Lab 6 Chordata and Vertebrate Tissues

Phylum Chordata main characteristics (5):

• bilateral symmetry

• coelomates

• deuterostomes

• segmentation

• joint appendages

All animals in Phylum Chordata have these 4 features:

• Dorsal hollow nerve cord: becomes CNS in vertebrates

• Notochord (cartilaginous rod): provides support; becomes a vertebral column in vertebrates

• Pharyngeal slits: openings in the pharynx that develop into gills or parts of the ear or throat

• Post-anal tail: used in locomotion (or lost in some species)

Subphylum Urochordata

Tunicates and Sea Squirts

Subphylum Urochordata life cycle

• Motile Larval Stage (looks like a tadpole)

  • possesses the notochord and nerve cord, the post-anal tail, and the pharynx with slits

• Sessile Adult Stage:

  • the tail, notochord, and nerve cord are all lost, and the body becomes basically a large pharynx. the slits are used to filter water for food particles

Subphylum Cephalochordata

Lancets (Amphioxus): Small, fish-like marine chordates

Subphylum Cephalochordata characteristics

• they burrow in the sand or mud (found in shallow seas)

• they filter feed

Subphylum Vertebrata

Vertebrates (includes humans)

• fish, sharks, amphibians, reptiles, birds, and mammals

Subphylum Vertebrata characteristics

• have a jointed, dorsal vertebral column (a backbone) that replaces the notochord in embryonic development

• have an anterior skull with a brain

• have internal organs suspended in a coelom

• have a well-developed circulatory system driven by contractions of a ventral heart

Class Agnatha/Cephalaspidomophi (of Subphylum Vertebrata)

Jawless fish: Lampreys and hagfish

Class Agnatha/Cephalaspidomophi characteristics

• Lampreys and hagfish use their sharp sucking mouth to parasitize larger animals, like fish

• reproduce in freshwater streams but parasitize fish in oceans

Class Chondrichthyes (of Subphylum Vertebrata)

Cartilaginous Fish: sharks, skates, rays, and chimaeras (spotted ratfish)

Class Chondrichthyes characteristics

• the first vertebrates to evolve jaws, and they arose from specialized pharyngeal arches

  • this allowed improved feeding efficiency, the ability to grasp, subdue, swallow large prey

• like Cephalaspidomophi, they have a cartilaginous endoskeleton, but also developed a jaw

• the jaws seen in modern fish and sharks support more teeth and more dexterity, which in turn aids in digestion

• most are marine predators

• have paired fins

• rely on oil-rich livers for buoyancy

• the skeleton is composed of hard, pliable cartilage, and the skin is flexible and leathery

• rays and skates have flattened bodies for life on the sea floor

  

Class Osteichthyes/Actinopterygii (of Subphylum Vertebrata)

bony fish (the skeleton is hardened with calcium)

Class Osteichthyes/Actinopterygii characteristics

• more flexible fins than cartilaginous fishes

• most have a swim bladder for buoyancy (allows the fish to control the depth at which it remains suspended in the water while expending very little energy to maintain its position)

• outer body surface is covered with flat, thin scales

• gills open into a chamber covered with a hardened flap called the operculum (movement of the operculum improves the flow of water over the gills)

• most fish have a pair of pectoral fins behind gills and pair of pelvic fins anterior to anal region

• all vertebrates from this point forward have a calcium hardened skeleton

Lobe-finned fishes (of Subphylum Vertebrata)

• the first vertebrates to colonize land were likely the lobe-finned fishes

• they live in stagnant swamps and muddy waters

• they have muscular fins supported by bones that are similar to the bones of amphibians, like frogs and toads

Class Amphibia (of Subphylum Vertebrata)

Frogs, Toads, Salamanders, and Caecilians

Class Amphibia characteristics

• all terrestrial vertebrates are tetrapods (animals with four limbs)

• Amphibians were the first tetrapods to evolve

• most amphibians are confined to moist environments (because they lose water rapidly through their skin)

• their eggs are fertilized externally

• Terrestrial adaptations:

  • lungs (but also cutaneous resp.)

  • mucous coating skin

  • inner ear (to better hear in the air) - like the jaw, the inner ear bones derive from pharyngeal arches

Class Reptilia (of Subphylum Vertebrata)

Crocodiles, Alligators, Turtles, Snakes, and Lizards

Class Reptilia characteristics

• reptiles were able to fully colonize land with the evolution of the amniotic egg (a fluid-filled egg with a shell that protects and nourishes a developing embryo)

  • leathery shell prevents desiccation

  • stores food – yolk sac

  • gave rise to internal gestation in mammals

• other terrestrial adaptations in reptiles:

  • leathery skin

  • scales/wings and feathers

  • more advanced lungs

  • better adapted limbs – locomotion

  • better adapted vision and hearing

(Reptiles and mammals are the amniote taxa that share this derived trait, although the Mammalian egg lost its shell and yolk so embryo receives nutrition directly from the mother)

Class Aves (of Subphylum Vertebrata)

birds

Class Aves characteristics

• only animals with feathers (alongside dinosaurs)

• they are homeotherms (maintain a constant body temperature - warm-bloodedness)

• highly adapted vision and lightweight skeleton for flight

Class Mammalia (of Subphylum Vertebrata)

mammals

Class Mammalia characteristics

• Incubate young internally (in their shell-less eggs) in the uterus (except Monotremes, which are the only mammals that lay actual eggs)

• have special glands on the skin called sweat glands, and even more specialized versions of sweat glands called mammary glands (which produce milk to feed newly born offspring)

• have hair

• have homeothermy (maintain a constant body temperature - warm-bloodedness)

• relatively larger brains

Embryo difference between class reptilia and class mammalia

Vertebrate Animal Tissue

• Tissues: cells with similar structure/function

• Organ: several tissues that work together to perform a common function

• Organ system: more than one organ unified by a common purpose.

  • organ systems make up an organism

Histology

the study of microscopic morphology (structure)

There are 4 traditional tissue types:

• Epithelial tissue

• Connective tissue

• Muscular tissue

• Neural tissue

Epithelial Tissue (what it is and function)

A cellular sheet that covers or lines structures

(ex: the outside of the body, internal organs, GI tract, vessels, and secretory glands)

• Function:

  • protection

  • selective barrier

  • impermeable barrier

  • secretion

  • sensory surface

• Basement membrane is a protein layer epithelial cells sit on

Epithelial Tissue (its layers)

Layers:

• Simple = one layer

• Stratified = multiple layers

• Pseudostratified = appears multiple

Shape:

• Squamous = flat/fried egg (nucleus = yolk)

• Cuboidal = square

• Columnar = tall columns/rectangles

Simple squamous

blood vessel lining, lung alveoli

Stratified squamous

epidermis, esophagus lining

Simple cuboidal

kidney tubules, liver

Simple columnar

Stomach & intestinal lining

Pseudostratified ciliated columnar epithelium

ciliated airways of the lung

• All the cells rest on the basement membrane, but not all reach the surface

Connective Tissue functions

• Supportive tissue with a characterizing extracellular matrix

• Store energy (adipose)

• Connect structures (tendon/ligaments)

• Support (dermis of skin, bone)

• Protection (immunity- white blood cells)

• Transportation (blood)

Loose connective tissue

scattered amorphous ground substance with fibers that are “loosely” connected

• Collagen: found in skin

• Elastin: Elastic structures like those making your nose

• Reticulin: supporting mesh in soft tissues such as  in liver and bone marrow

Dense connective tissue

tightly packed collagen fibers

• tendons and ligaments

Fibroplasts

Loose and dense connective tissue consist of cells called fibroblasts that make connective tissue fibers

Specialized Connective tissue

• Blood

• Cartilage

• Bone

• Fat

Adipose

fat - a type of loose connective tissue

Reticular tissue

spleen, lymph node - a type of loose connective tissue

Hyaline cartilage

joint surfaces - a type of dense connective tissue

Elastic cartilage

ears, nose - a type of dense connective tissue

Plasma

The fluid extracellular matrix that surrounds red blood cells, platelets, etc.

Platelets

cell fragments used in clotting

Erythrocytes

Red blood cells

• filled with hemoglobin → O₂ and CO₂

• No nuclei

Leukocytes (and their 2 types)

white blood cells

• Granulocytes

• Agranulocytes

Granulocytes

have visible protein granules in their cytoplasm

• Three types

  • Neutrophils: neutral staining, most numerous

  • Eosinophils: acid staining, kill nematodes

  • Basophils: basic staining, turn into mast cells involved in inflammation

Agranulocytes

lack granules

• Two types:

  • Monocytes in blood = macrophages (a type of white blood cell that surrounds and kills microorganisms, removes dead cells, etc.) in tissue (orchestrate immunity)

  • Lymphocytes make antibodies, help macrophages, kill specific target cells

Chondrocyte

cartilage cells

Osteocyte

bone cells

Lacunae (little lake)

hollow fluid-filled spaces that Cartilage and bone cells live in

Osteon

columnar unit of bone

consists of:

• Haversian canal: blood vessel-filled chamber: gas exchange with osteocytes

• Lacunae: chambers containing the osteocytes

• Canaliculi (little canals): connect the lacunae

Muscle

a type of contractile tissue

Sarcomeres

the contractile units of muscle

• contains overlapping thin filaments (actin) and thick filaments (myosin)

Striated muscle

Row of sarcomeres

• Two types:

  • skeletal muscle

  • cardial muscle

Skeletal muscle

• a type of striated muscle

• attached to bone by ligaments

• multinucleated (syncytial theory)

• locomotion

Cardial muscle

• a type of striated muscle

• Intercalated disks: gap junctions and desmosomes

  • Connect cardiac muscle cells

  • Electrical coupling for synchronized beats and mechanical strength

• Only branched muscle cells – network structure increases mechanical strength

• Fewer nuclei than skeletal muscle

Smooth muscle

No sarcomeres; not striated. Still contracts - peristalsis

• found in the GI tract, uterus, and blood vessels

• controlled by autonomic nervous system

• there is a lining of arteries and lesser extent in veins

Neural tissue

Neurons are comprised of:

• Dendrites - receive stimuli and are extensions of the cell body

• Axons - transmit action potentials

• Terminals - release neurotransmitters

• Schwann cells - glial cells that wrap around the axon making action potentials travel faster - myelin

Glial cells

• found in neural tissues

• are supportive cells

• Produce myelin and CSF, maintain blood brain barrier, act as immune cells, etc

• Outnumber neurons 10 to 1