Skeletal System (Part 3) - Vertebrae, ribs and sternum

Summary

This module discusses the vertebral formula, structure, and classification of the vertebrae, ribs, and sternum in animals, with a focus on dogs. It explains the arrangement of vertebrae (cervical, thoracic, lumbar, sacral, caudal), the features of each type, and their role in supporting the body. The rib structure and their articulation with the thoracic vertebrae and sternum are also covered. Notable sections include descriptions of the atlas, axis, anticlinal vertebra, and the differences between sternal and floating ribs. A quiz is offered at the end of the module.

Takeaways

• 📚 The vertebral formula of a dog is C7, T13, L7, S3, and Ca 20-24, meaning 7 cervical, 13 thoracic, 7 lumbar, 3 sacral, and 20-24 caudal vertebrae.
• 🦴 Vertebrae are irregular bones that form the vertebral column, extending from the skull to the tail.
• 🦓 The vertebrae are grouped by location: cervical (neck), thoracic (chest), lumbar (loin), sacral (pelvic), and caudal (tail).
• 🐕‍🦺 A typical vertebra has a body, an arc, and several processes; the sixth cervical vertebra is used as an example.
• 🏗️ The first cervical vertebra, the atlas, supports the head, and the second cervical vertebra, the axis, forms a pivot joint with the atlas.
• 🔧 The thoracic vertebrae are characterized by tall spinous processes and articulate with the ribs, with T11 serving as the anticlinal vertebra in dogs.
• 🐾 There are 13 pairs of ribs in dogs, corresponding to the number of thoracic vertebrae, with 9 true ribs, 3 false ribs, and 1 floating rib.
• 🧩 The sternum is composed of 8 fused bones called sternebrae and is divided into the manubrium, body, and xiphoid process.
• 🔩 The ribs are divided into different types based on their attachment to the sternum: true ribs, false ribs, and floating ribs.
• 🔍 Key processes on vertebrae include spinous, transverse, and articular processes, with additional features like transverse foramina in cervical vertebrae.

Q & A

What is the vertebral formula of a dog?

The vertebral formula of a dog is C7, T13, L7, S3, Ca20-24. This means there are 7 cervical, 13 thoracic, 7 lumbar, 3 sacral, and 20-24 caudal vertebrae.

Where are the cervical vertebrae located, and how many are there in a dog?

The cervical vertebrae are located in the neck region, and there are 7 cervical vertebrae in a dog.

What are the key characteristics of thoracic vertebrae?

Thoracic vertebrae are characterized by tall spinous processes, short bodies, and transverse processes. They also articulate with the ribs.

What is the function of the atlas (C1) in the vertebral column?

The atlas, or C1, supports the head and connects it with the rest of the body. It is morphologically unique, lacking a spinous process and having wing-like transverse processes.

How do the ribs articulate with the vertebral column in dogs?

Ribs articulate with the thoracic vertebrae. The head of the rib connects with the costal fovea on the body of the vertebra, while the tubercle of the rib connects with the transverse fovea on the transverse process of the vertebra.

How are sternal and asternal ribs different in dogs?

Sternal ribs, also called true ribs, directly articulate with the sternum via costal cartilages, while asternal ribs, or false ribs, do not directly attach to the sternum and are instead fused into the costal arch.

What is the role of the sacrum in the vertebral column?

The sacrum is formed by the fusion of sacral vertebrae and articulates with the hip bones to form the sacroiliac joint, providing support to the pelvis.

What are the typical components of a vertebra?

A typical vertebra consists of a body, an arc (composed of the lamina and pedicle), and various processes, including spinous, transverse, and articular processes.

What is the anticlinal vertebra, and where is it located in a dog?

The anticlinal vertebra in a dog is T11, characterized by a vertically oriented spinous process, in contrast to the adjacent thoracic vertebrae that have spinous processes angled cranially or caudally.

What is the purpose of the hemal arches in the caudal vertebrae of dogs?

Hemal arches are bony structures found on the ventral surface of the 4th to 6th caudal vertebrae in dogs. They protect the median caudal artery.

Outlines

00:00

🦴 Introduction to Vertebrae and Skeletal Anatomy

This paragraph introduces the vertebral column, ribs, and sternum, explaining their location and function in the body. It describes how the vertebrae are classified into different groups based on their location (cervical, thoracic, lumbar, sacral, and caudal) and highlights the vertebral formula for a dog: C7, T13, L7, S3, and Ca20-24. The paragraph also mentions that vertebrae are classified as irregular bones, sharing a common structure with a body, arc, and processes. It concludes by describing the basic parts of a typical vertebra and their respective roles.

05:02

📏 Anatomical Characteristics of the Atlas and Axis

This paragraph focuses on the first two cervical vertebrae—the atlas and axis. The atlas holds the head and is unique in its structure, lacking a spinous process and featuring modified wings. The axis, on the other hand, has a tooth-like projection called the 'dens,' which forms a pivot joint with the atlas. Additionally, the thoracic vertebrae are discussed, characterized by their tall spinous processes and articulation with the ribs, with specialized structures for rib attachment, such as the transverse fovea and costal fovea.

10:04

🐕 Overview of Rib Types and Sternum Structure

This paragraph explains the structure and function of the ribs and sternum, highlighting that there are 13 pairs of ribs corresponding to the number of thoracic vertebrae. Ribs are classified as sternal (true ribs), asternal (false ribs), and floating ribs, with dogs having 9 pairs of sternal ribs and 3 pairs of asternal ribs. The sternum is described as consisting of eight individual bones (sternebrae), with the manubrium as the first segment and the xiphoid process as the last. The paragraph ends with a brief mention of a quiz on this section and an introduction to the next module covering the bones of the thoracic limb.

Keywords

💡Vertebrae

Vertebrae are the individual bones that form the vertebral column or backbone. In the context of the video, they are classified based on their location: cervical, thoracic, lumbar, sacral, and caudal. These bones protect the spinal cord and provide structural support for the body. Examples include the cervical vertebrae in the neck and the thoracic vertebrae in the chest region.

💡Vertebral Formula

The vertebral formula is a shorthand used to represent the number of each type of vertebra in an animal. For dogs, the formula is C7, T13, L7, S3, Ca 20-24, meaning they have 7 cervical, 13 thoracic, 7 lumbar, 3 sacral, and 20 to 24 caudal vertebrae. This formula helps identify the anatomical structure of the vertebral column.

💡Cervical Vertebrae

Cervical vertebrae are the vertebrae located in the neck region. In dogs, there are seven cervical vertebrae (C1 to C7), with C1 (atlas) and C2 (axis) being the most distinct. The cervical vertebrae support the skull and allow head movement, with unique structures like the transverse foramen in mammals.

💡Atlas and Axis

The atlas (C1) and axis (C2) are the first two cervical vertebrae. The atlas holds the head and allows it to nod, while the axis has a tooth-like projection called the dens that forms a pivot joint with the atlas, enabling head rotation. These bones are vital for the mobility and support of the head.

💡Thoracic Vertebrae

Thoracic vertebrae are found in the chest area and articulate with the ribs. In dogs, there are 13 thoracic vertebrae, and their spinous processes are tall and oriented caudally. They support the rib cage, protecting vital organs like the heart and lungs. The T11 vertebra is known as the anticlinal vertebra, marking a change in spinous process orientation.

💡Lumbar Vertebrae

Lumbar vertebrae are located in the lower back or loin region, characterized by large, flat transverse processes that project laterally. In dogs, there are 7 lumbar vertebrae, and they provide support for the abdominal organs while also allowing for flexible movement in the lower back.

💡Sacral Vertebrae

Sacral vertebrae are fused bones found in the pelvic region. In dogs, there are three sacral vertebrae, which form the sacrum. The sacrum articulates with the hip bones to form the sacroiliac joint, which is important for stability and movement of the hind limbs.

💡Ribs

Ribs are long, curved bones that form the lateral walls of the thorax, protecting organs such as the heart and lungs. In dogs, there are 13 pairs of ribs, which correspond to the thoracic vertebrae. They are classified into sternal (true ribs), asternal (false ribs), and floating ribs based on their connection to the sternum.

💡Sternum

The sternum is a series of bones located at the ventral midline of the thorax, providing attachment for the costal cartilages of the ribs and the pectoral muscles. It consists of eight bones called sternebrae, which fuse with age. The first sternebra is the manubrium, and the last is the xiphoid process.

💡Caudal Vertebrae

Caudal vertebrae are found in the tail of the dog. Their number varies from 20 to 24, becoming progressively smaller toward the tail's tip. These bones support the tail's structure and movement, and in some vertebrae, hemal arches protect the median caudal artery.

Highlights

Introduction to the vertebrae, ribs, and sternum in the skeleton.

The vertebral formula of a dog includes seven cervical, 13 thoracic, seven lumbar, and three sacral vertebrae, with 20 to 24 caudal vertebrae.

Vertebrae are classified as irregular bones due to their shape, but share common structural parts.

The cervical vertebrae, located in the neck region, include C1 (atlas) and C2 (axis), which are atypical compared to the others.

C1, or the atlas, supports the head and lacks a spinous process, with transverse processes modified into wings.

C2, or the axis, has a tooth-like projection called the 'dens' or 'odontoid process,' which articulates with the atlas to form a pivot joint.

Thoracic vertebrae are characterized by tall spinous processes, short bodies, and articulate with the ribs.

The anticlinal vertebra in a dog is T11, where the orientation of the spinous process changes direction.

Lumbar vertebrae, located in the loin area, have large, flat transverse processes and include accessory processes.

The sacrum, composed of fused sacral vertebrae, forms the sacroiliac joint by articulating with the hip bones.

Caudal vertebrae, forming the tail, range from 6 to 24 in number and become rod-like distally.

Ribs are long, curved bones that form the lateral walls of the thorax, and the number of ribs corresponds with the thoracic vertebrae.

In dogs, there are nine pairs of sternal ribs and three pairs of asternal (false) ribs.

The sternum, made up of eight segments called sternebrae, forms the ventral part of the thorax and supports the ribs.

The manubrium is the first and longest segment of the sternum, while the xiphoid process is the last segment, holding the xiphoid cartilage.

Transcripts

welcome to part three of module two

after identifying the bones of the head

let us now continue discussing other

parts of the actual skeleton

like the vertebrae the ribs and the

sternum

at the end of this presentation you

should be able to write the vertebral

formula of dog

identify the total number of free pairs

present

and its relation to the number of sterne

braid

first let us see the general arrangement

of the vertebrae

ribs and sternum in the body of an

animal

the vertebrae are located at the dorsal

midline

the rib forms a lateral bony structure

supporting the thorax

while the sternum are located at the

ventral midline

the vertebral column is composed of a

number of unpaired bones

called vertebrae arranged in a series

along the midline of the body

and extending from the base of the skull

to the tip of the tail

the vertebrae can be grouped based on

their location

cervical vertebrae are located at the

neck region

the thoracic vertebrae are located at

the level of the chest

lumbar vertebrae are those present at

the loin area

sacral vertebrae are the fused vertebrae

at the level of the pelvic area

and finally the caudal vertebrae which

supports the tail

vertebral formula represents the number

of specific

vertebrae in an animal the number is

constant except for the caudal vertebrae

take note that the number varies per

species

in dog the vertebral formula is c7

t13 l7 s3

ca 20-24 this means

that the dog has seven cervical

vertebrae

13 thoracic vertebrae 7 lumbar vertebrae

3 sacral vertebrae and around 20 to 24

caudal vertebrae

remember that vertebrae are classified

as irregular bones because of their

irregular shape

however most of the vertebrae have the

basic parts in common

a typical vertebra has a body an arc

and number of processes let's identify

the parts of a vertebra

this is the sixth cervical vertebra

the body is a cylindrical mass forming

the ventral part of the vertebra

and the floor of the vertebral foramen

it is

convex cranially as shown here and

concave

caudally the vertebral art completes the

vertebral foramen dorsally

the arc is composed of a lamina and

pedicle

the lamina forms the roof of the ark

while the pedicle forms the wall of the

arc

on the average there are seven processes

present at the vertebral arc

there is a single spinous process that

projects

dorsally from the arc of the vertebra

the paired transverse processes project

laterally from the arc

there are also four articular processes

two cranial and two codal articular

processes

they form joints between adjacent

vertebrae

the vertebral foramen is the space

formed by the vertebral arc and the body

the vertebral foramina of all vertebrae

form the vertebral canal

the paired transverse foramen is an

opening

present at the transverse process

through which vertebral

artery passes there are seven

cervical vertebrae in mammals these are

the vertebrae at the neck region

they are characterized by a massive

appearance and by the presence of

transverse foramen as discussed

previously

this slide shows examples of the

cervical vertebrae

note that they have different views of

presentation

c1 or atlas and c2 or axis

are considered as atypical meaning they

are not

similar in appearance with the rest of

the cervical vertebrae

third to fifth cervical vertebrae are

almost the same with the sixth cervical

vertebra

the seventh cervical vertebra locks the

transverse foramen

and has a tall spinous process we will

just

focus on the first and second cervical

vertebrae

the first cervical vertebra is the atlas

the name of this bone was derived from

the greek mythology character atlas

which was given the task of holding up

the heavens

the same with the first cervical

vertebra it is holding the head in place

with the rest of the body

morphologically the atlas is a typical

it does not follow the same structures

present in most vertebrae

some books considered the body of atlas

to be absent

but in some it is described as a thin

structure

forming the ventrum of the bone this is

in contrast to the bulky body of other

vertebrae

here is a dorsal and caudal view of the

atlas

take note that it lacks spinous process

the transverse processes are modified

into wings

it has a transverse foramen and lateral

vertebral foramen

the alar foramen is modified into our

notch

the presence of allah notch is

characteristic of a dog atlas

the axis or epistrophuse is the second

cervical vertebra

it has a tooth like bony projection at

the cranial end

called dense or odontoid process which

articulate with the atlas forming a

pivot joint

take note that it has a large ridge-like

spinous process

the thoracic vertebra is characterized

by the tall spinous process short body

and transverse processes the thoracic

vertebrae articulate with the rib

thus it has structures specialized for

such

the transverse fovea is a plane surface

at the transverse process of the

vertebra

that articulates with the tubercle of

the rib

on the other hand the costal fovea is a

plane surface that articulates with the

head of the ribs

they are located at the body of the

vertebra

in dogs there are 13 number of repairs

look at this schematic drawing of the

thoracic vertebrae of dog

observe that the spinous processes are

oriented caudally

until one spinous process is vertically

inclined

this vertebra is called the anticlinal

vertebra

in contrast the spinous processes of the

vertebrae cuddle to the anticlinal

vertebra

is oriented cranially the anticlinal

vertebra of dog is t11

as you recall the lumbar vertebrae are

located at the loin area

the lumbar vertebrae can be

distinguished from the rest of the

vertebrae

because of its large flat or plate-like

transverse

processes that project laterally

in addition to other processes present

in other vertebrae

the lumbar vertebrae has an accessory

process

note that this are present from the mid

thoracic vertebrae to the lumbar

vertebrae

this should not be confused with a

ruptured intervertebral disc

they also have mammiliary process which

are present at the cranial articular

processes

and the processes of the three sacral

vertebrae fuse to form the sacrum

here is a lateral dorsal

and ventral view of the sacrum

the median sacral crest is the fused

spinous processes

present at the dorsal surface of the

suck room

the wing forms the lateral parts of the

sacrum

that articulates with the hip bone to

form the sacroiliac joint

you can also observe paired openings

seen at the dorsal and ventral views

this are the dorsal and ventral sacral

foramina

these are for the passage of the spinal

nerves

the promontory is a transverse ridge at

the cranioventral part of the base

this can be best seen on a cranial or

ventral view

the vertebrae of the tail has an average

number of 20

but may range between 6 to 24.

they became smaller distally until it

become a rod-like structure

hemal arches are present as a separate

bone that articulates with the ventral

surface of the fourth

fifth and sixth caudal vertebrae in life

this structure is protecting the median

caudal artery

again here are the segments of the

vertebral column

cervical thoracic lumbar

sacral and caudal vertebrae

take note that in writing the vertebral

formula

it must be written in chronological

order

after finishing the bones of the

vertebral column

let us now discuss the bones of the

thorax

this is a bony cavity formed by the

sternum

ribs costal cartilages

and the bodies of the thoracic vertebrae

this bones support and protect the soft

tissues and organs of the thoracic

cavity

like the lungs and the heart ribs

are longed curved bone forming the

lateral walls of the thorax

usually the number of pairs of ribs is

the same with the number of the thoracic

vertebrae

remember that the thoracic vertebrae is

13 in number

thus the number of rib bears is also 13.

ribs can be classified depending on

their articulation with the sternum

sternal or true ribs truribs articulates

with the sternum by means of its costal

cartilage

the costal cartilages are cartilaginous

cylindrical

distal continuation of the bony rib

sternal ribs are also known as immobile

ribs

there are nine pairs of sternal ribs in

dog

asternal or false ribs have no direct

attachment with the sternum

however their cartilages are fused to

form the costal arc

they are also called the respiratory rib

because they are mobile

there are three pairs of external ribs

in dog

here is the coastal ark it is formed by

the costal cartilages

of the 10 11 and 12 rib

with the last segment of the sternum

the last is the floating rib it has no

connection with the sternum

and no cartilage is present it is

usually the last stream

and found only in dog and man

let us then discuss the parts of a rib

the head of the rib articulates with the

costal fovea of the thoracic vertebrae

the neck of the rib connects the head to

the body

or shaft of the rib the tubercle of the

rib

is a bony small prominence lateral to

the head

that articulates with the transverse

fovea of the thoracic vertebrae

the sternum forms the ventrum of the

bony thorax

and gives attachment to the coastal

cartilages

of the ribs as well as providing a bony

origin for the pectoral muscles

the sternum is consists of eight

individual bones called sterne bray that

tend to fuse as age advances

manubrium is the first segment of the

sternum

it is longer than the other sternobray

the body is the middle portion composed

of several sterner brain

and finally the siphoid process is the

last segment of the sternum

it is wide and flat and it holds the

siphoid cartilage

that ends our lecture on the remaining

parts of the actual skeleton

i hope you are now able to differentiate

vertebrae from one another

familiar with the vertebral formula of

dog the number of rib pairs

and segments of the sternum a short quiz

on this part module is prepared for you

to answer

after that you may now proceed to part 4

of module 2

which is the bones of the thoracic limb