BIO100 Chptr 9 Muscular System Flashcards
calat-
calat-,
something inserted: intercalated disc—membranous band that connects cardiac muscle cells.
erg-
erg-, work: synergist
—muscle that works with a prime mover, producing a movement.
fasc-
fasc-, bundle: fasciculus
—bundle of muscle fibers.
-gram
-gram, something written: myogram
—recording of a muscular contraction.
hyper-
hyper-, over, more: muscular hypertrophy
—enlargement of muscle fibers.
inter-
inter-, between: intercalated disc
—membranous band that connects cardiac muscle cells.
iso-
iso-, equal: isotonic contraction
—contraction during which the tension in a muscle remains unchanged.
laten-
laten-, hidden: latent period
—period between a stimulus and the beginning of a muscle contraction.
-lemm
-lemm [rind or peel] sarcolemma:
the cell membrane of a muscle fiber.
myo-
myo-, muscle: myofibril
—contractile bundle of filaments within a muscle cell.
reticul-
reticul-, a net: sarcoplasmic reticulum
—network of membranous channels within a muscle fiber.
sarco-
sarco-, flesh: sarcoplasm
—substance (cytoplasm) within a muscle fiber.
syn-
syn-, together: synergist
—muscle that works with a prime mover, producing a movement.
tetan-
tetan-, stiff: tetanic contraction
—sustained muscular contraction.
-tonic
-tonic, stretched: isotonic contraction
—contraction during which the tension of a muscle remains unchanged.
-troph
-troph, well fed/(trophy)nourishment: muscular hypertrophy
—enlargement of muscle fibers.
voluntar-
voluntar-, of one’s free will: voluntary muscle
—muscle that can be controlled by conscious effort.
fascia
Layers of connective tissue enclose and separate all parts of a skeletal muscle. An individual skeletal muscle is separated from adjacent muscles and held in position by layers of dense connective tissue called fascia
tendon
a flexible but inelastic cord of strong fibrous collagen tissue attaching a muscle to a bone.
aponeuroses
a sheet of pearly white fibrous tissue that takes the place of a tendon in flat muscles having a wide area of attachment.
fascicles
a bundle of structures, such as nerve or muscle fibers or conducting vessels in plants.
epimysium
a sheath of fibrous elastic tissue surrounding a muscle.
perimysium
the sheath of connective tissue surrounding a bundle of muscle fibers.
difference of perimysium and epimysium
The perimysium is what surrounds groups of muscle fibers to form fascicle. The epimysium surrounds a collection of fascicles that comprise the muscle. The epimysium is the outermost skeletal muscle covering.
compartment
Compartment (anatomy), a space of connective tissue between muscles.
deep fascia
a layer of dense connective tissue that can surround individual muscles and groups of muscles to separate into fascial compartments. This fibrous connective tissue interpenetrates and surrounds the muscles, bones, nerves, and blood vessels of the body.
subcutaneous fascia
also known as the hypodermis or superficial fascia, is the layer of tissue that underlies the skin.
sarcolemma
the fine transparent tubular sheath which envelops the fibers of skeletal muscles.
cytoplasm
the material or protoplasm within a living cell, excluding the nucleus.
myofibrils
any of the elongated contractile threads found in striated muscle cells.
myosin
a fibrous protein that forms (together with actin) the contractile filaments of muscle cells and is also involved in motion in other types of cells.
actin
a protein that forms (together with myosin) the contractile filaments of muscle cells, and is also involved in motion in other types of cells.
troponin
Troponins are a group of proteins found in skeletal and heart (cardiac) muscle fibers that regulate muscular contraction.
tropomyosin
a protein involved in muscle contraction. It is related to myosin and occurs together with troponin in the thin filaments of muscle tissue.
Muscle Structures*
*Structures in order of increasing complexity- Thick and thin filaments Myofibril Muscle fiber Fascicle Muscle
titin
also known as connectin, is a protein that is encoded by the TTN gene in humans. Titin is a giant protein, greater than 1 µm in length, that functions as a molecular spring which is responsible for the passive elasticity of muscle in addition to keeping myosin molecules in place.
sarcoplasmic reticulum (SR)
is a membrane-bound structure found within muscle cells that is similar to the endoplasmic reticulum in other cells. The main function of the SR is to store calcium ions (Ca2+).
transverse tubules (T tubules)
are extensions of the cell membrane that penetrate into the centre of skeletal and cardiac muscle cells. Through these mechanisms, T-tubules allow heart muscle cells to contract more forcefully by synchronizing calcium release throughout the cell.
cisternae
A cisterna (plural cisternae) is a flattened membrane disk of the endoplasmic reticulum and Golgi apparatus. A Golgi stack may contain anywhere from three to twenty cisternae, but most contain about six cisternae. Golgi cisternae can be separated into four classes; cis, medial, trans, and TGN (trans-Golgi network).
A muscle fiber contraction
is a complex interaction of several cellular and chemical constituents. The result is a movement within the myofibrils in which the filaments of actin and myosin slide past one another, shortening the sarcomeres.
synapse
Each cell that a neuron controls is connected functionally (but not physically) to the end of an axon, in much the same way that you can talk into a cell phone although your mouth is not in direct physical contact with it. The site of this functional connection is called a synapse.
neurotransmitters
Neurons communicate with the cells that they control by releasing chemicals, called neurotransmitters (nu″ro-trans-mit-erz), at a synapse.
motor neurons.
a nerve cell forming part of a pathway along which impulses pass from the brain or spinal cord to a muscle or gland.
neuromuscular junction (myoneural junction)
is a chemical synapse between a motor neuron and a muscle fiber. It allow the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. Muscles require innervation to function—and even just to maintain muscle tone, avoiding atrophy.
motor end plate
are specialised chemical synapses formed at the sites where the terminal branches of the axon of a motor neuron contact a target muscle cell.
synaptic cleft
A small gap called the synaptic cleft separates the membrane of the neuron and the membrane of the muscle fiber.
Acetylcholine (ACh)
is the neurotransmitter that motor neurons use to control skeletal muscle contraction. ACh is synthesized in the cytoplasm of the motor neuron and is stored in synaptic vesicles near the distal end of its axon.
excitation-contraction coupling
is the process by which an electrical stimulus triggers the release of calcium by the sarcoplasmic reticulum, initiating the mechanism of muscle contraction by sarcomere shortening.
Clostridium botulinum
in an anaerobic (oxygen-poor) environment, such as in a can of improperly preserved food, it produces a toxin. If a person ingests the toxin, the release of acetylcholine from axon terminals at neuromuscular junctions is prevented. Symptoms of such food poisoning include nausea, vomiting, and diarrhea; headache, dizziness, and blurred or double vision; and finally, weakness, hoarseness, and difficulty swallowing and, eventually, inability to breathe.
myasthenia gravis (MG) “grave muscular weakness”
The body produces antibodies that target receptors for the neurotransmitter acetylcholine on skeletal muscle cells at neuromuscular junctions. People with MG have one-third the normal number of acetylcholine receptors on their skeletal muscle cells. On a whole-body level, this causes weak and easily fatigued muscles.
acetylcholinesterase (AChE)
also known as AChE or acetylhydrolase, is the primary cholinesterase in the body. It is an enzyme that catalyzes the breakdown of acetylcholine and of some other choline esters that function as neurotransmitters.
creatine phosphate (PCr)
is a phosphorylated creatine molecule that serves as a rapidly mobilizable reserve of high-energy phosphates in skeletal muscle, myocard and the brain to recycle adenosine triphosphate, the energy currency of the cell.
myoglobin
a red protein containing heme, which carries and stores oxygen in muscle cells. It is structurally similar to a subunit of hemoglobin. (heme-an iron-containing compound)
lactic acid threshold
Lactate threshold is defined as the intensity of exercise at which lactate begins to accumulate in the blood at a faster rate than it can be removed.
oxygen debt,
or excess post-exercise oxygen consumption (EPOC)
is the amount of oxygen required to restore your body to its normal, resting level of metabolic function (called homeostasis).
anaerobic exercise
is any activity that breaks down glucose for energy without using oxygen. Generally, these activities are of short length with high intensity. The idea is that a lot of energy is released within a small period of time, and your oxygen demand surpasses the oxygen supply.
fatigue / Muscle (MM) fatigue
is a symptom that decreases your muscles’ ability to perform over time. It can be associated with a state of exhaustion, often following strenuous activity or exercise. When you experience fatigue, the force behind your muscles’ movements decrease, causing you to feel weaker.
cellular respiration / MM heat production
All active cells generate heat, which is a by-product of cellular respiration. Muscle tissue constitutes such a large proportion of total body mass that it is a major source of heat.
threshold stimulus
is the weakest stimulus that could generate an action potential in a neuron.
twitch
The contractile response of a single muscle fiber to a single impulse is called a twitch. A twitch consists of a period of contraction, during which the fiber pulls at its attachments, followed by a period of relaxation, during which the pulling force declines.
summation
Twitch summation or treppe is the addition of a second twitch, resulting in greater tension, and it results from stimulating the muscle before it has a chance to relax completely.
tetany
Tetany or tetanic seizure is a medical sign consisting of the involuntary contraction of muscles, which may be caused by disorders that increase the action potential frequency of muscle cells or the nerves that innervate them.
recruitment
Motor unit recruitment refers to the activation of additional motor units to accomplish an increase in contractile strength in a muscle. A motor unit consists of one motor neuron and all of the muscle fibers it stimulates.
The higher the recruitment the stronger the muscle contraction will be.
muscle tone (tonus)
is the continuous and passive partial contraction of the muscles, or the muscle’s resistance to passive stretch during resting state. It helps to maintain posture and declines during REM sleep.
concentric contraction
is a type of muscle activation that causes tension on your muscle as it shortens. As your muscle shortens, it generates enough force to move an object. This is the most popular type of muscle contraction. In weight training, a bicep curl is an easy-to-recognize concentric movement.
eccentric contraction
occurs when the total length of the muscle increases as tension is produced. For example, the lowering phase of a biceps curl constitutes an eccentric contraction. Muscles are capable of generating greater forces under eccentric conditions than under either isometric or concentric contractions.
isometric contractions (equal length—change in force)
generate force by changing the length of the muscle and can be concentric contractions or eccentric contractions. A concentric contraction causes muscles to shorten, thereby generating force.
Isometric contractions generate force without changing the length of the muscle.
multiunit smooth muscle
in the walls of the viscera, called visceral muscle, has a stress-relaxation response that permits muscle to stretch, contract, and relax as the organ expands. Multiunit smooth muscle cells do not possess gap junctions, and contraction does not spread from one cell to the next.
Visceral smooth muscle (single-unit smooth muscle)
Single-unit smooth muscle, or visceral smooth muscle is a type of smooth muscle found in the uterus, gastro-intestinal tract, and the bladder. In SUVSM, a single smooth muscle cell in a bundle is innervated by an autonomic nerve fiber.
rhythmicity
a pattern of spontaneous repeated contractions.
peristalsis
the involuntary constriction and relaxation of the muscles of the intestine or another canal, creating wave-like movements that push the contents of the canal forward.
Peripheral Resistance
is the resistance of the arteries to blood flow. As the arteries constrict, the resistance increases and as they dilate, resistance decreases. Peripheral resistance is determined by three factors: Autonomic activity: sympathetic activity constricts peripheral arteries.
calmodulin
(CaM) (an abbreviation for calcium-modulated protein) is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the binding of Ca2+ is required for the activation of calmodulin.
norepinephrine
is a naturally occurring chemical in the body that acts as both a stress hormone and neurotransmitter (a substance that sends signals between nerve cells). It’s released into the blood as a stress hormone when the brain perceives that a stressful event has occurred.
Cardiac muscle also known as myocardiocytes
Cardiac muscle tissue is a specialized, organized type of tissue that only exists in the heart. It is responsible for keeping the heart pumping and blood circulating around the body. Cardiac muscle tissue, or myocardium, contains cells that expand and contract in response to electrical impulses from the nervous system
syncytium
BIOLOGY
a single cell or cytoplasmic mass containing several nuclei, formed by fusion of cells or by division of nuclei.
EMBRYOLOGY
syncytium forming the outermost layer of the trophoblast.
intercalated discs
are unique structural formations found between the myocardial cells of the heart. They play vital roles in bonding cardiac muscle cells together and in transmitting signals between cells.
Whenever limbs or other body parts move, bones and muscles interact as simple mechanical devices called -
levers
origin of the muscle
The origin is the attachment site that doesn’t move during contraction,
insertion of the muscle
insertion is the attachment site that DOES move when the muscle contracts.
agonist
causes an action
antagonist
works against the action
prime mover
refers to an agonist that provides most of the force for a movement when more than one muscle contributes to that movement.
synergists
other muscles, called synergists, contribute to an action by helping the agonist
pectoralis major
A large (major) muscle in the pectoral region (chest).
deltoid
Shaped like a delta or triangle.
extensor digitorum
Extends the digits (fingers or toes).
biceps brachii
A muscle with two heads (biceps), or points of origin, in the brachium (arm). sternocleidomastoid Attached to the sternum, clavicle, and mastoid process.
external oblique
Located near the outside, with fibers that run obliquely or in a slanting direction.
Muscles of Facial Expression
Epicranius Zygomaticus major Orbicularis oculi Zygomaticus minor Orbicularis oris Platysma Buccinator -cheek
epicranius
covers the upper part of the cranium and includes two muscular part
the frontalis
which lies over the frontal bone
occipitalis
which lies over the occipital bone.
epicranial aponeurosis
is an aponeurosis (a tough layer of dense fibrous tissue) which covers the upper part of the cranium in humans and various other animals.
orbicularis oculi
The orbicularis oculi is a muscle in the face that closes the eyelids. It arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short fibrous band, the medial palpebral ligament.
sphincter muscle
circular muscle that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning. Sphincters are found in many animals.
lacrimal gland
are paired, almond-shaped exocrine glands, one for each eye, that secrete the aqueous layer of the tear film. They are situated in the upper lateral region of each orbit, in the lacrimal fossa of the orbit formed by the frontal bone.
orbicularis oris
muscle is a complex of muscles in the lips that encircles the mouth. It is a sphincter, or circular muscle, but it is actually composed of four independent quadrants that interlace and give only an appearance of circularity.
buccinator
is located in the wall of the cheek. Its fibers are directed forward from the bones of the jaws to the angle of the mouth, and when they contract, the cheek is pulled inward.
Temporomandibular joint (TMJ) syndrome
The temporomandibular joint or TMJ acts like a sliding hinge, connecting your jawbone to your skull. Dysfunction can lead to pain and discomfort.
Jaw pain, difficulty chewing, and clicking and locking of the jaw joint are some of the symptoms.
Common treatments include medications, bite guards, and physical therapy.
zygomaticus major
is a muscle of the human body. It is a muscle of facial expression which draws the angle of the mouth superiorly and posteriorly to allow one to smile.
zygomaticus minor
is a muscle of facial expression. It originates from zygomatic bone and continues with orbicularis oculi on the lateral face of the levator labii superioris and then inserts into the outer part of the upper lip. It draws the upper lip backward, upward, and outward and is used in smiling.
Muscles of Mastication
- The masseter (composed of the superficial and deep head)
- The temporalis (the sphenomandibularis is considered a part of the temporalis by some sources, and a distinct muscle by others)
- The medial pterygoid.
- The lateral pterygoid.
masseter
is a thick, flattened muscle that can be felt just in front of the ear when the teeth are clenched. Its fibers run downward from the zygomatic arch to the mandible. The masseter raises the jaw, but it can also control the rate at which the jaw falls open in response to gravity
temporalis
is a fan-shaped muscle located on the side of the skull above and in front of the ear. Its fibers, which also raise the jaw, pass downward beneath the zygomatic arch to the mandible. Tensing this muscle is associated with temporomandibular joint syndrome
medial pterygoid
runs back and downward from the sphenoid, palatine, and maxillary bones to the ramus of the mandible. It closes the jaw and moves it from side to side.
lateral pterygoid
run from the region just below the mandibular condyle forward to the sphenoid bone. This muscle can open the mouth, pull the mandible forward to make it protrude, and move the mandible from side to side
Muscles That Move the Head and Vertebral Column
Sternocleidomastoid Quadratus lumborum Splenius capitis Erector spinae Semispinalis capitis Scalenes
sternocleidomastoid
is a long muscle in the side of the neck that runs upward from the thorax to the base of the skull behind the ear. When the sternocleidomastoid on one side contracts, the face turns to the opposite side. When both muscles contract, the head is pulled toward the chest. If other muscles fix the head in position, the sternocleidomastoids can raise the sternum, aiding forceful inhalation
splenius capitis
is a broad, straplike muscle in the back of the neck. It connects the base of the skull to the vertebrae in the neck and upper thorax. A splenius capitis acting singly rotates the head and laterally flexes the neck. Acting together, these muscles bring the head into an upright position
semispinalis capitis
is a broad, sheetlike muscle running upward from the vertebrae in the neck and thorax to the occipital bone and mastoid processes of the temporal bones. It extends and laterally flexes the neck or rotates the head
scalene
muscles (anterior, middle, and posterior) are synergistic with the sternocleidomastoid for flexion of the neck. They also assist with forceful breathing by elevating the first two ribs
quadratus lumborum
is located in the lumbar region. When the quadratus lumborum muscles on both sides contract, the vertebral column is extended. When the muscle on only one side contracts, the vertebral column is flexed laterally.
Erector spinae
muscles run longitudinally along the back, with origins and insertions at many places on the axial skeleton. These muscles extend the neck and rotate the head and maintain the erect position of the vertebral column. In the neck region they are aided by an elastic ligament (ligamentum nuchae), which limits flexion of the neck and helps to hold the head upright. Erector spinae can be subdivided into lateral, intermediate, and medial groups
Muscles That Move the Pectoral Girdle
Trapezius Levator scapulae Rhomboid major Serratus anterior Rhomboid minor Pectoralis minor
trapezius
is a large, triangular muscle in the upper back that runs horizontally from the base of the skull and the cervical and thoracic vertebrae to the shoulder. Its fibers are organized into three groups—upper, middle, and lower. Together these fibers rotate the scapula. The upper fibers acting alone raise the scapula and shoulder, such as when shrugging the shoulders to express a feeling of indifference. The middle fibers pull the scapula toward the vertebral column, and the lower fibers draw the scapula and shoulder downward. When other muscles fix the shoulder in position, the trapezius can pull the head backward or to one side
Rhomboid major
is a skeletal muscle on the back that connects the scapula with the vertebrae of the spinal column. In human anatomy, it acts together with the rhomboid minor to keep the scapula pressed against thoracic wall and to retract the scapula toward the vertebral column.
Rhomboid minor
is a small skeletal muscle on the back that connects the scapula with the vertebrae of the spinal column. Located inferior to levator scapulae and superior to rhomboid major, it acts together with the latter to keep the scapula pressed against the thoracic wall.
levator scapulae
is a straplike muscle that runs almost vertically through the neck, connecting the cervical vertebrae to the scapula. It elevates the scapula
serratus anterior
is a broad, curved muscle located on the side of the chest. It arises as fleshy, narrow strips on the upper ribs and continues along the medial wall of the axilla to the ventral surface of the scapula. It pulls the scapula downward and anteriorly and is used to thrust the shoulder forward, as when pushing something
pectoralis minor
is a thin, flat muscle that lies beneath the larger pectoralis major. It runs laterally and upward from the ribs to the scapula and pulls the scapula forward and downward. When other muscles fix the scapula in position, the pectoralis minor can raise the ribs and thus aid forceful inhalation
Muscles That Move the Arm
*Flexors
Coracobrachialis
Pectoralis major
*Abductors
Supraspinatus
Deltoid
*Extensors
Teres major
Latissimus dorsi
*Rotators
Subscapularis
Infraspinatus
Teres minor
coracobrachialis
runs from the scapula to the middle of the humerus along its medial surface. It flexes and adducts the arm
pectoralis major
is a thick, fan-shaped muscle in the upper chest. Its fibers run from the center of the thorax through the armpit to the humerus. This muscle primarily pulls the arm forward and across the chest. It can also rotate the humerus medially and adduct the arm from a raised position
teres major
connects the scapula to the humerus. It extends the shoulder and can also adduct and rotate the arm medially
latissimus dorsi
is a wide, triangular muscle that curves upward from the lower back, around the side, and to the armpit. It can extend the shoulder and adduct the arm and rotate the humerus medially. It also pulls the shoulder downward and back. The actions of pulling the arm back in swimming, climbing, and rowing use this muscle
triangle of auscultation
is located in the back where the trapezius overlaps the superior border of the latissimus dorsi and the underlying rhomboid major. This area, near the medial border of the scapula, enlarges when a person bends forward with the arms folded across the chest. By placing the bell of a stethoscope in the triangle of auscultation, a physician can usually clearly hear the sounds of the respiratory organs.
supraspinatus
is located in the depression above the spine of the scapula on its posterior surface. It connects the scapula to the greater tubercle of the humerus and abducts the arm
deltoid
is a thick, triangular muscle that covers the shoulder joint. It connects the clavicle and scapula to the lateral side of the humerus and abducts the arm. The deltoid’s posterior fibers can extend the shoulder, and its anterior fibers can flex the shoulder
subscapularis
is a large, triangular muscle that covers the anterior surface of the scapula. It connects the scapula to the humerus and rotates the arm medially
infraspinatus
occupies the depression below the spine of the scapula on its posterior surface. The fibers of this muscle attach the scapula to the humerus and rotate the arm laterally
teres minor
is a small muscle connecting the scapula to the humerus. It rotates the arm laterally
Muscles That Move the Forearm
*Flexors
Biceps brachii
Brachialis
Brachioradialis
*Extensor
Triceps brachii
*Rotators
Supinator
Pronator teres
Pronator quadratus
biceps brachii
is a fleshy muscle that forms a long, rounded mass on the anterior side of the arm. It connects the scapula to the radius and flexes the elbow and rotates the hand laterally (supination), as when a person turns a doorknob or screwdriver
brachialis
is a large muscle beneath the biceps brachii. It connects the shaft of the humerus to the ulna and is the strongest flexor of the elbow
brachioradialis
connects the humerus to the radius. It aids in flexing the elbow
triceps brachii
has three heads and is the only muscle on the back of the arm. It connects the humerus and scapula to the ulna and is the primary extensor of the elbow
supinator
is a short muscle whose fibers run from the ulna and the lateral end of the humerus to the radius. It assists the biceps brachii in rotating the forearm laterally, such as when turning the hand so the palm faces upward (supination)
pronator teres
is a short muscle connecting the ends of the humerus and ulna to the radius. It rotates the arm medially, such as when turning the hand so the palm faces downward (pronation)
pronator quadratus
runs from the distal end of the ulna to the distal end of the radius. It assists the pronator teres in rotating the arm medially
Muscles That Move the Hand
*FlexorsFlexor carpi radialis Flexor carpi ulnaris Palmaris longus Extensor carpi ulnaris Flexor digitorum profundus Flexor digitorum superficialis
*Extensors Extensor carpi radialis longus Extensor digitorum Extensor carpi radialis brevis Flexor carpi ulnaris
flexor carpi radialis
is a fleshy muscle located medially on the anterior side of the forearm. It runs from the distal end of the humerus into the hand, where it is attached to metacarpal bones. The flexor carpi radialis flexes the wrist and abducts the hand
flexor carpi ulnaris
is located along the medial border of the forearm. It connects the distal end of the humerus and the proximal end of the ulna to carpal and metacarpal bones. It flexes the wrist and adducts the hand
palmaris longus
is a slender muscle located on the medial side of the forearm between the flexor carpi radialis and the flexor carpi ulnaris. It connects the distal end of the humerus to fascia of the palm and flexes the wrist
flexor digitorum profundus
is a slender muscle located on the medial side of the forearm between the flexor carpi radialis and the flexor carpi ulnaris. It connects the distal end of the humerus to fascia of the palm and flexes the wrist
flexor digitorum profundus
is a large muscle that connects the ulna to the distal phalanges. It flexes the distal joints of the fingers, such as when making a fist
flexor digitorum superficialis
is a large muscle located beneath the flexor carpi ulnaris. It arises by three heads—one from the medial epicondyle of the humerus, one from the medial side of the ulna, and one from the radius. It is inserted in the tendons of the fingers and flexes the fingers and, by a combined action, flexes the wrist
extensor carpi radialis longus
runs along the lateral side of the forearm, connecting the humerus to the hand. It extends the wrist and assists in abducting the hand
extensor carpi radialis brevis
is a companion of the extensor carpi radialis longus and is located medially to it. This muscle runs from the humerus to the metacarpal bones and extends the wrist. It also assists in abducting the hand
extensor carpi ulnaris
is located along the posterior surface of the ulna and connects the humerus to the hand. It extends the wrist and assists in adducting the hand
extensor digitorum
runs medially along the back of the forearm. It connects the humerus to the posterior surface of the phalanges and extends the fingers
extensor retinaculum
(dorsal carpal ligament, or posterior annular ligament) is an anatomical term for the thickened part of the antebrachial fascia that holds the tendons of the extensor muscles in place. It is located on the back of the forearm, just proximal to the hand. **Carpal Tunnel **
Muscles of the Abdominal Wall
External oblique
Transversus abdominis
Internal oblique
Rectus abdominis
linea alba
is a single midline fibrous line in the anterior abdominal wall formed by the median fusion of the layers of the rectus sheath medial to the bilateral rectus abdominis muscles. It attaches to the xiphoid process of the sternum and the pubic symphysis.
external oblique
, is a broad, thin sheet of muscle whose fibers slant downward from the lower ribs to the pelvic girdle and the linea alba. When this muscle contracts, it tenses the abdominal wall and compresses the contents of the abdominal cavity.
internal oblique
which is a broad, thin sheet of muscle beneath the external oblique. Its fibers run up and forward from the pelvic girdle to the lower ribs.
transversus abdominis
forms a third layer of muscle beneath the external and internal obliques. Its fibers run horizontally from the lower ribs, lumbar vertebrae, and ilium to the linea alba and pubic bones. It functions in the same manner as the external and internal obliques.
rectus abdominis
is a long, strap-like muscle that connects the pubic bones to the ribs and sternum. Three or more fibrous bands cross the muscle transversely, giving it a segmented appearance. The muscle functions with other abdominal wall muscles to compress the contents of the abdominal cavity, and it also helps to flex the vertebral column.
Muscles of the Pelvic Floor and Perineum
*Pelvic Floor
Levator ani
Coccygeus
*Other perineal muscles Bulbospongiosus Ischiocavernosus External anal sphincter Superficial transversus perinei
*Urogenital Diaphragm
Deep transversus perinei
External urethral sphincter
pelvic floor
A muscular sheet, the pelvic floor (pelvic diaphragm) supports the pelvic viscera.
perineum
Inferior to the pelvic floor is the perineum, the lowermost part of the trunk, which contains the anal canal, anus, urethra, and external genital organs.
urogenital diaphragm
fills the space within the pubic arch.
levator ani
muscles originate from the pubis and ischium on both sides and join at midline to form a thin sheet across the pelvic outlet. Their joining is interrupted in the male by the urethra and the anal canal, and in the female by the urethra, vagina, and anal canal. These muscles help support the pelvic viscera and provide sphincterlike action in the anal canal and vagina.
coccygeus
is a fan-shaped muscle that extends between the ischial spine and the coccyx and sacrum. It aids the levator ani.
deep transversus perinei
is formed from two muscles that extend from each ischium to the central tendon.
external urethral sphincter
is formed from two muscles that arise from the pubic and ischial bones. Each arches around the urethra and unites with the one on the other side. Together they close the urethra by compression and open it by relaxation, helping control the flow of urine.
superficial transversus perinei
consists of a small bundle of muscle fibers that passes medially from the ischial tuberosity along the posterior border of the urogenital diaphragm. It supports the central tendon.
bulbospongiosus
muscles join medially to surround the base of the penis and assist in emptying the urethra. In the female, these muscles join to surround the vagina, and constrict the vaginal opening. These muscles can also slow blood flow in veins, which helps maintain erection of the penis in the male and of the clitoris in the female.
ischiocavernosus
muscle runs from the ischial tuberosity to the margin of the pubic arch. It assists erection of the penis in males and the clitoris in females.
external anal sphincter
is under voluntary control. It encircles the anal canal and keeps it closed when contracted.
Muscles That Move the Thigh
*Anterior Group
Psoas major
Iliacus
*Posterior Group Gluteus maximus Gluteus medius Gluteus minimus Piriformis Tensor fasciae latae
*Medial Group Pectineus Adductor magnus Adductor brevis Gracilis Adductor longus
psoas major
is a long, thick muscle that connects the lumbar vertebrae to the femur. It flexes the hip
iliacus
a large, fan-shaped muscle, lies along the lateral side of the psoas major. The iliacus and the psoas major are the primary flexors of the hip, and they advance the lower limb in walking movements
gluteus maximus
is the largest muscle in the body and covers a large part of each buttock. It connects the ilium, sacrum, and coccyx to the femur by fascia of the thigh and extends the hip. The gluteus maximus helps to straighten the lower limb at the hip when a person walks, runs, or climbs. It is also used to raise the body from a sitting position
gluteus medius
is partly covered by the gluteus maximus. Its fibers run from the ilium to the femur, and they abduct the thigh and rotate it medially
gluteus minimus
lies beneath the gluteus medius and is its companion in attachments and functions
piriformis
is shaped like a pyramid and located inferior to the gluteus minimus. It abducts and laterally rotates the thigh and is part of the posterior group of muscles that stabilizes the hip.
tensor fasciae latae
connects the ilium to the iliotibial tract (fascia of the thigh), which continues downward to the tibia. This muscle flexes the hip and abducts and rotates the thigh medially
pectineus
muscle runs from the spine of the pubis to the femur. It flexes the hip and adducts the thigh
adductor brevis
is a short, triangular muscle that runs from the pubic bone to the femur. It adducts the thigh and assists in flexing the hip
adductor longus
is a long, triangular muscle that runs from the pubic bone to the femur. It adducts the thigh and assists in flexing the hip and rotating the thigh laterally
adductor magnus
is the largest adductor of the thigh. It is a triangular muscle that connects the ischium to the femur. It adducts the thigh and portions assist in flexing or extending the hip
gracilis
is a long, straplike muscle that passes from the pubic bone to the tibia. It adducts the thigh and flexes the knee
Muscles That Move the Leg
*Flexors - Hamstring group Biceps femoris Semitendinosus Semimembranosus Sartorius
*Extensors - Quadriceps femoris group Rectus femoris Vastus lateralis Vastus medialis Vastus intermedius
hamstring - posterior thigh
The large muscle group on the posterior thigh called the hamstring is the primary flexor of the knee. Its three parts are the biceps femoris, the semitendinosus, and the semimembranosus.
biceps femoris
has two heads, one attached to the ischium and the other attached to the femur. This muscle passes along the back of the thigh on the lateral side and connects to the proximal ends of the fibula and tibia. The biceps femoris is one of the hamstring muscles, and its tendon (hamstring) feels like a lateral ridge behind the knee. This muscle flexes the knee, rotates the leg laterally, and extends the hip
semitendinosus
is another hamstring muscle. It is a long, bandlike muscle on the back of the thigh toward the medial side, connecting the ischium to the proximal end of the tibia. The semitendinosus is so named because it becomes tendinous in the middle of the thigh, continuing to its insertion as a long, cordlike tendon. It flexes the knee, rotates the leg medially, and extends the hip
semimembranosus
is the third hamstring muscle and is the most medially located muscle in the back of the thigh. It connects the ischium to the tibia and flexes the knee, rotates the leg medially, and extends the hip
sartorius
is an elongated, straplike muscle that passes obliquely across the front of the thigh and then descends over the medial side of the knee. It connects the ilium to the tibia and flexes the knee and the hip. It can also abduct the thigh, rotate the thigh laterally, and rotate the leg medially
quadriceps femoris (Quads) - Anterior
The large muscle group called the quadriceps femoris occupies the front and sides of the thigh and is the primary extensor of the knee.
rectus femoris
is part of the quadriceps group. It is a bulk of muscle located in the superior, anterior middle compartment of the thigh and is the only muscle in the quadriceps group that crosses the hip.
vastus lateralis
muscle is located on the lateral side of the thigh. This muscle is the largest of the quadriceps which includes: rectus femoris, vastus intermedius, and vastus medialis.
vastus medialis (vastus internus or teardrop muscle)
is an extensor muscle located medially in the thigh that extends the knee. The vastus medialis is part of the quadriceps muscle group.
vastus intermedius
arises from the front and lateral surfaces of the body of the femur in its upper two-thirds, sitting under the rectus femoris muscle and from the lower part of the lateral intermuscular septum.
Muscles That Move the Foot
*Dorsiflexors Tibialis anterior Fibularis tertius Extensor digitorum longus Extensor hallucis longus
*Invertor
Tibialis posterior
*Plantar Flexors Gastrocnemius Soleus Plantaris Flexor digitorum longus
*Evertor
Fibularis longus
tibialis anterior
is an elongated, spindle-shaped muscle located on the front of the leg. It arises from the surface of the tibia, passes medially over the distal end of the tibia, and attaches to bones of the foot. Contraction of the tibialis anterior causes dorsiflexion and inversion of the foot
fibularis (peroneus) tertius
is a muscle of variable size that connects the fibula to the lateral side of the foot. It functions in dorsiflexion and eversion of the foot
extensor digitorum longus
is situated along the lateral side of the leg just behind the tibialis anterior. It arises from the proximal end of the tibia and the shaft of the fibula. Its tendon divides into four parts as it passes over the front of the ankle. These parts continue over the surface of the foot and attach to the four lateral toes. The actions of the extensor digitorum longus include dorsiflexion of the foot, eversion of the foot, and extension of the toes
gastrocnemius
on the back of the leg forms part of the calf. It arises by two heads from the femur. The distal end of this muscle joins the strong calcaneal tendon (Achilles tendon), which descends to the heel and attaches to the calcaneus. The gastrocnemius is a powerful plantar flexor of the foot that aids in pushing the body forward when a person walks or runs. It also flexes the knee
soleus
is a thick, flat muscle located beneath the gastrocnemius, and together these two muscles form the calf of the leg. The soleus arises from the tibia and fibula, and it inserts at the heel by way of the calcaneal tendon. It acts with the gastrocnemius to cause plantar flexion of the foot
plantaris
connects the femur to the heel, where it inserts with the gastrocnemius and soleus via the calcaneal tendon. When the plantaris contracts it plantar flexes the foot, and because it crosses the knee joint, it also flexes the knee.
flexor digitorum longus
runs from the posterior surface of the tibia to the foot. Its tendon passes along the plantar surface of the foot. There the tendon divides into four parts that attach to the distal phalanges of the four lateral toes. This muscle assists in plantar flexion of the foot, flexion of the four lateral toes, and inversion of the foot
tibialis posterior
is the deepest of the muscles on the back of the leg. It connects the fibula and tibia to the ankle bones by means of a tendon that curves under the medial malleolus. This muscle assists in inversion and plantar flexion of the foot.
- Extensor hallucis longus also inverts the foot, because it pulls up on the medial portion
fibularis (peroneus) longus
is a long, straplike muscle located on the lateral side of the leg. It connects the tibia and the fibula to the foot by means of a stout tendon that passes behind the lateral malleolus. It everts the foot, assists in plantar flexion, and helps support the arch of the foot
