UCSC Comparative Vertebrate Anatomy Midterm (3)

notochord

A flexible (side-to-side) incompressible rod that flexes, supports, and stabilizes the body

A long, continuous rod of fibrous connective tissue wrapping a core of fluid or fluid-filled cells

vertebral column

Discrete serially repeating segments of cartilage or bone

A discrete, but repeating series of cartilaginous or bony elements

Haikouella/Haikouichthys

Cephalochordates that gave rise to cyclostomes

Describe the notochord of cyclostomes.

Hagfish --> notochord only
Lamprey --> notochord with cartilage segments attached

Function of neural spines/arches

To protect the dorsal hollow nerve cord

Function of hemal spines/arches

To protect the aorta or blood vessels

intercentrum/pleurocentrum

Bases of ventral arches that support the arches

centrum

The body of a single vertebrae

What are the 3 general trends in evolving vertebrae?

1. Enlargement of some elements
2. Displacement of notochord
3. Regional variation --> cervical, thoracic, lumbar, sacral, and caudal (or in fish --> precaudal and caudal)

What are the reason to evolve a vertebral column?

1. Protect dorsal hollow nerve cord, dorsal aorta, and blood vessels
2. Support body; locomotion --> suspends body
3. Muscle attachment sites

nucleus pulposus

The soft, fibrocartilaginous, central portion of intervertebral disk only found in mammals

What do other vertebrates besides mammals have instead of nucleus pulposus?

Intervertebral discs or intervertebral cartilages --> any "padding" between centra

What are some ways we find diversity in the axial skeleton?

1. Vertebral types
2. Vertebral articulations
3. Rib connections and sternum
4. Axial column (shape --> locomotion) --> stability
5. Regionalization (cervical, thoracic, etc.)
6. Vertebral number

aspidospondyl

A vertebral type in tetrapods characterized by separate from vertebral elements ("rachitomous")

--> neural spine, neural arch, intercentrum, and pleurocentrum

holospondyl

A vertebral type in tetrapods characterized by centrum fused parts and notochord remains

What are vertebral articulations in the holospondyl condition?

Different ways that centra are connected

acoelous

A vertebral articulation in the holospodyl condition characterized by flat ends that resist compressive forces

amphicoelous

A vertebral articulation in the holospondyl condition characterized by limited side-to-side movement

procoelous

A vertebral articulation in the holospondyl condition characterized by a ball and socket for more motion in most directions and the CONVEX portion being found ANTERIORLY

opisthocoelous

A vertebral articulation in the holospondyl condition characterized by a ball and socket for more motion in most directions and the CONCAVE portion being found ANTERIORLY

heterocoelous

A vertebral articulation in the holospondyl condition characterized by saddle-shaped centra that offer food rotation BUT prevent torsional rotation (along long axis) --> found in cryptodirans and long-necked birds

neural arches

A type of dorsal arch that protects the neural tube

interneural arches

AKA intercalary --> A type of dorsal arch that protects the neural tube

hemal arches

A type of ventral arch that encloses the blood vessels

interhemal arches

A type of ventral arch that encloses the blood vessels

centra

Center of vertebrae that consists of an intercentrum and a pleurocentrum

intercentrum

One of the two basic elements of a centra

pleurocentrum

One of the two basic elements of a centra

trunk region

Anterior region of a fish

caudal region

Posterior region of a fish

cervical region

Neck region of a tetrapod

sacral region

Hip region of a tetrapod

thoracic region

Region of trunk into chest

lumbar region

Region between thorax and hips

What is the criteria for something being considered a "body"?

- Cells need to work together
- Bodies need to have a specific portion of the body that keeps the entire clump of cells alive
- Cells CAN be specialized --> i.e. heart cells, brain cells, stomach cells

Why is cell communication within bodies so important?

- Cells need to know when to die and be replaced
- Cancer is when cells don't know when to die or to stop growing
- At some point in history, cells learned to communicate, stick together, and trade proteins

What did the earliest bodies look like?

Discs and plates

What did Reginald Sprigg discover and who reinforced his discovery with further evidence?

- 1947 --> Sprigg found rocks with disc impressions
- 1960s --> Martin Glaessner proved the bodies were 15-20 million years older than originally thought --> these were some of the earliest bodies

How old were Sprigg's rocks?

600 million years old

What do hydroxyapaptite and collagen do?

- Hydroxyapatite gives bones strength when compressed
- Collagen gives bones strength when pulled

What is cartilage?

- Flexible connective tissue that is softer than bone
- Has collagen and a molecule called proteoglycan

What are placazoans?

- Discovered in the 1880s --> very simple organisms that are too simple to be "real" bodies

What was discovered about sponges in 1894?

- Sponges are even more simple than placazoans and can put themselves back together after going through a sieve

What did Nicole King study?

Microbes known as choanoflagellates

What is special about choanoflagellates?

They are microbes that have collagen and proteoglycan

What is the reason why bodies began to form in the first place?

Microbes began to band together to avoid being eaten by bigger microbes

What do you need to extract DNA from a sample?

- Plant or meat
- Salt
- Dish soap
- Meat tenderizer
- Alcohol

What differentiates nose cells from other cells?

- Every cell in the body have the DNA for all cells
- But! Only cells in nose have genes activated for smelling

How many smells can humans smell?

5000-10000 odors

On a molecular level, how does smelling work?

- Odor molecules from air enter nose and bind to tissue laden with nerve cells

What is special about fish smelling abilities?

- All vertebrates have the same general smell framework
- But fish have genes that are specialized for smelling in water

What did Linda Buck and Richard Axel discover?

- 1991 --> identified genes involved in smell

What are the 3 assumptions Buck and Axel used to identify genes involved in smell?

1. Human genes resemble mouse genes
2. Genes are only active in nasal tissue
3. LOTS of genes involved

What was the result of Buck and Axel's research?

Found all the genes involved in smell and discovered that they make up 3% of the human genome

How is smell different in more complicated organisms?

- Primitive fish such as agnathans can smell in both water and air, but only have a few genes
- Smell is more specialized in complicated organisms and have more genes due to duplications

What is special about cetaceans in terms of sense of smell?

Do not have a sense of smell anymore, but have the same number of genes as other mammals!

Describe the sense of smell of advanced primates.

Not very good, as they traded smell for sight

Describe human eyes.

- Camera-like eyes
- Light enters eye and is focused on retina
- Muscles in eye control iris, which controls how much light enters the eye
- Retina have 2 types of receptors that signal the brain
- More sensitive receptors see black and white, while less sensitive see color
- Vision cells make up 70% of all sensory cells in humans

What are the light-gathering molecules?

- Vitamin A and opsin (protein) send impulse to brain
- Animals need 3 opsin to see color and 1 opsin to see black and white
- All animals that can see use the same kind of opsin

How long ago did color vision arise?

- 55 mya --> same time as forest plants diversified
- Allowed primates to differentiate between different fruits

What did Detlev Arendt discover?

- Studied polychaete eyes (have a true eye and eyespots)
- Discovered polychaetes had normal invertebrate eyes, but had opsins usually found in vertebrate eyes
- Polychaete eyes even had bristles like vertebrate eyes

What did Mildred Hoge discover?

- Studied flies with a mutation that gave them no eyes
- Found similar mutations in mice and humans
- 1990s --> discovered these were caused by similar DNA
- Gene was named "eyeless"

What did Walter Gehring discover?

- Isolated eyeless and could insert it to form eyes all over fly bodies
- Even inserting the mouse version of eyeless worked to form eyes in flies
- Eyeless gene is now renamed Pax6 and is responsible for eye development in all mammals with eyes

apophyses

Processes on vertebrae small or large

transverse apophyses

Any process extending from the centrum of a vertebrae
- Functions vary depending on where these are along the axial skeleton

ribs

Bony struts --> fuse or articulate with vertebrae

How many heads did the ribs of primitive tetrapods have?

2

How many heads do the ribs of extant tetrapods have?

2 --> dorsal and ventral heads

diapophyses

Transverse processes that articulate with the tuberculum of the rib
- Facets that have a small concave spot for connection

parapophyses

Transverse processes that articulate with the capitulum of the rib
- Facets that have a small concave spot for connection

tuberculum

The dorsal head of a rib that connects to vertebrae

capitulum

The ventral head of a rib the connects to vertebrae

costal

Portion of rib between capitulum and sternum

sternal

Portion of rib that connects to sternum

sternum

Bone along ventral midline
- Manubrium is the upper portion
- Xiphisternum is lower portion

true rib

A rib connecting to a part of the sternum

false rib

A rib that connects to other ribs

floating rib

A rib that does not connect to anything

What is the purpose of the sternum?

- Supports ribs --> helps to build a ribcage
- Protects organs in chest cavity
- More area for muscle attachment --> we see diversity in shapes

Do fish have a sternum?

No

Did the first tetrapods have sterna?

No

Do lissamphibians have sterna?

Yes

Do turtles, snakes, and limbless lizards have sterna?

No

gastralia

Abdominal ribs
- Dermal origin (skin derived) versus the mesoderm derived true, false, and floating ribs
- Located in the belly of some fishes, lizards, crocodiles, and sphenodon
- Don't articulate with vertebrae
- Protect organs for the animals that lay their bellies on the ground
- Support hypaxial muscles
- Regionalization of axial skeleton
- Specialization of vertebrae along axial skeleton

What are the two regions of a fish body?

Precaudal and caudal

Describe precaudal vertebrae of fish.

- Have a neural spine, neural canal, and neural arch
- Have a centrum
- Have ventral, transverse ribs connected at a regions called basapophyses

Describe caudal vertebrae of fish.

Same as the typical vertebrate vertebrae

heterocercal tail

A tail fin like that of a shark, with the upper lobe longer than the lower lobe

homocercal tail

A tail with the upper and lower lobes symmetrical and the vertebral column ending near the middle of the base, as in most telost fishes

diphycercal tail

A tail that tapers to a point, as in lungfishes, vertebral column extends to tip without upturning

What gives fish stability?

- Pectoral and pelvic fins
- Allow the fish to overcome pitch, roll, and yaw

pitch

Anterior post bucking

roll

Along long axis

yaw

Side-to-side motion

What type of centra do fish have?

Procoelous/amphicoelous

What type of centra do salamanders, frogs, and crocodylians have?

Procoelous

What type of centra do lizards and snakes have?

Opisthocoelous

What type of centra do mammals have?

Acoelous

What type of centra do birds have?

Heterocoelous

What are the 5 regions of the axial skeleton?

1. Cervical (small vertebral foramen, flat)
2. Thoracic (medium vertebral foramen)
3. Lumbar (largest vertebral foramen)
4. Sacral
5. Caudal