Comparative anatomy( Chordates)

Skeletal system

1-Human 2-Ruminant 3-Avian 4-Horse 5-Fish Dr.Omer

Comparative Anatomyinvolves comparing the body structures of

species is the study of differences and similarities

in the anatomy of different species . It is closely related to evolutionary biology

and phylogeny .

ConceptsPhylogeny: (inheritance)  the history of

the evolution of a species or group, especially in reference to lines of descent and relationships among broad groups of organisms

Evolution: (modification and inheritance) evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection

Convergence: found in distantly related groups; evolved independently.

Parallelism: found in closely related groups; evolved independently.

Comparative anatomy Includes:• Change, adaptation, and mutation of species

• The invasion of new territories

• Species compatibility with surroundings

How can comparative anatomy help us?

1-Understand our history 2- Show how organisms function 3-Consider plans for change 4-How they develop

5-Improve animal genetics6-Preserve endangered species

Why should we be aware of comparative anatomy?

Variations in care for animals

Differences in animal habits

Structural development

Homologous Structures

Analogous Structures

Homologous structures

Are structures that are similar in two organisms because they have a common ancestor Organs with similar structure but different functions are called Homologous structures

Bones in the forelimb of the human, whale, cat, bat, bird are used for vastly different movement, they all have remarkably similar structure and organization (bones, nerves, blood vessels)

This indicated common ancestry (DNA)

Homologous Structures (BONES in the FORELIMBS) Homologous Structures (BONES in the FORELIMBS)

Analogous structures

• Features of different species that are similar in function but are structurally different

• Do not have a common ancestry• Evolved due to a similar environmental challenge• Ex) Birds & insects have wings to fly although their

wing structure is different• Analogous structures are caused by convergent

evolution. In convergent evolution, two species evolve the same traits to adapt to an environment side by side, but they didn't come from the same ancestor

Analogous StructuresE.g. Bird wing and

insect wing

Embryology

• Humans have pouches in early development• In fish these pouches develop into gill slits• In humans they form the eustachian tube and auditory

canal.• Human embryo has a tail and body hair like embryos

of all other mammals but in the human embryo these features disappear before birth

Vertebrate Vertebrate embryos are embryos are structurally structurally similar in early similar in early embryonic embryonic stages.stages.

Directional Terms

Used to describe the positions of structures on the body relative to other structures or locations

DIRECTIONAL TERMSDIRECTIONAL TERMS Definition of terms:

Anterior (cranial) toward the headPosterior (caudal) toward the tailCranial head regionCaudal pertaining to the tail regionDorsal toward the back (top) of the

animalVentral toward the belly of the animalMedial toward the median lineDistal away from the center or originProximal toward the center or origin

Caudal Cranial

Dorsal

Ventral

REGIONAL NAMESThese names are given to specific regions of the body for reference.Examples: Cranial (skull), Thoracic (chest), Brachial (arm), Patellar (knee), Cephalic (head), Gluteal (buttock)

Body CavitiesVentral body cavity

Contains most of the soft organs; divided by thin diaphragm Thoracic cavity- heart, lung, esophagus, blood

vessels Abdominal cavity- digestive tract Pelvic cavity- urinary organs, reproductive organs

Dorsal body cavityContains the brain and spinal cord

Cranial cavity- brain Spinal cavity- spinal cord

Spinal Cavity

Dorsal Cavity

Ventral Cavity

Abdominal Cavity

Diaphragm

Thoracic Cavity

Cranial Cavity

Chordates All chordates have the following features at some

stage in their life (in the case of humans and many other vertebrates, these features may only be present in the embryo):

NotochordDorsal Hollow Nerve Cord Pharyngeal slits  Post-anal tail  

Characteristics of the ChordatesNotochord, dorsal hollow nerve cord, pharyngeal gill

slits, blocks of muscle, postanal tail

Pharyngeal SlitsPharyngeal slits are openings in the pharynx (the region just

posterior to the mouth) that extend to the outside environment

. In organisms that live in aquatic environments, pharyngeal slits allow for the exit of water that enters the mouth during feeding. Some invertebrate chordates use the pharyngeal slits to filter food out of the water that enters the mouth.

In vertebrate fishes, the pharyngeal slits develop into gill arches, the bony or cartilaginous gill supports.

In most terrestrial animals, including mammals and birds, pharyngeal slits are present only during embryonic development. In these animals, the pharyngeal slits develop into the jaw and inner ear bones.

Post-anal Tail

The post-anal tail is a posterior elongation of the body, extending beyond the anus.

The tail contains skeletal elements and muscles, which provide a source of locomotion in aquatic species.

In some terrestrial vertebrates, the tail also helps with balance, courting, and signaling when danger is near.

In humans and other apes, the post-anal tail is present during embryonic development, but is vestigial as an adult

Blocks of Muscle - Myotomes • Surrounding the notochord and nerve cord are blocks of muscle - myotomes

Higher Classification of ChordataPhylum Chordata

Subphylum Urochordata – tunicates, sea squirts

Subphylum Cephalachordata – lancelets

Subphlum Vertebrata- vertebrates

Vertebrate Higher ClassificationSuperclass Agnatha - without jawsClass Myxini – hagfishesClass Cephalaspidomorphi – lampreys

Superclass Gnathostomata – with jawsClass Chondrichthyes – sharks, rays,

chimaeras(Cartilaginous fishes)Class Actinopterygii – ray-finned fishesClass Sarcopterygii – lobe-fin fishesClass Amphibia – frogs, salamandersClass Reptilia – snakes, lizards, crocodilesClass Aves - birdsClass Mammalia - mammals

skeletal system The skeletal system consists of the bones and

joints along with the cartilage and ligaments that occur at the joints.

Bones: Hard Tissue, mostly calcium phosphate and calcium carbonate, provides support and makes Red Blood Cells

Ligaments: Strong, white bands of tissue that connect two bones together at a joint

skeletal systemCartilage: Hard tissue that prevents bones from

grinding against each other. Joints: Location of where two or more bones meet.Tendon: Connects muscle to bone.

Skeletal System - FunctionsProvides the frame and support for all the

other systems and organsAids in movementProvides protectionSite of mineral storageSite of blood cell formationMade up of bones,

cartilage, and connective tissue

Two types of skeleton

Exoskeleton (protective structure on the outside of the body)

Endoskeleton (protective structure on the inside of the body)

Endoskeleton

Exoskeleton

Types of Bone Long bones: longer than they are wide; shaft

& 2 ends (e.g.: bones of arms & legs,except wrist, ankle & patella)

Short bones: roughly cube-shaped (e.g.: ankle & wrist bones)

Sesamoid bones: short bones within tendons (e.g.: patella)

Flat bones: thin, flat & often curved (e.g.,: sternum, scapulae, ribs & most skullbones)

Irregular bones: odd shapes; don't fit into other classes (e.g.: hip bones & vertebrae)

Classification of Bones on the Basis of ShapeClassification of Bones on the Basis of Shape

Cartilage – Characteristics

Mostly water; no blood Mostly water; no blood vessels or nervesvessels or nerves

Tough, resilientTough, resilientNew cartilage forms from New cartilage forms from chondroblastschondroblasts

Heal poorlyHeal poorly

Types of Cartilage

Hyaline Cartilages: fine collagen fiber matrix- most abundant type- found in articular (movable joint) cartilages, costal cartilages (connect ribs to sternum), respiratory cartilages (in larynx & upper respiratory passageways) & nasal cartilages

Elastic Cartilages: similar to hyaline cartilage, more elastic fibers (very flexible) – found in external ear & epiglottis (larynx covering)

Fibrocartilage: rows of chondrocytes with thick collagen fibers; highly compressible with great tensile strength- found in menisci of knee, intervertebral discs & pubic symphysis

Types of Joint There are 4 types of joints :

HingeKnee

Ball and SocketHip

GlidingVertebrae

Fixed ( Cartliaginous)Skull

Hinge joint

Human Skeleton

206 Bones206 BonesAxial skeletonAxial skeleton: (80 : (80

bones) in skull, bones) in skull, vertebrae, ribs, vertebrae, ribs, sternum, hyoid bone sternum, hyoid bone

Appendicular Appendicular SkeletonSkeleton: (126 bones)- : (126 bones)- upper & lower upper & lower extremities plus two extremities plus two girdles girdles

Half of bones in hands Half of bones in hands & feet & feet

Skull

Sternum

Ribs

Vertebral column

Metatarsals

Metacarpals

Phalanges

ClavicleScapula

Humerus

RadiusPelvisUlnaCarpals

Femur

Patella

FibulaTibiaTarsals

Phalanges

The Skeletal System Section 36-1

Axial Skeleton

Appendicular Skeleton

Axial skeleton

Appendicular skeleton

7 Cervical Vertebras

13 Thoracic Vertebras

6 Lumbar Vertebras

5 Sacral Vertebars

18-20 Coccygial vertebras

Pneumatic bonesThe pneumatic bones are important to the

chicken for respiration.They are hollow bones connected to the chicken’s respiratory

system and are important for the chicken Examples of pneumatic bones:

skull, humerus, clavicle, keel(sternum)pelvic girdlelumbar and sacral vertebrae.

Medullary bonesThe medullary bones are an important source of

calcium for the laying hen.

Calcium is the primary component of egg shells and a hen Mobilizes 47% of her body calcium to make an egg

shell.

Examples:tibia, femur, pubic bones, ribs, ulna, toes, and scapula.

Fish skeletal system The function of the skeletal system is one of

support.Skeletal tissues:

Axial skeleton:

Head, trunk, and tail regions.Head: Trunk skeleton: modified portion of the

vertebral column.Tail skeleton: remainder of the vertebral

column

Fin :To allow the fish to stay upright, move, and maneuver in the water.

Rays : soft cartilage structure that supports the fins of the fish.Tail Fin : Helps to propel the fishDorsal and Anal Fins : balance and close quarters movements.Pectoral Fin : allows to fish to dive and also allows the fish to stay in one spot.Pelvic Fin : balances and positions .Lateral Line : helps the fish detect vibration, sensors, and helps the fish to find food and to navigate to avoid predators.

Cattle Sheep Horse Humans Poultry

Cervical 7 7 7 7 14

Thoracic 13 13-14 18 12

Lumbar 6 6-7 6 5

Sacral 5 4 5 (fused)

5 (fused)

Coccygeal 18-20 16-18 4 (fused)

6

Number of Vertebrae in Selected Animal Species

Bird

66