Lect 6: Thorax and Abdomen

What are the key functions of the thorax?

• PROTECT VITAL ORGANS

• resist neg internal pressure from breathing

• support upper limb weight

• provide muscle attachment points for back / extremities

Thoracic Cage Osteology Overview

True vs False ribs (which #s are which)

1-7 true

8-10 false

11-12 float

What forms the anterior wall of the thoracic cage?

the sternum

Where is the manubrium located? (level)

T3-4

What ia the body of the sternum level with?

T5-9

What ribs articulate with the body of the sternum?

(T2- manubrium and body)

T3-6

(T7 xiphoid process)

How many costal notches are on the body of the sternum?

• 6 pairs

• 2nd-7th costal cartilage

(2 & 7 partial)

Are there any costal notches on the xyphoid process?

yes 1 pair for 7th costal cartilage

Xyphoid process development

initially cartilagenous > ossifies in adulthood

*meaning can vary in shape: point, bifid, or deflected to one side

What type of bone are the ribs?

curved flat bones

What are the true ribs?

ribs 1-7

costal cartilage articulates directly with sternum (costochondral joints)

What are the false ribs?

• ribs 8-10

• attatch to sternum indirectly via cartilage to the rib superior to it

Where do floating ribs attach?

What are the floating ribs?

• ribs 11-12

• don’t attatch to sternum at all

• end in posterior abdominal musculature

What are the (anatomically) typical ribs?

ribs 3-9

• Shaft: outward convexity, costal groove- intercostal arteries/nerves

• Posterior angle: bend in shaft 2” from tubercle

• costal groove: protect intercostal nerve vessels

• tubercle: junction of neck / shaft, has articular + non-articular portions

What does the head of a typical rib articulate with?

(2 facets with transverse crest between)

• upper facet — body of vertebra above

• Lower facet —body of cooresponding vertebra

*sandwhichh sup art proc T5 > up Rib 5 > rib 5 upper facet > T4

Tubercle of the Rib

• junction of neck—shaft

• articular potion: facet for numerically cooresponding TP

• non-articular portion: roughened for ligaments

Which part of the rib articulates with the TP of vertebra?

articular portion of the tubercle

(to cooresponding vert)

What are the anatomically atypical ribs?

1-2

10-12

What is costal cartilage?

• bars of hyaline cartilage

• forward/medial from ant rib ends

• mobility/elasticity to thorax wall

  • (no movement at costochondral joints)

ow many pairs of costal cartilage are there?

12

Where do each pair of costal cartilage connect?

• 1-7 — directly to sternum (costochondral)

• 8-10 — connect to costal cartilage of one above

• 11-12 —just cap floating rib and end in abdomical muscle wall

What type of joints are costovertebral + costotransverse joints?

what do they enable?

plane gliding synovial

*enable elevation + depression

(inhale / exhale)

*strong ligaments so movement is minimal

What parts of the rib do T vertebrae articulate with?

(rib sits on top of numerically cooresponding vert)

body T7 > rib 7 inf facet

TP T7 > tubercle of rib

What joints connect vertebra > > ribs?

vertebra > (costovertebral/transverse joints) > costal cartilage (sternocostal) > sternum

What movement do sternocostal joints allow?

slight gliding / “give” for respiration

ribs move as unit with sternum

Movement of ribs 1-2

• minimal in quiet respiration

• inspiration: move up / laterally (mainly pump handle)

What are the 2 ways ribs 3-10 move?

• pump handle

• bucket handle

Which movement increases ribs transverse diameter?

bucket handle

(elevation up + lateral)

Which movement increases the thorax’s anteroposterior diameter?

pump handle

Describe the movement of the floating ribs?

ribs 11-12

• small movement permissed in all directions

• *depressed in inspiration! by quadratus lumborum to form fixed point for diaphragm

Which way do the fibers of each intercostal muscle run?

1) external- hand in pocket (grabbing something out pulling up/out)

2) internal- opposite of ^ (originate inf Insert sup pull down/in)

3) innermost- vertical (origin infer, insertion superior- pull down- depress ribs)

What is the action of each intercostal muscle?

1) external- elevation / inspiration

2) internal - depression / exhalation

3) innermost - depression / exhilation

What muscles form the “anterior thoracic wall”?

• intercostals (3)

• Transversus Thoracis

Transversus Thoracis

(OIA)

(spiderman muscle ‘picturing him pulling ship’)

O: post sruface lower sternum + xyphoid process (thats where spidy stand)

I: (‘webs’) to inner surface of costal cartilage 2-6

• rib depression (pull in/down) —expiration

Wat makes up te posterior toracic wall?

serratus posterior (superior + inferior) *the diamond

Serratus posterior superior

(OIA)

O: nuchal lig & SP C7-T3

I: ribs 2-5 lateral to posterior angles

• rib elevation (inspiration)

Serratus Posterior inferior

(OIA)

O: sp T11-12

I: inf boarder ribs 8-12 (lateral to post angles)

• rib depression (expiration)

  

The innermost intercostals assist with what?

rib depression

The transversus thoracis is deep to the sternum.

A. True

B. False

true

What are the walls of the abdomen?

“cube”

• anterior

• lateral

• posterior

• superior / inferior

What muscles make up the anterior wall of the abdomen?

• rectus abdominus

• rectus sheath

  • pyramidalis (within sheath, triangle at bottom tense linea alba)

What innervates most of the abdomen?

ventral rami of thoracic nerves

Rectus Abdominis

(OIAN)

O: pubic crest + symphysis

I: xiphoid process + costal cartilage ribs 5-7

N: ventral rami thoracic nerves

• flex vertebral column

*tendinous structures: linea alba + transverse

What tendinous structures appear in the rectus abdominis?

• linea alba: xiphoid process > pubic symphysis

  • (seperate rectus abdom vertically)

• tendinous intersections: 3 zig zags adherent to ant layer of rectus sheath

What points does the linea alba run between?

xiphoid process > pubic symphysis

What do the 3 tendinous intersections of the rectus abdominis adhere to?

anterior layaer of the rectus sheath

Rectus Sheath

(composition, runs-)

• aponeurotic sheath

• enclose rectus abdom + pyramidalis

• anterior + posterior layer

• ends blended into linea alba (blending with rectus sheath of opp side)

Pyramidalis

(location, action)

• small triangular at base of abdominal sheath

  • pubis > linea alba

• anterior to rect abdom

• tenses linea alba

What muscles make up the lateral wall of the abdomen?

• transversus abdominis

• internal + external obliques

• iliacus

Transversus Abdominis

(OIAN)

“deep core”

• Origin:

  • costal cart 7-12

  • thoracolumbar fascia

  • iliac crest

  • connective tissue under inguinal ligament

• Insertion: linea alba

  • (with combined aponeurosis of intern obliq + pubic crest + pubis)

• ACTION:

  • compress abdominal viscera

  • assist in forced expiration

  • role in Lumbar stabilization

dorsal rami thoracic n

Internal Oblique

(OIA)

(Insert superior - pull down)

• O:

  • lat ½ inguinal lig

  • iliac crest

  • thoracolumbar fascia

• I: (*A)

  • inf boarder rib 10-12

  • linea alba

  • pubic crest

  • pectineal line

• ACTION:

  • support/compress abdominal viscera

  • assist force exp

  • bilat: flex

  • unilat: ipsi lat trunk flex + rot

External Oblique

(OIA)

(put hand in orientation use fingers to pull)

• O: ext surface rib 5-12

• I: (*V)

  • ant ½ iliac crest

  • anoneurosis from 9th cost cart to ASIS, pubic tubercle + linea alba

• ACTION:

  • support / compress abdom viscera

  • assist forced exp

  • bilat: flex spinal column

  • unilat: ipsilat flex, contralat rot

Unilaterally, which muscle is responsible for ipsilateral

rotation:

A. External obliques

B. Internal obliques

C. Transversus abdominis

D. Rectus abdominis

internal obliques

If lying supine and using the rectus abdominis to lift the legs and pelvis off the floor, this movement would be considered what type of chain?

closed chain

(open- lifting feet off floor)

What muscles make up the posterior abdominal wall?

• quadratus lumborum

• psoas major + minor

• iliacus

What muscle fixes rib 12 with inspiration?

quadratus lumborum (working bilaterally)

Quadratus Lumborum

(OIA)

O: iliolumbar ligament + iliac crest

I: lower boarder rib 12 + TP L1-5

• bilat: ext lumbar vert + fix rib 12 with inspiration

• unilat: ipsilat trunk sidebending

Closed vs Open Chain

• closed: extremities fixed, body part in middle move

• open: middle body fixed, extremity move

Diaphragm

(OIAN)

O: circumference of thorax + fibers from xiphoid, cost cart 7-12, L1-3

I: central tendon

• draw central tendon down / forward in inspiration

• relax up in expiration

N: (Phrenic nerve- C3, 4, 5 keep the diaphram alive)

3 parts

What are the 3 parts of the diaphragm?

And where to they each arise from?

1) Sternal - back of xiphoid process

2) costal- internal surface cost cart

3) lumbar- med/lat arcuate ligaments + crura fibers => central tendon

What muscles make up the inferior abdominal wall?

pelvic floor muscles

(unspecified for this class)

What nerves contribute to moving the diaphragm?

Phrenic Nerve

• C3, 4, 5 (keep the diaphragm alive)