stomach; kneme means leg).

Diagnostic Procedures of the Muscular System

• Electromyography (ē-lehck-trō-mī-ohg-rah-fē): Process of recording the electrical activity of muscle cells near recording electrodes; abbreviated EMG.

• Electromyogram (ē-lehck-trō-mī-ō-grahm): The record of the strength of muscle contraction caused by electrical stimulation.

Pathology of the Muscular System

• Adhesion (ahd-hē-shuhn): Band of fibers that hold structures together in an abnormal fashion.

• Ataxia (ā-tahck-sē-ah): Lack of voluntary control of muscle movement, characterized as "wobbliness". The combining form tax/o means coordination or order.

• Atonic (ā-tohn-ihck): Lacking muscle tone.

• Atrophy (ah-trō-fē): Decrease in size or complete wasting of an organ, tissue, or cell.

• Dystrophy (dihs-trō-fē): Defective growth.

• Fasciitis (fahs-ē-ī-tihs): Inflammation of the sheet of fibrous connective tissue that covers, supports, and separates muscles (fascia).

• Fibroma (fī-brō-mah): Tumor composed of fully developed connective tissue; also called fibroid (fī-broyd).

• Hernia (hər-nē-ah): Protrusion of a body part through tissues that normally contain it.

• Laxity (lahcks-ih-tē): Looseness.

• Leiomyoma (lī-ō-mī-ō-mah): Benign tumor of smooth muscle.

• Leiomyositis (lī-ō-mī-ō-sī-tihs): Inflammation of smooth muscle.

• Myasthenia (mī-ahs-thē-nē-ah): Muscle weakness; the suffix -asthenia means weakness.

• Myoclonus (mī-ō-klō-nuhs): Spasm of muscle; clon/o means violent action (spasm).

• Myoma (mī-ō-mah): Benign tumor of muscle.

• Myopathy (mī-ohp-ah-thē): Abnormal condition or disease of muscle.

• Myositis (mī-ō-sī-tihs): Inflammation of voluntary muscles.

• Myotonia (mī-ō-tō-nē-ah): Delayed relaxation of a muscle after contraction.

• Rhabdomyoma (rahb-dō-mī-ō-mah): Benign tumor of striated muscle.

• Tendinitis (tehn-dih-nī-tihs): Inflammation of the band of fibrous connective tissue that connects muscle to bone.

• Tetany (teht-ahn-ē): Muscle spasms or twitching.

Procedures Performed on the Muscular System

• Myectomy (mī-ehck-tō-mē): Surgical removal of a muscle or part of a muscle.

• Myoplasty (mī-ō-plahs-tē): Surgical repair of muscle.

• Myotomy (mī-oht-ō-mē): Surgical incision into a muscle.

• Tenectomy (teh-nehck-tō-mē): Surgical removal of a part of a tendon.

• Tenotomy (teh-noht-ō-mē): Surgical division of a tendon.

Muscle Physiology and Pharmacological Factors

• Contraction and Extension: Normal muscles contract and extend when an animal moves.

• Atrophy: In disease conditions or lack of use due to pain or paralysis, muscles can atrophy.

• Hypertrophy: Overuse of muscles due to excessive exercise can cause hypertrophy, an increase in the size of an organ, tissue, or cell.

• Anabolic Steroids: Medications that have been used to build muscle; due to human abuse, they are classified as controlled substances.

Abbreviations Related to the Skeletal and Muscular Systems

• DJD: Degenerative joint disease

• EMG: Electromyography

• fx: Fracture

• IVDD: Intervertebral disc disease

• P1: Phalanx 1

• P2: Phalanx 2

• P3: Phalanx 3

• RA: Rheumatoid arthritis

• ROM: Range of motion

• TPO: Triple pelvic osteotomy