ASC 305 - Equine Anatomy Exam 2

Cardiac Muscle

Cardiac Muscle

Involuntary, Striated and Branched | Specialized and Found only in the Heart

Smooth Muscle

Involuntary and Non-Striated | Found in the Digestive Tract, Arteries/Veins, and other Body Systems (Respiratory, Reproductive, Etc)

Skeletal Muscle

Voluntary And Striated | 50% Of The Horse’s Body | What The Horse Uses For Locomotion

Stages Of Muscles

Contraction (shortening of muscle fibers) and Relaxation (return to neutral position of muscle fibers)

Components Of Muscles

• Central Fleshy and Contractile “Muscle Body”

• 2 Tendons, One at Each End of the Muscle

• Nerve to Stimulate It

• Blood Supply through an Artery and Vein

Muscles can not ----, they can only ----.

Muscles can not push, they can only pull.

Epimysium

Muscle Belly Protective Membrane

Perimysium

Fascicle Protective Membrane

Endomysium

Muscle Fiber/Cell Protective Membrane

Myofibrils

Muscle Fibers are made up of a Bunch Of…

Actin & Myosin

Two Myofilaments that actually interact to cause Contraction.

Sarcomere

A Repeating area that contains the two myofilaments (actin & myosin). Shortening of the area occurs as the myofilaments move closer together.

Flexion, Flexors

The angle of the joint is made narrower. Muscles that have the prime function of closing the angle of a joint are called “-----”.

Extension, Extensors

The angle of the joint is widened. Muscles pass over the apex of the joint, and are called “-----”.

Adduction, Adductors

Muslces draw the limb toward the mid-line of the body. Muscles are called “----”.

Abduction, Abductors

Muscles lead the limb away from the mid-line of the body. Muscles are called “-----”.

Type I Fiber (Red Endurance Muscle)

High Oxygen Usage Capacity, Slow Response Time, Low Power, Narrow Muscle Fiber Thickness, Slow Fatigue

Type IIX (White Sprint Muscle)

Low Oxygen Usage Capacity, Quick Response Time, High Power, Thick Muscle Fiber Thickness, Quick Fatigue

Type IIA (White Sprint Muscle)

Medium Oxygen Usage Capacity, Medium Response Time, Medium Power, Medium Muscle Fiber Thickness, Medium Fatigue

Aerobic

• Uses Oxygen

• Complete Glucose Breakdown

• Produces CO2 and Water

• Releases Relatively Large Amount of Energy

Anaerobic

• Does NOT Use Oxygen

• Glucose is NOT completely broken down

• Produces Lactic Acid (By-Product)

• Releases A Small Amount Of Energy

Triceps Brachii

Shoulder: Flex

Elbow: Extend

Long Head

Origination Point: Caudel surface of scapula

Lateral Head

Origination Point: Lateral side of femur

Medial Head

Origination Point: Distal medial side of the humerus

Insertion Point (the same for all): Proximal side of Electranon Tuberosity

What is this muscle? What joints does it move? Where does it originate and insert?

Superficial Digital Flexor

Knee: Flex

Lower Leg: Flex

Origination Point: Distal End Of The Humerus

Insertion Point: 4 Insertion Points (2 - Distal Of P1, 2 - Proximal of P2)

What is this muscle? What joints does it move? Where does it originate and insert? (1)

Supraspinatus

Shoulder: Extend

Origination Point: Superaspinous Fossa

Insertion Point: (1) Greater Tubrical on the Cranial Side (2) Lesser Tubrical on the Cranial Medial Side

What is this muscle? What joints does it move? Where does it originate and insert?

Brachialis

Elbow: Flex

Origination Point: Under lesser tubricale caudel medial side (goes under the deltoid tuberosity)

Insertion Point:under the medial tuberosity of radius (medial)

What is this muscle? What joints does it move? Where does it originate and insert? (1)

Intraspinatus

Shoulder: Flex

Origination Point: Infraspinous Fossa

Insertion Point: Greater Tubrical Caudal

What is this muscle? What joints does it move? Where does it originate and insert?

Flexor Carpi Ulnaris

Elbow (Minor): Extend

Knee: Flex

Origination Point: Medial Side of the humerus

Insertion Point: 2nd Metacarpal Proximal Medial End

What is this muscle? What joints does it move? Where does it originate and insert? (3)

Extensor Carpi Radialis

Elbow: Flex

Knee: Extend

Origination Point: Lateral distal side of humerus

Insertion Point: Third metacarpal at proximal dorsal surface

What is this muscle? What joints does it move? Where does it originate and insert? (1)

Deltoid

Shoulder: Flex

Origination Point: Infraspinous Fossa (on top of the infraspinatus)

Insertion Point: Deltoid Tuberosity

What is this muscle? What joints does it move? Where does it originate and insert?

Common Digital Extensor Tendon

Knee: Extend

Lower Leg: Extend

Origination Point: Elbow Joint

Insertion Point: Extensor Process of P3

What is this muscle? What joints does it move? Where does it originate and insert? (1)

Biceps Brachii

Shoulder: Extend

Elbow: Flex

Origination Point: Super Glenod Tuberitcal

Insertion Point: Medial Tuberosity

What is this muscle? What joints does it move? Where does it originate and insert?

Lateral Ulna

Elbow (Minor): Extend

Knee: Flex

Origination Point: Distal lateral side of humerus

Insertion Point: 4th Metacarpal Proximal Lateral End & Accessory Carpal

What is this muscle? What joints does it move? Where does it originate and insert? (1)

Flexor Carpi Radialis

Elbow (Minor): Extend

Knee: Flex

Origination Point: Medial distal end of the humerus

Insertion Point: 2nd Metacarpal Proximal Medial End

What is this muscle? What joints does it move? Where does it originate and insert? (2)

Lateral Digital Extensor

Knee: Extend

Lower Leg: Extend

Origination Point: Lateral Proximal End of the Radius

Insertion Point: Dorsal Surface of Long Pasturn

What is this muscle? What joints does it move? Where does it originate and insert? (2)

Subscapularis & Teres Major

What two muscles flex the shoulder?

Omotransversaius

Origination Point: Cervical Vertebrae (Transverse Processes)

Insertion Point: Lateral Side Of Humerus

What is the blue muscle and where does it originate and insert?

Brachiocephalicus

Origination Point: Temporal Bone

Insertion Point: Lateral Side Of The Humerus

What is the red muscle and where does it originate and insert?

Sternomandibularis

Origination Point: Mandible

Insertion Point: Sternum

What is the green muscle and where does it originate and insert?

Brachiocephalicus & Sternomandibularis

Which two muscles make up the jugular groove of the horse?

Brachiocephalicus & Sternomandibularis

Which of the three lower neck muscles can directly lower the head?

Sternomandibularis

Which of the lower neck muscles discussed in class move the horses’s leg by contracting?

Sternomandibaris - pull head down (both muscles)

Left Brachiocephalicus - to pull head to the left (left side muscle only) and down (both muscles)

Left Omnotransverarius - to pull neck down (both muscles) and to the left (left side muscle only)

My horse is trying to reach a carrot on the ground and to the left side of its body. Which lower neck muscles will it use to get the carrot?

Latissimus Dorsi

Shoulder: Flex

Stabilizes Dorsal/Proximal End of Scapula

Origination: Along the supraspinous ligament (thoracic & some lumbar)

Insertion: Binds with (2) Teres Major (muscle) tuberosity

What is this muscle? What is it’s purpose? Where does it originate and insert?

Longissimus Dorsi

Connects head, neck, withers, back, loin, and group together through vertebrae allowing connected movement. Pulls spine dorsally.

Origination: Sacrum/Pelvis at Multiple Locations

Insertion: Temporal Bone

What is this muscle? What is it’s purpose? Where does it originate and insert?

External and Internal Oblique Abdominal Muscles

Part of the bowstring effect. Helps to round the horses’s spine, by pulling ribs/sternum and pelvis closer together.

External

Origination: Lateral/Ventral Side of Ribs

Insertion: Coccytuberosity/Pubis/Illium

Internal

Origination: False Ribs

Insertion: Cranial Edge of Illium

What is this muscle? What is its purpose? Where does it originate and insert? (1 & 2)

Pectoral Muscles

Part of the trampoline effect. “Catch” the axial skeleton. Adduct front legs.

Origination: Sternum

Insertion: Humerus

What is this muscle? What is it’s purpose? Where does it originate and insert? (Group Of Muscles)

Psoas Minor and Iliopsoas

Help to round lumbar spine. Tilts pelvis allows horse to reach under itself further with handles. Connect spine to pelvic limb.

Psoas Minor

Origination: Ventral of T16-L2

Insertion: Ventral Surface of Illium

Illiopsoas

Origination: Ventral Side of Transverse Processes of Lumbar

Insertion: Lesser Trochanter Lateral Side Of Femur

What is this muscle? What is it’s purpose? Where does it originate and insert? (Two Muscles)

Serratus Ventralis

Part of the trampoline effect. Contract to pull axial skeleton up towards the dorsal surface.

(1) Origination: The transverse & cervical verterbrae

(2) Origination:

Both Insert in the the medial side of the scapula

What is this muscle? What is it’s purpose? Where does it originate and insert? (1&2)

Spinalis

Connects thoracic and lumbar vertebrae and supports/stabilizes their spinous processes. Pulls vertebrae dorsally when contracts.

Origination: Sacrum/Pelvis Multiple

Insertion: Temporal Bone

What is this muscle? What is it’s purpose? Where does it originate and insert?

Trapezius

Cervical (Cranial) Portion - Rotate scapula forward (extending shoulder joint). Pulls scapula dorsally.

Origination: The Nuchal Ligament

Insertion: Cranial Part of the Spine of Scapula

Thoracic (Caudal) Portion - Rotate scapula backwards (flexing shoulder joint). Pulls scapula dorsally.

Origination: Supraspinous Ligament

Insertion: Caudal Part of the Spina of Scapula

What is this muscle? What is it’s purpose? Where does it originate and insert?

Rectus Abdominus

Part of the bowstring effect. Helps round spine through connection to sternum, ribs, and pelvis.

Origination: Ventral Surface of the First Couple True Ribs

Insertion: Pelvis, Cranial/Ventral Surface

What is this muscle? What is it’s purpose? Where does it originate and insert? (1)

The bowstring effect is when muscles along the dorsal surface of the horse’s body are balanced by abdominal muscles to allow slight rounding of the spine so that the horse can fully extend its hind legs under its body. Muscles involved are the Spinalis, Longissimus doors, Internal oblique abdominal muscle, external oblique abdominal muscles, and rectus abdominus.

What is the bowstring effect? What muscles are involved?

Catch - Pectoral Muscles

Spring Up - Serratus Ventralis

With every step, the horses’s axial skeleton acts like a trampoline between the front legs. What muscles “catch” the axial skeleton? What muscles “spring up” the axial skeleton with each step?

The thoracic sling is a combination of muscles, tendons, and ligaments that connect the thoracic skeleton to the axial skeleton. It is needed because horses do not have a joint connecting their thoracic limb to their axial skeleton (no collarbone). Pectorals, Serratus Ventralis, Trapezius, Rhombiodius, Latissimus doors are examples of muscles that are part of the thoracic sling.

What is the thoracic sling? Why is it needed?

1. Latissimus Dorsi

2. Longissimus Dorsi

3. Spinalis

4. Trapezius (Thoracic Portion)

List four back/neck muscles that could be negatively affected by poor saddle fit.

• Serratus Ventralis

• Subscapularis

• Infraspinatus

• Deltoid

• Trapezius

List these muscles from deepest to most superficial: Deltoid, Infraspinatus, Trapezius, Ventralis, Subscapularis

• Interspinous Ligaments

• Spinalis

• Longissimus dorsi

• Latissimus dorsi

• Tapezius

List these muscles from deepest to most superficial: Longissimus dorsi, Tapezius, Spinalis, Latissimus dorsi, Interspinous Ligaments

Common Digital Extensor Muscle

Lower Leg: Extends

Tarsus: Flexes

Origination: Cranial, Proximal, Lateral end of the Tibia

Insertion: Extensor Process of P3

What is this muscle? What joints does it move? Where does it originate and insert? (2)

Peroneus Tertius

Stifle & Hock (Flexes)

Part of the Reciprocal Apparatus. Connects the stifle and hock in the hind leg. When one extends, so does the other (this occurs due to interactions with the SSDF muscle/tendon).

Origination: Lateral Condyle of Femur

Insertion: Dorsal Surface of 3rd Metatarsal AND Deep Within Cranial Hock Bones

What is this muscle? What joints does it move? Where does it originate and insert? (1)

Biceps Femoris

Hip & Stifle (and hock via reciprocal apparatus)

Extends the hip and stifle (and therefore the hock). Abducts the hind limb.

Origination: Lateral Side of Sacral Vertebrae & Ischiatic Tuberosity

Insertion: Fascia

What is this muscle? What joints does it move? Where does it originate and insert?

Quadriceps Femoris

Stifle (and indirectly hock, through reciprocal apparatus) extends. Minor effect on hip flexes.

Origination: Cranial End of Pelvis & Cranial End of Femur

Insertion: Cranial Proximal End of Tibia

What is this muscle? What joints does it move? Where does it originate and insert?

Semitendinosus & Semimembranosus

Hip, Stifle, and Hock

Weight Baring: Extends the hip, stifle, and hock

Non Weight Baring: Flexes the stifle, hock

Adduction of the Hind Leg

Semitendinosus

Origination: Sacrum & Ischiatic Tuberosity

Insertion: Medial, Cranial, Proximal End of the Tibia & Fascia

Semimembranosus

Origination: Ischiatic Tuberosity

Insertion: Medial, Cranial, Proximal End of the Tibia & Fascia

What is this muscle? What joints does it move? Where does it originate and insert?

Superficial Digital Flexor Muscle/Tendon

Stifle, Hock, and Lower Leg

Connects the stifle, hock, fetlock, and pastern joints in the hind leg.

Without pernoneus teritius this muscle would flex the stifle, extend the hock, and flex the lower leg.

Reality: Works with the peroneus tertius as part of the reciprocal apparatus

Origination: Intercondylar Fossa of Femur

Insertion: Calcaneus + Distal End of P2 (2 points) Proximal End of P2 (2 points) Four Total Insertion Points

What is this muscle? What joints does it move? Where does it originate and insert? (1)

Reciprocal Apparatus

Connection of Stifle and Hock

• One Flexes, So Does The Other

• One Extends, So Does The Other

Fascia

Normal Purpose?

• Allows Muscles To Slide With Minimal Friction

• Can Stretch

How is Fascia used differently in the hind leg?

• Superficial Layer: Encloses entirety of muscles in that area

• Deeper Layer: Wrap individual muscles or muscle groups

ALSO provides an insertion point. for powerful muscles of the hindquarters.

• Pectineus

• Adductor

• Gracilis

• Sartorius

What are the hind muscles that cause adduction?

Muscle

Tendons connect ----- to bone.

Spinalis

What muscle is positioned between the longissimus dorsi and the spinous process of the thoracic vertebrae?

False

The Deltoid, Triceps Brachii, and Biceps Brachia cause extension in the shoulder joint. True or False?

Supraspinous Fossa

The supraspinatus muscle originates in the -----.

True

Both the supraspinatus and infraspinatus abduct the horse’s leg. True or False?

False

Both the supraspinatus and infraspinatus insert into the lesser tubercle. True or False?

The Infraspinous Fossa

The Deltoid originates in -----.

False

The extensor carpi radialis inserts into the accessory bone. True or False?

False

Ligaments cause movement with the assistance of muscles. True or False?

False

Tendons are able to both push and pull. True or False?

Fascia

Thin layers of connective tissue that cover board areas of muscles are called -----.

P3

The deep digital flexor tendon attaches to -----.

False

Lower leg flexor tendons can be found on the cranial/dorsal, lateral surface of the leg. True or False?

Thoracic Sling

The series of muscles that attach the front limb to the axial skeleton is called the -----.

Ventral Longitudinal

The ----- ligament keeps the ventral surface of the vertebrae equidistant to one-another.

False

Muscles can push and pull. True or False?

False

Skeletal muscles are involuntary and striated.

Mineral Storage

Which of the following is NOT a function of skeletal muscle?

• Produce Heat By Shivering

• Move Skeleton

• Mineral Storage

• Support Skeleton

Draw In Towards The Midline

Adduction means to….

Type I

Which of the following are “slow-twitch” muscle fibers?

• Type IIA

• Type I

• Type IIX

Releases Large Amounts Of Energy

Which of these is TRUE of aerobic exercise?

• Releases Large Amounts Of Energy

• Glucose Not Fully Broken Down

• Releases A Small Amount Of Energy

• Does Not Use Oxygen

True

Lactic Acid is produced by anaerobic exercise. True or False?

Brachialis

The muscle that wraps around the humerus is the…

False

The deltoid attaches to the trees major tuberosity. True or False?

False

The lateral digital extensor tendon is positioned directly next to the deep digital flexor tendon on the lateral side. True and False?

Brachiocephalicus

The ----- forms the supper portion of the jugular groove.

True

The rhomboideus pulls the neck up. True or False?

True

The trapezius can cause the scapula to swing back and forth depending on what portion is contracting. True or False?

Serratus Ventralis

Which of the following is part of the thoracic sling?

• Deltoid

• Superficial Digital Flexor Tendon

• Serratus Ventralis

• Subscapular Membranosis

True

Pectoral muscles help “catch” downward motion of the axial skeleton. True or False?

Psoas Minor & Iliopsoas

What muscles(s) that connect the pelvis to the ventral surface of the lumbar (and caudal thoracic) vertebrae are the…

Hollow

The weight of a rider will naturally ----- the back of a horse.

External & Internal Abdominal Oblique

Which of the following helps prevent the spine from becoming too hollow?

Extends

The biceps femurs ----- the hip and stifle.