Topic 5 - Integument, Support, & Movement

Integument

covers all external surfaces and directly continuous with mucus membranes lining internal passageways

What does the integument consist of?

skin & hypodermis

• epidermis: superficial layer; multilayered epithelium from ectoderm

• dermis: deepest layer of skin; connective tissue derived from mesoderm

• hypodermis: deepest layer of integument; connective tissue derived from mesoderm

What is the function of the hypodermis?

connect integument to underlying structures like muscle

Notable features of mammalian skin

• hair

• greater variety of epidermal glands

• thick, cornified epidermis

What is epidermis made of?

stratified squamous, keratinized epithelium (composed of multiple layers of flattened cells; superficial layers are dead & filled with keratin)

Keratin

protein that protects from desiccation

4 epidermis cell types

• keratinocytes

• melanocytes

• langerhans cells

• merkel cells

Keratinocytes

dominant cell type; life cycle determines layers of epidermis

Melanocytes

pigment producing cells; in deep epidermis and superficial dermis

Langerhans cells

phagocytic cells

Merkel cells

touch perception

layers of epidermis; how many are in thin skin? thick skin?

• stratum basale

• stratum spinosum

• stratum granulosum

• stratum lucidum

• stratum corneum

thin: 4

thick: 5

stratum basale

• deepest layer of epidermis

• one layer of keratinocytes undergoing mitosis to produce more cells

  • all keratinocytes in contact with melanocytes to obtain pigment

stratum spinosum

layer of keratinocytes undergoing some mitosis but not as much as basale

stratum granulosum

• 3-5 layers of flattened keratinocytes starting to undergo keratinization

  • more superficial → greater keratinization

  • more superficial → more dead

stratum lucidum

• only in thick skin

• translucent layer of flattened, dead, keratin rich cells

stratum corneum

• most superficial layer of epidermis

• horny layer: made of many layers of flattened, dead, keratin rich cells

  • these cells being continuously shed and replaced

• can inc in thickness due to friction

• gave rise to scales, claws, & horns

Dermis layers

• papillary layer

• reticular layer

Papillary layer

thin superficial layer; made of loose c.t. that nourishes avascular epidermis

Reticular layer

thicker layer; made of dense irregular c.t. that attaches skin to underlying structures

Why is the dermis very well vascularized?

to allow for thermoregulation

What does the hypodermis contain?

• adipocytes (nutrient storage)

• collagen fibers (anchor integument to underlying structures)

• blood vessels

• nerves

Two types of hypodermis

• panniculus adiposus

• panniculus carnosus

Panniculus adiposus

• composed of adipose and lacks muscle fibers

• primary type in humans

• gave rise to blubber in cetaceans & pinnipeds

Panniculus carnosus

• some adipose; mostly skeletal muscle fibers

• moves skin

Cutaneous maximus

muscle of hypodermis that moves skin

Hair

keratinized cutaneous appendage that evolved from epidermal scales

Hair can be divided into:

• shaft: exposed portion

• root: portion embedded in integument

Root sheath

sheath of epidermal cells that surround the root

What makes up the hair follicle?

root + root sheath

Hair bulb

• bulb at base of root that is site of mitosis to produce keratinocytes

• replace shed hairs

Three layers of hair

• cuticle: outermost layer

• cortex: middle layer; contains pigment

• medulla: innermost layer

Structures associated with hair follicle

• sebaceous gland: produces oil

• arrector pili: smooth muscle for thermoregulation & threat displays

• root hair plexus: sensory nerve

Two types of hair in pelt

• underfur

• guard hair

Underfur

• bottom layer

• wool hairs that are shorter, flattened, and curly

• thermoregulation due to insulation

Guard hair

• outer layer

• longer, coarser hairs

• protects underfur from enviro factors

Melanism vs. Leucism

Melanism: heavy pigmentation (ex. black panthers)

Leucism: lack of pigment (white fur)

Awn hair

• third layer that can be found in pelt

• undergoes periodic shedding/molting

Catastrophic Molt

entire skin sloughed off seasonally

Vibrissae

sensory hairs found on muzzles

Quills

modified guard hairs for protective role

Hair scales

scale like structures formed from agglutinized guard hairs

Epidermal glands

• glands of integument

• glands made up of epithelium

• classified as oil, sweat, scent, and milk glands

Sebaceous glands

• alveolar glands that secrete sebum (oil)

• lubricate hair follicles

Sudoriferous glands

• sweat glands

• thermoregulation through evaporational cooling

Two types of sudoriferous glands

• eccrine glands

• apocrine glands

Eccrine glands

• not associated with hair follicle

• only for sweating

• functional throughout life

Apocrine glands

• associated with hair follicles

• release pheromones with sweat

• onset of puberty

Scent glands

• modified integumentary glands for intraspecific chemical communication

• scent marking: used for designating boundaries of territory

Mammary glands

• only in mammals

• produce milk to nourish young

• modified apocrine sudoriferous glands

Milk lines

• mammary glands develop in embryos as milk lines

• pair of ribbons of ectoderm extending from axis to groin

Unguis

curved dorsal plate on claws, nails, and hooves

Subunguis

curved ventral plate; softer

Cuneus

located in U or V shaped portion of hoof

Protractile

claws partially hidden in skin at tip of toe

Nails

modified claws that became flattened for gripping

T/F in most primates the subunguis has been lost

true

Toilet claw

• subunguis redeveloped in prosimian primates

• not true claw

Hooves

• modified claws

• evolved to be principle point of contact between legs and ground

Unguligrade

walking on very tip of hoove

Which digits are the main hooves of artiodactyles?

digit 3 & 4

Dew claws

smaller accessory hooves; typically not used for walking

Perissodactyl hoove patterns

• one hoof: digit 3

• three hooves: digits 2,3,4

Bovine horns

• found in artiodactyl family bovidae

• true horns

• central core of dermal bones covered by sheath of horn

Hair horns

• composed of agglutinized, keratinized, hair-like epidermal fibers

• found in rhinoceros

Antlers

• characteristic feature of family cervidae (deer)

• dermal bone attached to frontal bone of skull

• covered by velvet when growing

• seasonally shed

Velvet

sheath of vascularized skin

Ossicones

• giraffe horns

• solid core of dermal bone that remain ensheathed in velvet throughout lives

• never shed

• both genders have horns

Baleen

• broad, horny sheaths of oral epithelium

• strain food from water

Tori

• epidermal pads on feet of most nonungulate mammals

Apical pads

tori at ends of digits

Axial skeleton

• skull, vertebral column, & rib cage

• protect CNS & support head, neck, and trunk

Skull

• composed of two sets of bones

  • facial: obtaining and processing food

  • cranial: protect and surround brain

Cervical vertebrae

7 vertebrae of neck

Thoracic vertebrae

• vertebrae of upper torso/thorax

• attach to ribs

Lumbar vertebrae

vertebrae of lower torso/back

Sacral vertebrae (Sacrum)

vertebrae attaching to pelvis

Caudal vertebrae

vertebrae of tail

Sternum

anterior point of attachment for ribs via cartilage

Ribs

paired bones that protect thoracic organs

What is pectoral girdle composed of? What does it do?

clavicle & scapula; anchor limb to body

Scapula

articulate with humerus

Clavicle

form brace of pectoral girdle

What is unique about monotremes pectoral girdles?

still include interclavicle

Bones of arm? of forearm?

arm: humerus

forearm: parallel bones; radius & ulna

3 Bones of anterior paw

• carpus: wrist

• metacarpus: palm

• phalanges: digits

Pelvic girdle

anchors posterior limb to body

Pelvis

pair of hip bones + sacrum

Three fused bones in hip bone

• ilium

• ischium

• pubis

What bone do marsupials and monotremes have attached to pubis bone?

epipubic bone (supports pouch in marsupials)

Thigh bone

femur

Patella

knee cap

2 bones in leg

• tibia: weight-bearing

• fibula: slender; for muscle attachment

Bones of posterior paw (pes)

• tarsus: ankle

• metatarsus: 5 small, long bones like palm

• phalanges: digits/toes

Patagium

membrane in bat wings

Plantigrade

• most primitive stance

• palm/sole flat on ground

• monotremes, marsupials, humans, family ursidae, family procyonidae

Digitigrade

• walk on toes of digits 2-5

• 1st digit reduced and not used for walking

• order carnivora

Dew claw

1st digit becomes reduced in size; not used for walking

Unguligrade

• walk on tip of toes with bulk of digit off ground

• claws became hooves

• digits have been lost

Mesaxonic foot

• all 3 digits bear most of weight

• seen in perissodactyls