BIOL 2401 A & P I

BIOL 2401 A & P I Lecture Notes Skeletal System : Gross Dr. Weis

SKELETAL SYSTEM

Bones, cartilage, joints, ligaments

Human Skeleton contains 206 bones

Division : Axial skeleton.........longitudinal axis

Appendicular skeleton..girdles, upper and lower limbs

Axial Skeleton : 80 bones

Skull, vertebral column, Ribs & Sternum (Boney thorax), hyoid bone

I. Skull : 22 bones

Subdivisions :

Cranial...........surrounds the brain for protection and anchoring

protect organs for equilibrium/hearing, vision

Facial............surrounds the entrance of digestive & respiratory systems

also helps protect the globe

A. Cranium : 8 bones

consists of the occipital, parietal, temporal, frontal, sphenoid, ethmoid

fxn :: muscle attachment and to enclose and protect the brain

Divided into the

Several bones have sinuses (mucosa lined cavities) called the paranasal sinuses
serve to lighten the skull and secrete mucus for the upper resp. system

Most bones have openings (foramen, fissures) that allow the passage of vessels and nerves

SPECIFIC CRANIAL BONES ::

Occipital (single, non paired), articulates with the parietal bone @ the lamboidal suture and with the temporal bone at the occipitomastoid suture. Will form most of the posterior wall and base of the skull. Major landmark is the Foramen Magnum, a large opening through which the spinal cord leaves the braincase. The occipital condyle is on either side of the Foramen Magnum. This condyle articlulates with the atlas ( the first spinal vertebrae). The hypoglossal canals are located on either side of the occipital condyles to allow passage of Cranial nerve XII (the hypoglossal nerve). Superior to the foramen magnum is the external occipital protuberance for anchoring of the ligamentum nuchae.

Parietal (paired), on either side of the skull, forms the top and superiolateral aspects of the skull and articulates with other cranial bones by sutures ::
coronal, sagittal, lamboidal, and squamous.

Frontal (nonpaired), cranial to parietal bones at the articulation called the coronal suture.
Forms the superior part of the orbit ( eye socket) and the anterior portion of the cranium.
The supraorbital margins of the orbit contain the supraorbital foramen.
The frontal sinuses are located internally, just lateral to the glabella, the smooth surface between the orbits.

Temporal (paired), articulates with the parietal bones @ the squamous suture.

Has four regions :

1. Squamous (flat)

Ethmoid (nonpaired), the perpendicular plate forms the superior part of the nasal septum.
The horizontal plate forms the roof of the nasal cavity, the crista galli (region where brain attaches to the skull by the dura mater)
and the cribiform plate for passage of the olfactory nerves (CN 1).
The left and right lateral mass contains :: the ethmoid sinus, superior and middle conchae and forms the medial wall of the orbit.

B. FACIAL Bones (14 bones)

Nasal, Maxilla, Lacrimal, Zygomatic, Inferior Nasal conchae, Vomer, Palatine, Mandible

Fxn :

Nasal (paired), small bones between the eyes, just inferior to the frontal bone, rectangular shape and forms the bridge of the nose.
(Hyaline cartilage will form most of the external nose).

Maxilla (paired), bones of the upper jaw, also forms the medial part of the orbit, supports the upper teeth and forms the roof of the mouth.
Foramen include infraorbital foramen and the incisive foramen. Houses the maxillary sinuses.
The maxilla is the KEYSTONE of the facial bone, that is, all facial bones will articulate with this bone.

Lacrimal (paired), tear bones in the medial part of orbit, deep to the maxilla. Each bone has a cavity called the lacrimal fossa which houses the lacrimal sac.
With the maxilla, the lacrimal bone will form part of the foramen for the naso- lacrimal duct to permit tear drainage.

Zygomatic (paired), forms the lateral canthus of the orbit. Has the temporal process that joins the zygomatic process of the temporal bone. Commonly called the cheek bone.

Inferior nasal conchae (paired), extends from the maxilla, medially. Largest of the concha and forms part of the lateral walls of the nasal cavity.

Vomer (nonpaired), small bone extending upward from the maxilla and supports the partition that forms part of the nasal septum within the nasal cavity.

Palatine (paired), forms the posterior third of the hard palate and articulates with the maxilla and sphenoid bone.
Also helps form the posteriolateral wall of the nasal cavity by a vertical plate.

Mandible (nonpaired), lower jaw. Regions include the body, angle, and ramus whose processes are the coronoid (under the zygomatic bone) and the condylar process which articulates with the temporal bone @ the mandibular fossa to form a freely moveable joint known as the temporal mandibular joint, also called the TMJ. Anchors the lower teeth (lower arcade). Its foramen include :: mental and mandibular.

C. HYOID BONE

serves as a base for muscles of the tongue and larynx. Has a body and 2 horns : the greater and lesser cornu that are the projections for these muscle attachments. This bone is anchored by ligaments to the styloid process of the temporal bone.

D. OSSICLES

tiny bones of the middle Ear called the malleus, Incus, Stapes

In summary -->

Bones that contribute to the orbit ::

frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal, ethmoid

Bones that contribute to the nasal cavity ::

ethmoid, palatine, maxilla, vomer, nasal, sphenoid, inferior nasal conchae

Paranasal sinuses are housed in 5 skull bones -->

Frontal, Sphenoid, Ethmoid, and both Maxillary bones

The skull of the Infant

the flat bones separated by fibrous Connective Tissue known as fontanelles.

Growth is coordinated with the expansion of the brain.

The body's weight is distributed through the spinal cord by the spinal curves in the thoracic/sacral and lumbar/cervical regions.
Abnormal spinal curves include : scoliosis, kyphosis & lordosis

Vertebrae support the body and protect the spinal cord

Vertebral Anatomy includes : the body, vertebral foramen (canal), spinal process, transverse process for muscle attachment,
articular process with facets between the vertebrae, and the vertebral arch formed by the lamina and the pedicle.

Support for the vertebral column is provided by

1. ligaments :: which can run as long bands down the front and back surface.
Examples --> anterior and posterior longitudinal ligaments or as shorter ligaments that connect each vertebrae to those immediately above or below.
Ex -->ligamenta flava

2. trunk muscles

3. Intervertebral disc (IV disc)
cushion like pad for shock absorption
allow spine to flex and extend

IV discs have an outer fibrocartilage called the annulus fibrosus and an inner soft gelatinous material called the nucleus pulposus

Problems :: rupture of the annulus fibrosus and protrusion of the nucleus pulposus B> called a Herniated Disc

Foramen include ::

vertebral foramen for passage of the spinal cord

intervertebral foramen for passage of spinal nerves

transverse foramen (only present in the cervical vertebrae) for passage of blood vessels

Each vertebrae has characteristic markings and can be written

C1-7 , T 1-12 , L 1-5

A. CERVICAL VERTEBRAE

C1-C7

Seven in number, have short split (bifed) spinous processes and a transverse foramen for blood vessels to the brain. Vertebral foramen are large and have a triangular shape.

The first cervical vertebra is atypical & called the ATLAS. The second cervical vertebra is called the AXIS

The atlas has NO body or spinous process and articulates with the occipital condyles of the skull to form the atlantoccipital joint (the "yes" joint).

The axis has a process known as the DENS and this allows for the pivoting of the atlas and forms a pivot joint (the "no" joint).

There is NO IV disc between C1 and C2.

The seventh cervical vertebra has a long spinous process that is visible through the skin creating a prominent landmark. The transverse foramen is ABSENT in this vertebra.

B. THORACIC VERTEBRAE

T1-T12

Twelve in number, have long slender spinous processes and each articulates with the rib's head and neck at the articular facets of these vertebra.
Their bodies are heart shaped and the vertebral foramen is circular.

Boney Thorax (Thoracic cage) consists of ::

Ribs are bowed flat bones that have a head, neck, tubercle & shaft.

The head articulates with the body of the thoracic vertebra, and the tubercle articulates with the thoracic transverse processes

There are twelve ribs, the first 7 are true (connect to sternum by cartilaginous extensions), the eighth through tenth ribs are called false ribs because they indirectly attach to the sternum, with the last of these (#11 and #12) having no connection to the sternum and are also known as floating ribs.

The sternum has three parts :

C. LUMBAR VERTEBRAE

L1-L5

Five in number, having thick large bodies, long transverse processes, short spinous processes.
The vertebral foramen is triangular. These vertebra "lock" together at their articular processes to provide stability.

These vertebrae support the body's weight, It is a site for back problems, the most common being related to intervertebral disc problems.

D. SACRUM / COCCYX

The sacrum consists of 5 fused vertebrae, (S1-S5).

The ala (which were formerly the transverse processes) articulates with the pelvis and forms the sacroiliac joint & functions for the attachments of the leg muscles.

The sacral promontory is an OB/GYN landmark, and also note the median sacral crest which are the fused spinous processes.

Contains openings :: sacral canal, sacral foramina, and sacral hiatus which is an opening in S4-S5 due to the failure of the vertebral lamina of the arch to fuse.

The coccyx consists of the fusion of 3-5 bones and is the tail remnant. Provides slight support for pelvic organs.

BONES AND FORAMENS :: a summary

Occipital bone Foramen Magnum Spinal cord

Jugular foramen Cranial Nerves 9,10

Temporal Stylomastoid foramen Cranial Nerve , the facial nerve

Internal acoustic meatus Cranial Nerve 8, hearing and balance

Sphenoid Optic foramen CN 2, optic nerve

Supra orbital fissure CN 3, 4, 5 : nerves to move eye muscles

Foramen Ovale CN 5, muscles to jaw

Maxilla Infra orbital foramen Infraorbital nerve

Mandible Mental foramen mental nerve, sensation to lips & chin

Mandibular foramen Mandibular branch of V, sensory to teeth

the area into the Supraspinous Fossa, and the Infraspinous fossa. These regions are for muscle attachments. The subscapular fossa is found on the anterior surface.
The spine is then continuous with the acromion, which articulates with the clavicle at the acaromioclavicular joint and provides attachments for ligaments and tendons.

The scapula will articulate with the humerus at the Glenoid Fossa and this articulation is called the scapulohumeral joint or shoulder joint.
This ball and socket joint is shallow and poorly reinforced so the movement of the humerus is not restricted and the joint flexibility is good, but stability is sacrificed.
Problems :: shoulder dislocations

B. Clavicle

is "S" shaped

originates at the manubrium of the sternum (at the sternal end) and articulates with the acromium of the Scapula,
at its acromial end therefore providing a bridge between the shoulder and rib cage.

Function :

A. Brachium = Humerus (paired) long bone, largest bone of upper extremities

Anatomy includes

1. Head that articulates with the Glenoid fossa of the scapula.

2. Neck......anatomical and surgical areas

inferior to the anatomical neck are the greater and lesser tubercles for muscle attachment.

The tubercles are divided by the inter tubercular groove for the tendon of the biceps brachii m.

The surgical neck is distal to the tubercles

3. Shaft... has a V shaped region for attachment for the Deltoid muscle at the deltoid tuberosity.
The radial groove on the posterior surface is for the radial n.

4. Epicondyles...medial and lateral projections for ligament attachments

5. Condyles ... at the distal epiphysis

divided into the

B. ANTEBRACHIUM (forearm)

Radius, Ulna..... long bones

1. Radius.....paired

located laterally, extends toward the thumb

* Head that articulates with the humeral capitulum & the radial notch of the ulna

* Neck

* Styloid process of the radius at the distal end provides stabilization of the wrist joint,laterally.

Radial Tuberosity on the anterior surface for muscle attachment of the biceps brachii m.

C. Hand

Carpals (short bones), Metacarpals and Phalanges ( long bones)

In each hand.... 1. Carpals 8 bones, classified as short

2 rows, one proximal and one distal

Named from lateral to medial ::

Proximal Row : scaphoid, lunate, triquetral,pisiform

Distal Row : trapezium, trapezoid, capate, hamate

2. Metacarpals #5 and are numbered 1-5 and are long bones,

heads of long bones --> Knuckles

the first metacarpal (#1) articulates with the thumb

3. Phalanges (digits)

fingers have 3 bones (proximal, middle, distal)

thumb (pollex) has 2 bones (proximal and distal)

III. Summary of Articulations of the Arm

A. Scapulohumeral joint (shoulder)

contain bursa which reduce the friction where muscle and tendons cross over joint regions. I
nflammation in this area is called BURSITIS.
Contain ligaments between the clavicle and scapula and between the scapula and humerus.
muscles also help stabilize the joint

B. Olecranon joint (Elbow)

hinge joint due to the action of the olecranon of the ulna with the humerus

the joint capsule and ligaments hold this joint in place

C. Radiocarpal joint

Intercarpal joints

Carpal-Metacarpal joints

are all the joints in the wrist and held in place by collateral ligaments

movements involve : flex, extend, abduction, adduction

D. Metacarpophalangeal joints (at the knuckles)

E. Interphalangeal joints

IV. PELVIC GIRDLE

attaches the lower limb to axial skeleton

transmits upper body weight to the lower limbs

two halves of the os coxa joined at the pubic symphysis

each coxa is the fusion of three bones :

crest----> Iliac crest (wing)

notch --> greater sciatic

surfaces --> gluteal, for the gluteal m.

auricular, articulates with the sacrum

fossa --> Iliac

B. Ischium....anatomy

posterior portion of acetabulum

Components :: body, ramus, spine, tuberosity, notch

ischiatic tuberosity for muscle attachment
ischial spine for ligament attathment
forms part of the obturator foramen (an opening for nerves and vessels)

C. Pubis

anterior portion of the acetabulum

components :; ramus, body, crest, tubercle

part of the obturator foramen

pubis symphysis (joint) between the 2 pubic bones

The pelvis refers to the COXAE, SACRUM, and COCCYX

two areas of importance are the

Patella :: sesmoid bone

tendon insertion for the quadriceps group

components :: base, apex, facets (posterior surface) for femoral condyles

B. Leg : Tibia, Fibula

1) Tibia (shinbone)

medial portion of leg

Condyles, medial and lateral

for articlulation with the femur to transmit weight

divided by the Intercondylar emminence

Tibial Tuberosity on the anterior surface provides for the patellar tendon insertion

Malleolus, medially at the distal end support for the ankle, medially, forms the medial "buldge~ of the ankle

Fibular notch on lateral surface for the distal tibiofibular joint.

2) Fibula

long bone

at the lateral border of the tibia

IS EXCLUDED FROM THE KNEE JOINT, therefore is not involved in weight bearing

Head articulates with the Tibia
Distally, the lateral MALLEOLUS stabilizes the ankle

In summary the fibula is important for : muscle attachment and ankle support
bound to the tibia by an interosseous membrane

C) Foot

Fxn :: supports body weight

lever to propel the body forward due to arches (longitudinal and transverse)

1. Ankle...Tarsus consists of 7 bones, 2 important ones

a. Calcaneous provides for weight bearing
known as the heel bone
calcaneon tendon (achilles tendon) attachment

b. Talus that articulates with the tibia and fibula

The remaining are : Cuboid, Navicular, and the three cuneiforms --> Lateral, Intermediate, and Medial

2. Metatarsals..... long bones

foot bones, involved in weight transfer
Numbered 1-5 :: with metarsal 1 associated with the big toe
heads of the metatarsals form the ball of the foot.

3. Phalanges..... digits

proximal, middle, distal phalanx

first toe known as the Hallux, only has 2 phalangeal bones, the proximal and distal.

Problems :: bunion

clubfoot (varus and valgus forms)

VI. Summary of Articulations for the Lower Extremities

A. Sacroiliac

B. Pubic Symphysis

C. Coxofemoral (Hip)

D. Stifle (Femoraltibial)

E. Tibiofibular

F. Tibiotalar

G. Intertarsal

H. Tarsometatarsal

I. Metatarsophalangeal

J. Interphalangeal

VII. Problems ::

Developmental --> dysplasia of the hip