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Comparative Anatomy And Physiology Of Animals > Skeletons > Flashcards

Skeletons Flashcards

1
Q

What is a skeleton

A

Any structure that:
Maintains body shape
Supports and protects a body
Transmits contractile forces

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2
Q

3 types of skeletons

A

Hydrostatic skeletons
Exoskeleton
Endoskeleton

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3
Q

Hydrostatic skeleton

A

Associated with the presence of a fluid-filled body cavity

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4
Q

Body cavity

A

Distinguished by presence of coelom (body cavity)
Coelom is filled with coelomic fluid - separates intestines and organs
- fluid absorbs shock and acts as hydrostatic Skelton
Coelom is lined with peritoneum

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5
Q

Pseudocoelomate

A

Coelom lost and replaced with pseudocoelom (persistent blastocoel).
Unlined cavity.

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6
Q

What type of skeleton is the ancestral condition for most coelomate bilaterians

A

Hydrostatic skeleton

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7
Q

Characteristics of hydrostatic skeletons

A

Fluid (water-filled) skeleton
Supported by fluid pressure
Hydrostatic have constant volume—> transmits muscle contractile forces
Cylindrical bodies
Polyps and vermiform (worm-like) animals

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8
Q

Support structure of hydrostatic skeleton

A

Body walls reinforced with a mesh of inelastic fibres
-orthogonal pattern = doesn’t allow for changes in length, bends until failure from kinking , allows for torsion
-cross-helical pattern = allows for changes in length, bends in a curve and resists torsion

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9
Q

Most common pattern of support structures in hydrostatic skeleton mesh

A

Cross-helical pattern

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10
Q

Muscle structure and movement in hydrostatic skeleton

A

Longitudinal muscles
Circular muscles

Muscles can only contract (not push)
Localised muscle contraction displaces fluid to another part of the body (where muscles are relaxed)

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11
Q

Movement using a hydrostatic skeleton

A

Circular muscle at posterior end contracts.
Forces fluid forwards and extends the front of the animal.
Longitudinal muscles contract to pull posterior end forwards

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12
Q

Segmentation in hydrostatic skeleton

A

In annelids (e.g., earthworm), the coelom is divided into segments by muscular septa.
Prevents movement of fluid from one segment to another.
Allows individual segments to operate independently.
More complex and variable pattern of movement.
Protection from injuries.

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13
Q

Molluscan exoskeleton

A

Form of a calcareous shell protecting a soft-bodied animal with a hydrostatic skeleton

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14
Q

What secretes the calcareous shell in molluscs

A

Mantle epithelium
Secreted into extrapallial space
Protected by periostracum

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15
Q

Calcareous shell- 3 layers

A

Periostracum (P)
-Outermost ‘leathery’ organic layer
-Made of the protein conchiolin
Prismatic layer (PL)
-CaCO3
Nacreous layer (NL)
-CaCO3
-Pearly

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16
Q

Prismatic layer of molluscs shell

A

The middle & thickest layer of the shell is the prismatic layer
Secreted at the mantle edge (the periostracum acts as a framework on which the calcium carbonate is suspended)

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17
Q

Nacreous layer of molluscs shell

A

Inner layer of the shell
In some species looks like mother of pearl
Forms from thin sheets of calcium carbonate alternating with organic matter (eg keratin, collagen, chitin)
Cells over the entire epithelial layer of the mantle secrete the nacreous layer. This thickens the shell
Doesn’t limit growth of the animal

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18
Q

Growth rings in mollusc shells

A

When conditions are harsh the mantle may stop secreting the shell.
When conditions improve, the mantle starts again
These can be seen as growth rings

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19
Q

Biomineralisation pathway

A

Calcium carbonate (CaCO3) is formed from calcium and bicarbonate ion (HCO3-), the derivative of carbonic acid, contained in sea water. The Calcium ions in sea water are funnelled through into the extrapallial space through intercellular diffusion (1), active transport via calcium ATPase ion pumps (2), and calcium channels (3). The extrapallial space is then the calcification site.

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20
Q

Arthropod exoskeleton

A

Composed of a thick hard cuticle

Protects internal tissues from dehydration & infection and offers support for the internal organs.
It also provides sites for muscle attachment allowing movement.

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21
Q

Structure of arthropod exoskeleton

A

The cuticle is secreted from the epidermis of the body wall
The cuticle is essentially layers of protein + a waterproof polysaccharide called chitin
In crustaceans (crabs, lobsters etc.) the exoskeleton contains calcium carbonate crystals – making it very inflexible

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22
Q

Layers of arthropod exoskeleton

A

The epicuticle is the hardened outer layer – made of waxy lipoprotein - it is waterproof and acts as a barrier to microorganisms.
The procuticle (the combined exocuticle and endocuticle) is largely chitin & proteins.
The procuticle hardens through a process of sclerotization (tanning – protein layers are cross-bonded to one another).

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23
Q

Sclerotization

A

Protein layers are cross-bonded to one another

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24
Q

Arthropod joints

A

Invaginations of exoskeleton result in ridges for muscle attachment
At the joints the procuticle is thinner and less hardened
This is called the articular membrane

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25
Q

Growth and exoskeletons

A

Moulting or ecdysis

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26
Q

Ecdysis

A

Epidermal glands secrete enzymes that begin to digest the procuticle
This separates the epidermis and the procuticle.

New procuticle and epicuticle are secreted
Old exoskeleton splits along ecdysal lines when the animal expands by air or water intake
Pores in the procuticle secrete additional epicuticle
Calcium carbonate (crustaceans) or sclerotization hardens exoskeleton

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27
Q

Echinoderm endoskeletons

A

Echinoderms have endoskeletons formed by skeletal ossicles located within the dermis and covered with epidermis.
Skeletal ossicles provide rigidity and muscle attachment sites.
The connective tissues surrounding the skeletal ossicles also play a key skeletal role.

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28
Q

Echinoderm body wall

A

Consists of:
Thin cuticle
Monolayered epidermis
Thick connective-tissue dermis (houses skeletal ossicles)
Coelomic epithelium of myoepithelial cells
Peritoneum

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29
Q

Components of echinoderm endoskeleton

A

the calcareous ossicles and the collagenous connective tissues.
Skeletal ossicles provide rigidity and muscle attachment sites.

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30
Q

Echinoderm connective tissue

A

The connective tissues surrounding the skeletal ossicles also play a key skeletal role.
Collagenous ligaments suture ossicles together to create the skeletal framework.
Echinoderms can reversibly vary the rigidity of their dermis and general connective tissue.

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31
Q

Skeletal ossicles

A

Skeletal ossicles form intracellularly in a syncytium of fused dermal sclerocytes
Ossicles consist of a 3D lattice called a stereom, with the spaces within called the stroma.
Honeycomb structure reduces weight, increases strength and prevent cracking.

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32
Q

Spines

A

All ossicles, including those that project above the body surface, are endoskeletons and are covered by epidermis.

33
Q

Types of skeletal supporting structures

A

Cartilage
Bone

34
Q

Cartilage

A

Hard and pliant material
Chondroitin suplhates (polysaccharides) which bind with ground substance proteins to form proteoglycans
Chondrocytes produce a large amount of extracellular chondroitin sulphate matrix interspersed with collagen out or elastic protein fibres

35
Q

3 types of cartilage

A

Hyaline cartilage
Fibrocartilage
Elastic cartilage

36
Q

What is appearance and functional role of cartilage dependent on

A

Number and type of protein fibres

37
Q

Where is hyaline cartilage formed

A

Embryonic bones
Nose
Tips of ribs
Tracheal rings
Articular ends of long bones

38
Q

Hyaline cartilage

A

Most common type of cartilage in the body.
Consists of short and dispersed collagen fibres and contains large amounts of proteoglycans.
No fibres are visible when viewed under light microscopy.
A plate of hyaline cartilage at the ends of bone allows continued growth until adulthood.

39
Q

Where is fibrocartilage found

A

Intervertebral disks
Pubic symphysis

40
Q

Fibrocartilage

A

Collagen fibres are abundant giving mechanical resistance to tensile forces
Found under conditions where tensile or warping loads applied

41
Q

Where is elastic cartilage found

A

Internal support for ear
Epiglottis

42
Q

Elastic cartilage

A

Predominate protein fibre is elastin, which makes the cartilage springy and flexible.
Elastic cartilage gives rigid support as well as elasticity.

43
Q

Bone structure

A

has a soft framework made of the protein collagen, impregnated with calcium phosphate, which adds strength and hardens the framework.
This combination of collagen and calcium makes bone strong but flexible enough to withstand stress.

44
Q

Types of bone cells

A

Osteoblasts – osteogenesis (producing new bone)
Osteoclasts – remove existing bone
Osteocytes – maintain equilibrium in fully formed bone

45
Q

Osteoblasts

A

the bone cells responsible for producing new bone, or osteogenesis. Osteoblasts synthesise and secrete the collagen matrix and calcium salts

46
Q

Osteoclasts

A

responsible for removing existing bone. Osteoclasts are multinucleated and originate from white blood cells instead of from osteogenic stem cells. Osteoclasts are continually breaking down old bone while osteoblasts are constantly forming new bone.

47
Q

Osteocytes

A

formed from osteoblasts that get trapped within the calcified matrix that they secreted.
Osteocytes are the primary cell of mature bone and the most common type of bone cell.
Osteocytes maintain the mineral concentration of the matrix via secretion of enzymes.

48
Q

Osteon

A

Series of concentric rings of bone cells and layers of bone matrix around a central canal that houses blood vessels, lymph vessels and nerves

49
Q

2 types of bone

A

Compact bone
Spongy/cancellous bone

50
Q

Compact bone

A

Dense
Formed of osteons

51
Q

Spongy/cancellous bone

A

Osteocytes housed in lacunae inside trabeculae - maximise strength at areas of stress, with each trabecula forming along lines of stress
The spaces of the trabeculae network provide balance to the dense and heavy compact bone by making bone lighter. Marrow occupies the cavities and is lined with endosteum. Marrow also contains connective tissue fibres, blood vessels, nerve fibres and adipose tissue. Hemopoietic tissue (red marrow) produces red blood cells and some white blood cells.

52
Q

2 parts of a long bone

A

Diaphysis
Epiphysis

53
Q

Diaphysis

A

Tubular shaft
Medullary cavity- hollow region filled with yellow marrow
Composed of compact bone matrix around

54
Q

Epiphysis

A

Wider section at each end of the bone
Filled with spongy bone

55
Q

Metaphysis

A

Where the epiphysis and diaphysis meet
Contains the epiphyseal plate - a layer of hyaline cartilage in growing bone

56
Q

2 types of bone development

A

Endochondral
Intramembranous

57
Q

Endochondral ossification

A

Mesenchymal cells differentiate to chondrocytes that form the cartilaginous skeletal precursors of bone.
Hyaline cartilage is surrounded by perichondrium.
Hyaline cartilage in core of diaphysis ossified by accumulation of inorganic salts. Entombed chondrocytes die and blood vessels invade and erode calcified cartilage to form initial spaces of marrow
Osteoblasts appear in the core of the bone and primary centre of ossification appears. Old cartilage replaced by bone. Trabeculae form. Cartilage replacement moves to the metaphysis.
Epiphyseal plate is last region of cartilage proliferation.
Fishes, amphibians and reptiles have indeterminate growth – they can continue to grow through life.
Birds & mammals have determinate growth and stop growing at maturity

Mammals, some lizards and birds secondary centres of ossification arise in the epiphysis.
At sexual maturity in mammals the epiphyses ossify completely. Cartilage remains at joint surface as articular cartilage

58
Q

Intramembranous ossification

A

Direct development from mesenchyme tissue without cartilage precursor
Dermal bone – skull, pectoral girdle and integument
Sesamoid bone – associated with tendons
Perichondral bone – develops early and retain ability to form bone in the adult

Mesenchymal cells group into clusters and ossification centres form.
Secreted osteoid traps osteoblasts, which then become osteocytes.
Trabecular matrix and periosteum form.
Compact bone develops superficial to the trabecular bone and crowded blood vessels condense into red marrow.

59
Q

Types of vertebrate skeletons

A

Cartilaginous
Bony

60
Q

Osteichthyes

A

Have bony endoskeletons
Formed through Endochondral ossification
Bone replaces cartilage

61
Q

Basal vertebrates

A

Cartilaginous endoskeletons
Could show some level of mineralisation

Cartilage calcification
-Accumulation of calcium salt in cartilage
Perichondral ossification
-Bone forms on cartilage surface

62
Q

Placoderms

A

have cartilaginous endoskeletons with ossification perichondral ossification
Head and torso covered in extensive bony armour plates.
First vertebrates to have paired pelvic fins.

63
Q

Ossification in chondrichthyans

A

Endoskeleton of prismatic calcified cartilage
Cartilaginous skull
Bone present in scales (dermal denticles) and teeth
Some sharks show perichondral ossification along vertebrae

64
Q

Basic Bauplan of vertebrate skeletons

A

Splanchnocranium
-Primary palate and jaws, branchial elements
Neurocranium
-Braincase
Axial skeleton
-Backbone and ribs
Appendicular skeleton
-Pectoral and pelvic fins or limbs and girdles
Dermal skeleton
-External portions of the skull, teeth, armour plates, clavicle, patella

65
Q

Developmental origins- endoderm

A

Splanchnocranium

66
Q

Developmental origins- mesoderm

A

Splanchnocranium
Neurocranium
Axial skeleton
Appendicular skeleton

67
Q

Developmental origins - ectoderm

A

Splanchnocranium
Dermal skeleton

68
Q

Splanchnocranium

A

Primary palate and jaws, branchial elements

69
Q

Neurocranium

A

Braincase

70
Q

Axial skeleton

A

Backbone and ribs

71
Q

Appendicular skeleton

A

Pectoral and pelvic fins or limbs and girdles

72
Q

Dermal skeleton

A

External portions of the skull, teeth, armour plates, clavicle, patella

73
Q

Evolution of the exoskeleton

A

Bony exoskeletons are widespread across both cartilaginous and bony vertebrates, first appearing in Galeaspida.
Exoskeletons form through cartilage calcification, intramembranous ossification or perichondral ossification

74
Q

Evolution of ossification

A

In stem vertebrates, endoskeleton composed entirely of cartilage.
Osteostracans and non-osteichthyes jawed vertebrates evolved ossified endoskeletons. Endo- and exoskeletons developed on the surface of cartilage (perichondral ossification).
Osteichthyes acquired endochondral ossification
Bony tissues are produced within (as well as on top of) cartilage.
Bony tissues eventually replace cartilage.

75
Q

Tetrapod Bauplan

A

Cranial skeleton
-Skull and mandible

Axial skeleton
-Cervical skeleton
-Thoracic skeleton
-Caudal skeleton

Appendicular skeleton
-Limbs and girdles

76
Q

Hagfish skeleton

A

only have cartilaginous skulls (chondocranium) and no vertebral column around notochord
But have arcualia (cartilaginous precursors to vertebrae) in the tail.

77
Q

Lamprey skeleton

A

have an internal skeleton consisting of:
A notochord
Vertebra-like structures
An attached cartilaginous skull and gill arches
Fin rays

78
Q

Basal vertebrates

A

only possessed cartilage
Lack mineralised skeletons
Calcified cartilage in galeaspids but no bones

Living examples:
Cyclostomes (Hagfish & lampreys)

Extinct examples:
Conodonts
Galeaspids

79
Q

Perichondral ossification

A

Bone formation on outside of cartilage

Comparative Anatomy And Physiology Of Animals (9 decks)

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