Budras_Анатомия лошади

Cervical part

Thoracic part

Lumbar part

Sacral part

C1

C2

C3

C4

C5

C6

C7

C8

T1

T2

T3

T4

T5

T6

T7

T8

T9

T10

T11

T12

T13

T14

T15

T16

T17

T18

L1

L2

L3

L4 L5

L6

S1 S2

S3

S4

Lateral vertebral foramen A

Intervertebral foramen

Cervical

thickening B

Lumbar thickening

C

Lumbosacral foramen

a) At the junction of neck and thorax the VERTEBRAL COLUMN by a deep concavity (as seen from the side) is farthest removed from the dorsal surface of the body. Caudal to this it gradually ascends to be close to the dorsal midline again in the lumbar and pelvic areas. The slanted spinous processes (12) of the thoracic vertebrae increase in length up to T4 (or T5) to form, with the scapulae, the basis of the withers.

Then the spinous processes get steadily shorter, until they have reach 10 cm, which is the length of the anticlinal vertebra (usually

T16) in a medium size horse. This is also the length of the lumbar spinous processes which have a slight cranial inclination.

In young horses the ends of the long thoracic spinous processes of the withers are capped with cartilage, which gradually ossifies with age. The vertebral formula is as follows: C7 (as in all domestic mammals), T18 [17,19], L6 [5,7], S5, Cd (Cy) [15–21]. The square brackets indicate fairly common variations. (The lower case v preceding the segmental designation stands for vertebra.)

I. The spinous process of the cervical vertebrae, except for the second and the last, are poorly developed and absent on C1. The atlas has an alar- (27') and a lateral (28) vertebral foramen (for the first cervical nerve). The axis of older subjects also has a lateral vertebral foramen which transmits the second cervical nerve. Its crest-like spinous process shows evidence caudally that it developed from paired elements. The transverse processes of vertebrae C3–6 present ventral (13') and dorsal (13'') tubercles.

II. The articular surfaces of the articular processes on the thoracic vertebrae undergo a change in direction from a nearly dorsal (horizontal) plane orientation to one that is sagittal. In the more caudal thoracic vertebrae the cranial costal facet (6) on the body is approached and finally touched by the costal facet (14) on the transverse process to form a combined surface for both the head and the tubercle of the rib. In some of these vertebrae the caudal notch is transformed to a lateral vertebral foramen that transmits the spinal nerve.

Costovertebral Articulations

lateral view of vertebrae, caudal view of left ribs. (Cranial, in relation to the vertebrae, is to the left.)

vT8

14

50 46

vT17

14

6

XVII

50 46

III. The transverse processes (13) of the lumbar vertebrae project laterally, and the last two form a joint (or fuse) with each other. This causes the intervertebral foramina to be partitioned into dorsal and ventral openings for the respective primary branches of the spinal nerves. The last lumbar transverse process articulates at its base with the wing of the sacrum with a similar partition of the intervertebral foramen.

The fenestrated lamina nuchae fills the space between the cervical vertebrae and the funiculus. It extends cranioventrally from the latter and from the spinous processes of T2 and T3 and attaches on the spinous processes of all cervical vertebrae except the first.

d) MUSCLES OF THE VERTEBRAL COLUMN (see Table on p. 96).

Cervical vertebrae (C1–7) Thoracic vertebrae (T1–18 [17–19]) Lumbar vertebrae (L1–6 [5–7]) Sacral vertebrae (S1–5)

Caudal vertebrae (Cd1–x) (Cy1–x) Body (1)

Ventral crest (2) Cranial extremity (3) Caudal extremity (4)

Caudal costal facet [C7, T] (5) Cranial costal facet [T] (6)

Vertebral canal (7) Arch (8)

Intervertebral foramen (9) Cranial notch (10) Caudal notch (11)

Spinous process (12) Transverse process (13)

Ventral tubercle [C3–6] (13') Dorsal tubercle [C3–6] (13'') Costal facet [T] (14)

Transverse foramen [C1–6] (15) Cranial articular process (16) Caudal articular process (17) Costal process [C3–6, L] (18)

Mamillary process [T–S] (20)

32

(Lateral view)

Wing (26)

Alar foramen (17')

Lateral vertebral foramen (28) Dorsal arch (29)

Ventral arch (30)

Axis [C2] (31)

Lateral vertebral foramen (31') Dens (32)

Sacrum [S1–5]

Wing of sacrum [S1] (33) Notch (foramen) of wing (33') Auricular surface (34)

Lateral sacral crest (36) Promontory (38)

Dorsal sacral foramen (39) Ventral sacral foramen (40)

16

10

3

13

13'

vC2

12

9

45

49

52 41

42

53

3

vC1

A'

A''

A

B

(lateral)

C'

C

12

vT18

(Dorsolateral view)

a) DEEP SHOULDER-GIRDLE MUSCLES:

The rhomboideus consists of two parts. The cervical (28) is cranial to the scapula, on which it attaches, while the thoracic part (28') is at the level of the sapula and lies deep to scapular cartilage.

The pectoralis profundus (25') ascends from its origin on the sternum (and vicinity) to the medial and lateral tubercles of the humerus. The subclavius (25), also one of the pectoral muscles, arises from the cranial part of the sternum and ascends craniomedial to the shoulder joint and supraspinatus muscle to end on the cranial border of the scapula.

The serratus ventralis (27, 27'), like the rhomboideus, consists of cervical and thoracic parts. Both parts converge on the upper part of the medial scapular surface; the cervical part with caudodorsal, mostly fleshy bundles, the thoracic with vertical and craniodorsal bundles and tendinous sheets.

b) VENTRAL NECK MUSCLES:

Sternohyoideus (19) and sternothyroideus (20) ascend ventral to the trachea from a common origin on the manubrium of the sternum. They divide in midneck to seek their separate insertions on the basihyoid, and the thyroid cartilage of the larynx, respectively. Right and left muscles in the caudal half of the neck are fused in the midline, and the sternohyoidei remain so to their attachment on the basihyoid. The omohyoideus (13) arises from the subscapular fascia just dorsal to the shoulder joint. On its way to the basihyoid it very obliquely crosses the deep surface of the ext. jugular vein, after which it fuses with the sternohyoideus.

c) The VISCERAL SPACE OF THE NECK:

The space occupied by trachea, esophagus, and the vessels and nerves accompanying them is formed ventrally by the strap muscles

arising from the manubrium (sternohyoideus, —thyroideus, and

—cephalicus); laterally by the omohyoideus and the sternocephalicus again; and dorsally by the longus colli and capitis, muscles of the vertebral column. The trachea (21), the largest occupant of the visceral space holds a median position and, depending on the level, is related to all muscles bounding the visceral space. Its cartilages overlap dorsally, and their ends are joined by the tracheal muscle that lies in the dorsal wall of the tube between the mucous membrane and the cartilages. The common carotid artery (16) lies dorsolateral to the trachea at the cranial end of the neck, while near the thorax it has descended into a ventrolateral position. (An internal

jugular vein is very small or absent.) The esophagus (14) at the cra- 4 nial end of the neck is dorsal to the trachea; in midneck it lies to the

left of the trachea; shortly before the thoracic inlet it can even be ventral to the trachea, but as it passes into the thorax it regains its dorsal position in respect of the trachea. The vagosympathetic trunk (17) lies dorsomedial, and the recurrent laryngeal nerve (15) ventromedial to the common carotid artery.

d) LYMPHATIC STRUCTURES:

The supf. cervical lymph nodes (7), imbedded in fat, lie against the cranial surface of the subclavius and are covered laterally by the cleidomastoideus. They drain supf. structures of the neck, thorax, and forelimb. Their efferents pass directly to the veins at the thoracic inlet, or indirectly via the caudal deep cervical nodes.

The cranial (12), middle (18), and caudal (23) deep cervical lymph nodes are grouped along the tracheal (lymph) duct that conveys lymph from the head to the veins at the thoracic inlet. The cranial group is confluent with the medial retropharyngeal nodes. The especially large nodes of the caudal group are occasionally difficult to distinguish from the supf. cervical nodes and from the cranial mediastinal nodes.

For the dissections on this page the intercostal muscles and the ribs

(except ribs 9 and 15–18) were removed without disturbing the insertion of the diaphragm. In the upper dissection on the opposite page the right lung was also removed. Except for size and the number of ribs, the thoracic cavity of the horse follows the general mammalian pattern. The few species-specific features are noted in the text.

a)The cranial portion of the THORAX is covered laterally by the skeleton and muscles of shoulder and arm, preventing clinical examination by auscultation and percussion of the organs within— unless the forelimb is pulled forward. The latissimus dorsi and the flat abdominal and cutaneous muscles cover the ribs and intercostal muscles caudal to the forelimb and are part of the thoracic wall.

b)RESPIRATORY MUSCLES (see Tables on Mylogy on p. 98).

I. Expiratory muscles

II.Inspiratory muscles, including the diaphragm, the principal inspiratory muscle.

The diaphragm forms the boundary between thoracic and abdominal cavities. Its insertion on the thoracic wall extends in a gentle curve from the 8th and 9th costal cartilages, across the costochondral junctions of the 9th–15th ribs, to the middle of the 18th rib where it turns craniomedially to end at the vertebral end of the last

(17th) intercostal space. In the median plane the diaphragm bulges forward to the level of the 7th rib, and thus is almost opposite the olecranon in the standing animal. The three openings of the diaphragm, beginning dorsally, are the aortic hiatus between right and left crura, for the aorta; the esophageal hiatus in the (larger) right crus, for the esophagus; and the caval foramen (5) in the tendinous center, for the caudal vena cava. Surrounding the tendinous center is the muscular part divisible into sternal (7), costal (6), and lumbar (3) segments by which the diaphragm is attached at its periphery.

c)The two PLEURAL SACS line the thoracic cavity including the diaphragm and contact each other in the median plane to form the mediastinum. Where the pleura that covers the diaphragm reflects on itself to become the costal pleura that lines the ribs, is the line of pleural reflection that follows the attachment of the diaphragm.

Craniodorsal to the line of pleural reflection, diaphagmatic (8) and costal (9) pleurae are in contact and are separated by a potential space known as the costodiaphragmatic recess (10).

d)The MEDIASTINUM contains the heart and all other thoracic organs except the lungs (which reside within the pleural sacs) and the caudal vena cava (e) which indents the right pleural cavity supported by the caval fold (f).

In regions where the mediastinum contains no organs it is relatively thin and may be fenestrated as a result of an underdeveloped or degenerated lamina propria that separates the two pleural layers.

Fenestrations are seen mainly caudal to the heart. This part of the mediastinum is pushed far over to the left because of the greater mass of the right lung.

e)The ESOPHAGUS (14) traverses the mediastinum from the thoracic inlet to the diaphragm. At the inlet it lies still a little to the left, but still in the cranial mediastinum it reaches the median plane dorsal to the trachea. In this region its muscular coat changes from striated to smooth muscle which may be seen in fresh specimens by a color change.

f)The LUNGS reflect the general shape of the thoracic cavity and are long and laterally compressed cranially. The root of the lung, fully visible when one lung is removed, lies opposite the 6th rib and includes the principal bronchus (A) and the pulmonary artery and veins (w, x). The “lung field” is the projection of the lung on the surface of the animal, caudal to the forelimb. It is roughly triangular, bounded dorsally by the back muscles and caudoventrally by the basal border of the lung. The latter curves from the costochondral junction of the 6th rib through the middle of the 11th rib to the edge of the back muscles at the 16th intercostal space. The lung can be percussed and auscultated within the lung field, though respiratory

Right lung in situ

IX

sounds cease a few cm proximal to the thin basal border so that the “audible” lung field is slightly smaller than the projection.

The right lung is larger than left because it carries the centrally located accessory lobe (25). Interand intralobar fissures are absent so that cranial (18) and caudal (26) lobes are separated only by the wide cardiac notch (22). Part of the mediastinal surface of both lungs fuses in an elongated area caudal to the hilus. The lobulation of the equine lungs is indistinct.

Left lung in situ

IX

g) Most of the LYMPH NODES of the thorax, as in other areas, consist of aggregates of small nodes. The right (19), left (20), and middle (23) tracheobronchial nodes surround the tracheal bifurcation. Nearby pulmonary nodes (24) are inconstant and are covered by lung tissue. The cranial mediastinal nodes (15) continue the caudal deep cervical nodes within the thorax. Middle mediastinal nodes (16) lie dorsal to the heart, and the caudal mediastinal nodes (13) occupy the caudal mediastinum between aorta and esophagus. Inconstant cranial sternal lymph nodes (17) lie cranial to the internal thoracic vessels and are not easily distinguished from the cranial mediastinal nodes. There are also inconstant caudal sternal lymph nodes where the diaphragm attaches to the sternum. The intercostal lymph nodes (11) occupy the dorsal ends of the intercostal spaces

3–16, while the paired thoracic aortic nodes (12) lie dorsal to the aorta opposite the 3rd to the 17th thoracic vertebrae; they are more numerous on the left since the right ones are often absent at the level of the 9th–14th vertebrae.

The efferent lymphatics arising from the nodes in the thoracic cavity communicate variously and either join the veins at the thoracic inlet or the cranial segment of the thoracic duct (1). The latter, having arisen from the cisterna chyli, accompanies the aorta forward and crosses the left face of the trachea before ending on one of the veins at the thoracic inlet, usually the cranial vena cava.