Frontal part of an animal's body, between its head and abdomen
The
thorax
(
pl.
:
thoraces
or
thoraxes
)
[1]
or
chest
is a part of the
anatomy
of mammals and other
tetrapod
animals located between the
neck
and the
abdomen
.
[2]
[3]
In
insects
,
crustaceans
, and the extinct
trilobites
, the thorax is one of the three main
divisions
of the creature's body, each of which is in turn composed of multiple segments.
The human thorax includes the
thoracic cavity
and the
thoracic wall
. It contains organs including the
heart
,
lungs
, and
thymus
gland, as well as muscles and various other internal structures. Many diseases may affect the chest, and one of the most common symptoms is
chest pain
.
Etymology
[
edit
]
The word thorax comes from the
Greek
θ?ραξ
th?rax
"
breastplate
,
cuirass
,
corslet
"
[4]
via
Latin
:
thorax
.
[5]
Human thorax
[
edit
]
Structure
[
edit
]
In humans and other
hominids
, the thorax is the chest region of the body between the
neck
and the
abdomen
, along with its internal
organs
and other contents. It is mostly protected and supported by the
rib cage
,
spine
, and
shoulder girdle
.
Contents
[
edit
]
The contents of the thorax include the
heart
and
lungs
(and the
thymus
gland); the
major
and
minor
pectoral muscles,
trapezius muscles
, and
neck
muscle; and internal structures such as the
diaphragm
, the
esophagus
, the
trachea
, and a part of the
sternum
known as the
xiphoid process
. Arteries and veins are also contained ? (
aorta
,
superior vena cava
,
inferior vena cava
and the
pulmonary artery
);
bones
(the shoulder socket containing the upper part of the
humerus
, the
scapula
,
sternum
,
thoracic portion of the spine
,
collarbone
, and the rib cage and
floating ribs
).
External structures are the
skin
and
nipples
.
The chest
[
edit
]
In the
human body
, the region of the thorax between the
neck
and
diaphragm
in the front of the body is called the chest. The corresponding area in an animal can also be referred to as the chest.
The shape of the chest does not correspond to that part of the
thoracic skeleton
that encloses the
heart
and
lungs
. All the breadth of the shoulders is due to the shoulder girdle, and contains the
axillae
and the heads of the
humeri
. In the middle line the
suprasternal notch
is seen above, while about three fingers' breadth below it a transverse ridge can be felt, which is known as the
sternal angle
and this marks the junction between the manubrium and body of the
sternum
. Level with this line the second ribs join the sternum, and when these are found the lower ribs can often be counted. At the lower part of the sternum, where the seventh or last true ribs join it, the
ensiform cartilage
begins, and above this there is often a depression known as the pit of the
stomach
.
Bones
[
edit
]
The bones of the thorax, called the "thoracic skeleton" is a component of the
axial skeleton
.
It consists of the
ribs
and
sternum
. The ribs of the thorax are numbered in ascending order from 1?12. 11 and 12 are known as floating ribs because they have no anterior attachment point in particular the cartilage attached to the sternum, as 1 through 7 are, and therefore are termed "floating". Whereas ribs 8 through 10 are termed false ribs as their costal cartilage articulates with the costal cartilage of the rib above. The thorax bones also have the main function of protecting the heart, lungs, and major blood vessels in the thorax area, such as the
aorta
.
Anatomical landmarks
[
edit
]
The anatomy of the chest can also be described through the use of
anatomical landmarks
. The
nipple
in the male is situated in front of the fourth rib or a little below; vertically it lies a little external to a line drawn down from the middle of the
clavicle
; in the female it is not so constant. A little below it the lower limit of the great pectoral muscle is seen running upward and outward to the axilla; in the female this is obscured by the
breast
, which extends from the second to the sixth rib vertically and from the edge of the sternum to the mid-axillary line laterally. The female nipple is surrounded for half an inch by a more or less pigmented disc, the
areola
. The apex of a normal heart is in the fifth left intercostal space, three and a half inches from the mid-line.
Clinical significance
[
edit
]
Different types of
diseases
or conditions that affect the chest include
pleurisy
,
flail chest
,
atelectasis
, and the most common condition, chest pain. These conditions can be hereditary or caused by
birth defects
or
trauma
. Any condition that lowers the ability to either breathe deeply or to
cough
is considered a chest disease or condition.
Injury
[
edit
]
Injury to the chest (also referred to as chest trauma, thoracic injury, or thoracic trauma) results in up to
1
/
4
of all deaths due to
trauma
in the United States.
[6]
The major
pathophysiologies
encountered in blunt chest trauma involve derangements in the flow of air, blood, or both in combination. Sepsis due to leakage of alimentary tract contents, as in esophageal perforations, also must be considered. Blunt trauma commonly results in chest wall injuries (e.g., rib fractures). The pain associated with these injuries can make breathing difficult, and this may compromise ventilation. Direct lung injuries, such as pulmonary contusions (see the image below), are frequently associated with major chest trauma and may impair ventilation by a similar mechanism.
Pain
[
edit
]
Chest pain
can be the result of multiple issues, including
respiratory
problems,
digestive
issues, and
musculoskeletal
complications. The pain can trigger cardiac issues as well. Not all pain that is felt is associated with the heart, but it should not be taken lightly either. Symptoms can be different depending on the cause of the pain.
[7]
While cardiac issues cause feelings of sudden pressure in the chest or a crushing pain in the back, neck, and arms, pain that is felt due to noncardiac issues gives a burning feeling along the digestive tract or pain when deep breaths are attempted. Different people feel pains differently for the same condition. Only a patient truly knows if the symptoms are mild or serious.
Chest pain may be a symptom of
myocardial infarctions
('heart attack'). If this condition is present in the body, discomfort will be felt in the chest that is similar to a heavy weight placed on the body. Sweating, shortness of breath,
lightheadedness
, and
irregular heartbeat
may also be experienced. If a heart attack occurs, the bulk of the damage is caused during the first six hours, so getting the proper treatment as quickly as possible is important. Some people, especially those who are elderly or have diabetes, may not have typical chest pain but may have many of the other symptoms of a heart attack. It is important that these patients and their caregivers have a good understanding of heart attack symptoms.
Non-cardiac causes of chest pain
[
edit
]
Just like with a heart attack, not all chest pain is caused by conditions involving the
heart
. Chest wall pain can be experienced after an increase in activity. Persons who add exercise to their daily routine generally feel this type of pain at the beginning.
[
citation needed
]
It is important to monitor the pain to ensure that it is not a sign of something more serious. Pain can also be experienced in persons who have an upper respiratory
infection
. This virus is also accompanied by a fever and cough.
Shingles
is another viral infection that can give symptoms of chest or rib pain before a rash develops. Injuries to the rib cage or sternum is also a common cause of chest pain. It is generally felt when deep breaths are taken or during a cough.
Atelectasis
[
edit
]
Another non-cardiac cause of chest pain is
atelectasis
. It is a condition that occurs when a portion of the lung collapses from being airless. When bronchial tubes are blocked, this condition develops and causes patients to feel shortness of breath. The most common cause of atelectasis is when a bronchi that extends from the windpipe is blocked and traps air. The blockage may be caused by something inside the
bronchus
, such as a plug of mucus, a
tumour
, or an inhaled foreign object such as a coin, piece of food, or a toy.
[8]
It is possible for something outside of the bronchus to cause the blockage.
Pneumothorax
[
edit
]
Pneumothorax
is the condition where air or gas can build up in the
pleural
space. It can occur without a known cause or as the result of a lung disease or acute lung injury.
[9]
The size of the pneumothorax changes as air or gas builds up, so a medical procedure can release the pressure with a needle. If it is untreated, blood flow can be interrupted and cause a drop in blood pressure known as tension pneumothorax. It is possible for smaller cases to clear up on their own. Symptoms of this condition are often felt only on one side of the lung or as a shortness of breath.
Other animals
[
edit
]
In tetrapods
[
edit
]
In
mammals
, the thorax is the region of the body formed by the
sternum
, the thoracic
vertebrae
, and the
ribs
. It extends from the neck to the
diaphragm
, and does not include the
upper limbs
. The
heart
and the
lungs
reside in the
thoracic cavity
, as well as many
blood vessels
. The inner organs are protected by the
rib cage
and the sternum. Thoracic vertebrae are also distinguished in
birds
, but not in
reptiles
.
In arthropods
[
edit
]
The trilobite body is divided into three major sections, a cephalon with eyes, mouthparts and sensory organs such as antennae, a thorax of multiple similar segments (that in some species allowed them to roll up into a ball), and a pygidium, or tail section.
In the worker ant, the abdomen consists of the
propodeum
fused to the thorax and the
metasoma
, itself divided into the narrow
petiole
and bulbous
gaster
.
In
insects
,
crustaceans
, and the extinct
trilobites
, the thorax is one of the three main
divisions
of the creature's body, each of which is in turn composed of multiple segments. It is the area where the
wings
and legs attach in insects, or an area of multiple articulating plates in trilobites. In most insects, the thorax itself is composed of three segments; the
prothorax
, the
mesothorax
, and the
metathorax
. In extant insects, the prothorax never has wings, though legs are always present in adults; wings (when present) are restricted to at least the mesothorax, and typically also the metathorax, though the wings may be reduced or modified on either or both segments. In the
apocritan
Hymenoptera
, the first abdominal segment is fused to the metathorax, where it forms a structure known as the
propodeum
. Accordingly, in these insects, the functional thorax is composed of four segments, and is therefore typically called the
mesosoma
to distinguish it from the "thorax" of other insects.
Each thoracic segment in an insect is further subdivided into various parts, the most significant of which are the dorsal portion (the
notum
), the lateral portion (the
pleuron
; one on each side), and the ventral portion (the
sternum
). In some insects, each of these parts is composed of one to several independent exoskeletal plates with membrane between them (called
sclerites
), though in many cases the sclerites are fused to various degrees.
Human thorax images
[
edit
]
See also
[
edit
]
References
[
edit
]
External links
[
edit
]
Look up
thorax
in Wiktionary, the free dictionary.
|
---|
Head and neck
| |
---|
Arm and axilla
| |
---|
Chest
| |
---|
Abdomen
| |
---|
Leg
| |
---|