Anatomy - Outcome 11 Flashcards
What are muscles composed of?
Each muscle is composed of several small fibers held together by a thin membrane like fascia which allows the muscles to be serparated from other structures in the area
Each muscle has an origin and an insertion…
the orgin is usually fixed, or the least movable structure
the insertion is usually attached to the more moveable structure
What percentage do muscles make up of the body’s weight?
40-50%
There are essentially 3 types of muscle tissue:
- cardiac - found in the heart
- smooth - located in the stomach, intestinal walls, blood vessels, urinary tract and ducts
- skeletal - responsible for bodily movements and breathing
Skeletal Muscle
Each skeletal muscle consists of a body and two attachments. The body contains muscular tissue. The attachments are fibrous tissue and attach the muscle at both ends to bones, ligaments, tendons, skin, or sometimes to each other
Depression definition
to lower or closer
Elevation definition
to lift or close
Lateral excursion definition
to move side to side
Mastication definition
to chew and grind
Protrusion definition
to move forward or extend
Retrusion definition
to pull backward or inwards
What is Mastication?
a series of highly coordinated functions that involve the teeth, tongue, muscles of mastication, lips, cheeks, and sailva in the preparation of food for swallowing and digestion
There are three starges of mastication:
- Cutting of food
- Crushing of food into smaller particles
- Grinding of food
When the impulse to massticate food..
When the impulse to masticate food is relayed along with the muscles of mastication, the mucle fibers shorten, pulling toward their origin and thus providing joint action. This reflex action allows the muscles of mastication to play a major role in preparing food for swalloing
The rest position
The teeth are arranged in both arches so that when the muscles of mastication bring the jaws together, the teeth meet in a function relationship known as occlusion, with the upper and lower teeth not quite in contact, but with a space of 2 to 5mm betwween the anterior teeth. This is known as the rest position
The muscles of mastication have the ability to…
Have the ability to move the lower jaw (mandible) from side to side, as well as the ability to protract or retract the mandible
The act of mastication consists of…
Placing food between the anterior teeth and closing until the teeth meet with the lower incisors to the lingual of the upper incisors. Then, with a shearing motion, a piece of food is cut free. The portion is then transfered by the tongue to the posterior teeth and is held in position by the cheeks and positerior teeth to reduce the food to “bits”. After the food has been prepared for swallowing, the tongue propels it against the posterior of the palate and into the pharynx, and down into the stomache
Masseter Muscle - Origin & Insertion
Origin: zygomatic arach (lower boder and medial side) fibers run downard and slightly backward
Insertion: angle of the mandible, lateral side
Temporal Muscle - Origin & Insertion
Origin: Temporal fossa superior to the suture joining the temporal and paretal bones
Insertion: Coronoid process of the mandible
The Medial (Internal) Pterygoid - Origin & Insertion
Origin: pterygoid plate and fossa (part of the sphenoid bone) and maxillary tuberosity
Insertion: angle of the mandible (medial side)
The Lateral (External) Pterygoid - Origin & Insertion
Origin: has 2 separate origins..
-greater wing of the sphenoid bone
-pterygoid plate of the sphenoid bone
Insertion: temporomandibular joint neck of the condyle
The Masseter Muscle Function
-probably the most powerful of the muscles of mastication
Function:
1. Elevates the mandible, closing the mouth
2. Clenches the teeth
3. Brings the molars together for crushing and grinding
The Temporal Muscle (Temporalis) Function
- has a wide span and supports the overall action of closing the lower jaw ultimately closing the mouth
Function:
1. Elevation of the mandible, forceful retraction, and retrution of the mandible
2. The final “squeeze” when closing
The Medial (Internal) Pterygoid Function
- This muscle parallels the masseter but iis not as powerful. The masseter and the medial pterygoid form a “sling” for the mandible, with the masseters inserting on the lateral side and the medial pterygoid inserting on the medial side of the angle of the mandible
Function:
1. Elevate the mandible, close the mouth
The Lateral (External) Pterygoid Function
-is a short, thick muscle that extends horizontally, in a posterior direction
Function:
1. Protrusion of the mandible
2. Side-to-side movement of the mandible
What muscles accomplish depression of the mandible/opening the mouth?
Muscles in the neck referred to as the hyoid muscles accomplish opening the mouth
The Hyoid Bone
A horshoe-shaped bone suspended beneath the mandible
2 Groups of the Hyoid Muscles
The suprahyoid (above the hyoid) muscles
The infrahyoid (below the hyoid) muscles
The suprahyoid muscle group includes
-digastric muscle
-stylohyoid muscle
-mylohyoid muscle
-geniohyoid muscle
The muscles form the floor of the mouth. They are responsible for the elevation of the hyoid bone, as well as the depression of the mandible
The infrahyoid muscle groups include
-omohyoid muscle
-sternohyoid muscle
-stenothyroid muscle
-thyrohyoid muscle
- these muscles are responsible for depressing the hyoid bone and the larynx. They are located deep within the throat area
The Muscles of Mastication
-Massetter Muscle
-Temporal Muscle
-The Medial (Internal) Pterygoid
-The Lateral (External) Pterygoid
The Muscles of Facial Expression
-Buccinator Muscle
-The Orbicuaris Oris
-The Mentalis Muscle
-The Zygomatic Major
-The Zygomatic Minor
Buccinator Muscle Origin & Insertion
Origin: alveolar process, molar area, buccal aspect
Insertion: obicularis oris, at the corners of the mouth
The Orbiularis Oris Origin & Insertion
Origin: many layers of fibers surrounding the mouth
Insertion: angles of the mouth
The Mentalis Muscle Origin & Insertion
Origin: Anterior surface of the mandible, just below the lateral incisors
Insertion: skin of the chin
The Zygomatic Major Origin & Insertion
Origin: zygomatic bone
Insertion: into the orbicularis oris at the angle of the mouth
The Zygomatic Minor Origin & Insertion
Origin: Zygomatic bone
Insertion: Orbicularis oris, toward the midline
Paired Muscles of Facial Expression
The actions of paired muscles on each side of the face are usually symmetrical. A loss of symmetry may often be an early sign of injury to the facial nerve on one side
Muscles of Facial Expression - Superficial vs. Deeper
it should be noted that some are superficial, while others are located deeper within the body.
The Buccinator Muscle Function
-is the principle cheek muscle. Although it is a muscle of facial expression, it also plays a role in mastication
Function:
1. Pulls the corners of the mouth backward
2. Compresses the cheeks
3. Forces food onto occlusal surfaces of teeth
4. Expels air between the lips
The Orbicularis Oris Function
-sometimes called the kissing muscle. It circles the oral cavity in the tissue of the lips
Function:
1. Compresses, contracts and protrudes the lips
2. Keeps food in the mouth
3. Assists in facial expression
The Zygomatic Major Function
-is the prominent muscle on the cheek. It elevates the angle of the mouth creating a smile
Function:
1. Draws the angles of the mouth upward and backward (laughing)
The Zygomatic Minor Function
-is a smaller muscle of the mouth coming from the area of the zygomatic bone. It is ysyalyl a very poorly developed muscle
Function:
1. Raises the upper lip
Muscles of the Neck
-Trapezius
-Sternocleoidmastoid
-Platysma
The Trapezius
- is a large, flat, triangular-shaped muscle covering the back of the neck, shoulder, and clavicle
Origin: occipital bone
Insertion: clavicle and shoulder
Function: moves the head backwards and sideways - turns the skull
The Sternocleoidmastoid
-also called the “sternomastoid” muscle
Origin: The sternum and clavicle
Insertion: the mastoid process of the temporal bone
Function: Tilting and rotating the head
The Platysma
- is a thin sheet of muscle located just below the skin of the neck
Origin: clavicle and shoulder
Insertion: lower border of the mandbile, near the angle of the mouth
Function: wrinkles the skin of the neck and chin and draws lower lip down and back
Extrinsic Muscles of the Tongue Functions
The extrinsic or external muscles of the tongue allow movement and essentially all functions of the tongue. They facilitate speech, swallowing, and position of the tongue
Extrinsic Muscles of the Tongue
-genioglossus
-hypoglossus
-styloglossus
Major Muscles of the Soft Palate Functions
The muscles of the soft palate facilitate swallowing by raising the soft palate. The form the tonsillar pillars and include:
-Palatoglossus
-Palatopharyngeal
