Chapter 24- Thoracic Wall

what is the function of the thoracic wall?

to form a protective cavity for the:

1. heart

2. lungs

3. for the organs of the superior aspect of the abdomen

what are the bones of the thoracic wall?

1. sternum

2. ribs

sternum is also known as

breast bone

what is the sternum?

a flat bone (4, 5, 6)

where is the sternum located?

anterior aspect of the thorax in the midline

from Greek, sternon means what?

breast of man

how many parts is the sternum divided into? what are they?

3 parts:

1. manubrium (4)

2. body (5)

3. xiphoid process (6)

what is the manubrium?

the superior portion of the sternum (4)

from Latin, manus means what?

hand

what is the sternum fancied to resemble?

a sword, with the manubrium being the part of the sword held in the hand

what is the jugular notch?

found on the superior border of the manubrium

what does the manubrium articulate with?

the clavicle and first 2 pairs of costal cartilage (hyaline cartilage between ribs and sternum)

what is the body?

middle portion of the sternum (5); long, narrow, and thinner than the manubrium

what does the body articulate with?

the costal cartilages of ribs 2-7

what is the sternal angle?

the junction of the manubrium and body

why is the sternal angle important?

it is a palpable landmark for counting ribs

what is the xiphoid process?

SMALLEST, most variable, and inferior portion of the sternum (6)

from Greek, xiphon and oeides means what?

sword shaped

what is the epigastric fossa?

(pit of the stomach) depression on the ANTERIOR aspect of the xiphoid process; it is palpable and often visible

what is the xiphisternal joint?

found between the xiphoid process and the body at the superior aspect of the epigastric fossa

from Latin, costa means what?

rib

what are ribs (aka ____)?

-costae

-12 elongated pairs of flat bones that FORM MOST OF THE THORACIC WALL (1, 2)

how many ribs do humans have?

12 ribs on each side of the body (variation include cervical ribs at CV7 or lumbar ribs at LV1)

the elongated flattened bones course where?

anteriorly and inferiorly from the thoracic vertebrae

what does the head portion of the rib articulate with?

the bodies of the thoracic vertebrae

what is the neck portion of the rib?

constricted portion lateral to the head

where is the tubercle of the rib located?

posterior projection lateral to the neck

what does the tubercle articulate with?

the transverse process of its respective thoracic vertebrae

what is the body of the rib?

the shaft of the rib

what is the angle of the rib?

the point where the curve (or angle) of the rib is the sharpest

what does the anterior end of the rib articulate with?

costal cartilage

what is the costal groove?

the ridge that lies on the inferior surface of the shaft of the rib

what lies in the costal groove?

from superior to inferior:

the intercostal vein, artery, and nerve

where does the length of the rib increase? where does it decrease?

1st to 7th rib; to the 12th rib

what are the first seven ribs called?

true ribs (1)

where are the true ribs directly connected?

to the sternum via their costal cartilages (3)

what are the last five ribs called?

false ribs (2)

each costal cartilage of ribs 8, 9, and 10 joins what?

its respective suprajacent costal cartilage (8 to 7, 9 to 8, 10 to 9)

where do the costal cartilages of ribs 11 and 12 end? what are these ribs (11 and 12) also classified as?

blindly in muscle with no anterior articulation; floating ribs

what is the costal margin formed by?

costal cartilages of ribs 7, 8, 9, and 10, which course medially and superiorly

-where do the costal margins intersect?

-what is the intersection of the costal margins termed?

-at the xiphisternal joint

-infrasternal angle

what is the superior thoracic aperture bounded by?

upper border of the sternum and by the first ribs

what is the superior thoracic aperture?

an opening through which the great vessels and visceral tubes ascend or descend between the thorax and the neck

what is the inferior thoracic aperture normally closed by?

the diaphragm

how many openings are found in the diaphragm?

3 major openings

what do these 3 major openings allow for?

the passage of the inferior vena cava, esophagus, and aorta

what are the three layers the muscles of the thorax are arranged in?

1. external layer

2. middle layer

3. internal layer

which muscles are part of the external layer?

external intercostal muscles

which muscles are part of the middle layer?

internal intercostal muscles

which muscles are part of the internal layer?

innermost intercostal musles

what is the origin of the external intercostal muscles?

lower margin of the rib above

what is the insertion of the external intercostal muscles?

upper margin of the rib below

what is the action of the external intercostal muscles?

elevation of the ribs during inspiration

what is the innervation of the external intercostal muscles?

-intercostal nerves T1 to T6

-thoracoabdominal nerves T7 to T11

how many pairs of external intercostal muscles are there?

11

from Latin inter= and costa=

between; rib

from their point of origin, the fibers of the external intercostal muscles pass where?

medially and inferiorly to their point of insertion

what happens to the external intercostal muscles in the intercostal spaces?

the muscles extend from the tubercle of the rib posteriorly to the region of the costochondral junction anteriorly

what happens at or near the costochondral junction?

the muscles thin out and become membranous where they are then referred to as the external intercostal membrane

what is the origin of the internal intercostal muscles?

upper margin of the rib below and its costal cartilage

what is the insertion of the internal intercostal muscles?

lower margin of the rib above and its costal cartilage

what is the action of the internal intercostal muscles?

depression of the ribs during expiration

what is the innervation of the internal intercostal muscles?

-intercostal nerves T1 to T6

-thoracoabdominal nerves T7 to T11

how many pairs of internal intercostal muscles are there?

11

from internal intercostal muscles point of origin, the fibers of these muscles pass where?

medially and superiorly to their point of insertion

in the intercostal spaces, the muscles extend where?

from the sternum anteriorly to the angles of the ribs posteriorly where they thin out and form the internal intercostal membrane

how many pairs of innermost intercostal muscles are there?

11

innermost intercostal muscles have the same?

origin, insertion, action and innervation as the internal intercostal muscles

review:

origin = upper margin of the rib below and its costal cartilage

insertion = lower margin of the rib above and its costal cartilage

action = depression of the ribs during expiration

innervation = intercostal nerves T1-T6; thoracoabdominal nerves T7-T11

innermost intercostal muscles are separated from what? by what?

-the internal intercostals

-by the intercostal vessels and nerve

what is the area between the internal and innermost intercostal muscles named?

neurovascular plane

what other muscles are also associated with the thoracic wall?

transversus thoracis and subcostales

how many thoracic spinal nerves are there?

12

where do all the thoracic spinal nerves traverse?

where do they divide?

-an intervertebral foramen

-divide into a dorsal ramus and ventral ramus

where do the dorsal rami course?

posteriorly and divide into medial and lateral branches

what are the ventral rami?

larger branches of the spinal nerves that course forward into the intercostal spaces

what are the regional names of the ventral rami?

1. T1-T6: Intercostal nerves (proper)

2. T7-T11: Thoracoabdominal nerves

3. T12: Subcostal nerves

how does a typical intercostal nerve course?

1. it passes below the neck of the rib numerically corresponding to it; EX: T4 courses inferior to the fourth thoracic rib

what is the second step? (where does it now course?)

it courses between the innermost intercostal and the internal intercostal muscles in the neurovascular plane

what is the third step? (where does it pass forward in? where does it course?)

it passes forward in the costal groove on the lower surface of the rib, where it courses inferior to the intercostal vein and artery

what is the fourth step? (what does it give off?)

it gives off a lateral cutaneous branch

what does the lateral cutaneous branch pierce?

the internal intercostal, external intercostal, and serratus anterior muscles

what does the nerve then divide into/supply?

anterior and posterior branches that supply the skin of the chest wall

what is the last step? (what happens at the anterior end of the intercostal space?)

at the anterior end of the intercostal space, it turns forward through the internal intercostal muscle, the external intercostal membrane, and the pectoralis major muscle

what is the intercostal nerve now distributed as?

the anterior cutaneous branch to the skin of the front of the chest

what are breasts?

SWEAT GLANDS modified to produce MILK

what is the major function of the breast (sweat gland)?

lactation --> secrete milk for the nourishment of the child

Latin for breast = ______, thus the name ________

mammae; mammary gland

what is the main constituent of the mammary gland?

the 15-20 lobes of the glandular tissue (alveoli)

what do the lobes contain?

alveoli or milk-secreting mammary epithelial cells

how are the lobes arranged?

grape-like clusters

of these lobes, how many assume the entire functional load?

6-8

what happens to the remaining majority?

small and poorly developed

what is surrounding and overlying the glandular tissue?

a large amount of FAT, which makes up the majority of the organ

what is each lobe drained by?

a lactiferous duct that dilates near its termination

what is the dilation called?

lactiferous sinus

where does the duct empty?

at the nipple

where does the axillary tail extend?

into the axilla

where is breast tissue firmly attached to?

skin over much of the remainder of the organ

what is the breast tissue attached to skin by? where is this especially represented in?

heavy ligamentous bands of connective tissue; in the well-developed "retinacula cutis"

what do the well-developed "retinacula cutis" do?

traverse and subdivide the fat and anchor the glandular tissue to the skin