Muscular System

Introduction

• Primary function is to contract– Secondary functions: movement, stabilizing body

position, regulating organ volume, generating heat, moving food &fluids through various body systems.

• Scientific study of muscles: Myology

3 Types of Muscle Tissue

• Skeletal: voluntary, striations• Cardiac: involuntary, intercalated discs• Smooth: involuntary, no striations

– We will be focusing on skeletal muscle tissue over the next few weeks

General Features of Skeletal Muscles

– Sternomastoid» Origin – manubrium» Insertion – temporal bone and nuchal crest» Action – turn/bend head» This muscle appears as two wide straps that form a ‘V’ caudal to

the transverse jugular vein.– Sternohyoid

» Origin – first costal cartilage of the sternum» Insertion – hyoid bone» Action – pull the hyoid and tongue caudally» This pair of muscles connect together along the midline just

superficial to the trachea– Digastric

» Origin – occipital and temporal bones» Insertion – mandible» Action – open mouth» This thin muscle is found adjacent to the inner mandible. Its

fibers run oblique to the midline.– Mylohyoid

» Action – raise the floor of the mouth» Found bridging the two sides of the mandible or in the

intermandibular space. Its fibers are transverse to the midline.– Masseter

» Origin – zygomatic arch» Insertion – mandible» Action – close the jaw» This cheek muscle is found cranial to the parotid salivary glands * Use the jugular vein as a

landmark for the separation of the mylohyoid and

sternohyoid

Transverse Jugular vein

Superficial Muscles of the Chest – Clean the fascia from one side of the chest. We will

dissect one side of the chest only unless a mistake is made.

– For all superficial chest muscles» Action – adduct the forelimb medially

– Pectoantebrachialis» Origin – manubrium» Insertion – forearm» Most cranial and superficial pectoral chest

muscle that spans across the chest to the elbows of the forelimbs. It is a thin strap-like shaped muscle.

» Not found in humans– Pectoralis major

» Origin – sternum» Insertion – humerus» This muscle is deep and caudal to the

pectoantebrachialis. – Pectoralis minor

» Origin – Sternum» Insertion – proximal humerus» Found caudal to pectoralis major and is larger

than the pectoralis major in the cat. The naming again is based on the human musculature.

– Xiphihumeralis» Origin – xiphoid process» Insertion – humerus» Found caudal to pectoralis minor» Not found in humans

Muscles Day 2I)Serratus ventralis

(1)Origin – transverse process of caudal cervical vertebrae and first several ribs(2)Insertion – Scapula(3)Action – pull scapula forward and down(4)Large fan shaped muscle overlaying muscles

II)External intercostals(1)Action – lift ribs during inspiration(2)Found deep to Serratus ventralis and run craniodorsal to caudoventral between the ribs

III)Internal intercostals(1)Action – depress ribs during expiration(2)Do not dissect to find these muscles but know they are found deep to external intercostals between the ribs

Deep Chest Muscles: * Use the side of the cat opposite your superficial dissection