The Integumentary System

The Integumentary System

Integument is skin Skin and its appendages make up the

integumentary system A fatty layer (hypodermis) lies deep to it Two distinct regions

EpidermisDermis

Functions of skin

Protection Cushions and insulates and is waterproof Protects from chemicals, heat, cold, bacteria Screens UV

Synthesizes vitamin D with UV Regulates body heat Prevents unnecessary water loss Sensory reception (nerve endings)

Epidermis

Four types of cells Keratinocytes – deepest, produce keratin (tough fibrous protein) Melanocytes - make dark skin pigment melanin Merkel cells – associated with sensory nerve endings

Layers (from deep to superficial) Stratum basale or germinativum – single row of cells attached

to dermis; youngest cells Stratum spinosum – spinyness is artifactual; tonofilaments (bundles of protein)

resist tension Stratum granulosum – layers of flattened keratinocytes producing keratin (hair and

nails made of it also) Stratum corneum – horny layer (cells dead, many layers

thick)

(see figure on next slide)

Epithelium: layers (on left) and cell types (on right)

Remember…

Four basic types of tissue

Epithelium – epidermis just discussedConnective tissue - dermisMuscle tissueNervous tissue

Dermis Strong, flexible connective tissue: your “hide” Cells: fibroblasts, macrophages, mast cells,

WBCs Fiber types: collagen, elastic, reticular Rich supply of nerves and vessels Critical role in temperature regulation (the

vessels) Two layers (see next slides)

Papillary – areolar connective tissue; includes dermal papillae

Reticular – “reticulum” (network) of collagen and reticular fibers

*Dermis layers

*

*

*Dermal papillae

Epidermis and dermis of (a) thick skin and (b) thin skin(which one makes the difference?)

Hypodermis

“Hypodermis” (Gk) = below the skin “Subcutaneous” (Latin) = below the skin Also called “superficial fascia”

“fascia” (Latin) =band; in anatomy: sheet of connective tissue

Fatty tissue which stores fat and anchors skin (areolar tissue and adipose cells)

Different patterns of accumulation

(male/female)

Skin color Three skin pigments

Melanin: the most importantCarotene: from carrots and yellow vegiesHemoglobin: the pink of light skin

Melanin in granules passes from melanocytes (same number in all races) to keratinocytes in stratum basaleDigested by lysosomesVariations in colorProtection from UV light vs vitamin D?

Skin appendages

Derived from epidermis but extend into dermis

IncludeHair and hair folliclesSebaceous (oil) glandsSweat (sudoiferous) glandsNails

Nails

Of hard keratin Corresponds to hooves and claws Grows from nail matrix

Hair and hair follicles: complexDerived from epidermis and dermisEverywhere but palms, soles, nipples, parts of genitalia

*“arrector pili” is smooth muscle

*

Hair papilla is connective tissue________________

Hair bulb: epithelial cells surrounding papilla

Functions of hairWarmth – less in man than other mammalsSense light touch of the skinProtection - scalp

PartsRoot imbedded in skinShaft projecting above skin surface

Make up of hair – hard keratin Three concentric layers

Medulla (core)Cortex (surrounds medulla)Cuticle (single layers, overlapping)

Sweat glands Entire skin surface

except nipples and part of external genitalia

Prevent overheating 500 cc to 12 l/day!

(is mostly water) Humans most

efficient (only mammals have)

Produced in response to stress as well as heat

Review What are the top and

bottom layers of the epidermis

What are the 4 cell types within the epidermis

What structures reside in the dermis?

The role that the integumentary system plays?

Order these skin layers superficial to deep: dermis, hypodermis, epidermis.

Where might you find keratin?

Dissecting the Fetal Pig

Sus scrofa

Introduction to Mammals

Of all the classes of animal life, mammals are considered to be the most advanced.

Examples: dogs, cats, squirrels, pigs, whales, horses, sheep, and HUMANS!

Vary greatly in size…from 2 inches (the shrew) to 100 feet long (the blue whale)

Mammalian Characteristics Vertebrates (have

backbones) Presence of lungs

(breathe air) Warm-blooded

(endothermic)This means that the body

temperature of a mammal stays the same, no matter what the outside temperature is

4 chambered heart

Mammalian Characteristics, cont’d

Give birth to live youngMonotremes – mammals

that lay eggsEX: the platypus and

the echidna (spiny anteater)

Body Hair Produce milk (have

mammary glands)

Platypus

Echidna

Mammalian Characteristics, con’t

Less Obvious CharacteristicsThe diaphragm separates

the heart and lungs from the stomach

Lower jaw has one bone on each side

Different types of teeth adapted to different uses (tearing, chewing)

Brains are much more highly developed than any other animal

Comparative Anatomy

Study of similarities and differences in the anatomy (structure) of organisms

Many aspects of structure and function are identical between different species of mammalsHomologous Structures – same structure

(embryologically speaking), different function (have a common evolutionary descent)

EX: wings of bats and arms of humansAnalogous Structures – different structure, same function

(evolved in a similar environment) EX: wings of bats and wings of insects

Comparative Anatomy

Fetal Pigs Humans

Kingdom Animalia Animalia

Phylum Chordata Chordata

Class Mammalia Mammalia

Order Artiodactyla Primates

Family Suidae Hominidae

Genus Sus Homo

Species Scrofa sapiens

Why Fetal Pigs?

The fetal pig is a mammal, like humans. Nearly all the structures are the same or very similar in anatomy.

Fetal pigs are NOT bred for the purpose of dissection. They are a by-product of the pork food industry.

Fetal pigs are NOT killed for the purpose of dissection. Those that are not dissected are used for fertilizer or discarded.

Fetal pigs are relatively inexpensive. Even in the extra large size, when the structures are well-developed, they can be obtained for about 1/3 the cost of a similarly sized cat.

Most people do not think of pigs as “pets.”

Advantages to Dissection

Dissection is a hands-on, investigatory kind of activity for students. Dissection allows students to "test the truthfulness" of what they see in books.

Dissection impresses on students the normal variation that is present in the natural world. No two fetal pigs, even though they are perfectly normal, will look exactly the same.

In fact, to do well on practicals, students MUST looks at several examples of each structure in different animals. Occasionally, quite significant anatomical variations (anomalies) will be noticed.

Safety and Handling Sharps

All Dissecting tools should be considered dangerous.

Notify your teacher IMMEDIATELY if you are cut.

Handle probes, dissection scissors, razor blades, etc. with extreme caution.

Always cut away from you, never toward yourself or another person.

Dissection specimens should be properly mounted in the dissection pan before cutting.

Safety and Handling, cont’d

Do not place your hands near your mouth or eyes while handling preserved specimens.  Most of the preservatives in use today are non-toxic to the skin, but they may cause minor skin irritations.  If the preservative gets on your skin, wash with soap and warm water.

If the preservative gets in your eyes, rinse them thoroughly with the safety eyewash.

Wear lab gloves and goggles at all times! Lab gloves and paper towels go in

the regular trash.  Skin and pieces of pig go into the separate plastic bag at the front of the room (NOT down the sink).

Dissection Helpful Points Actual cutting should be kept to a

MINIMUM Tissue are picked and teased

apart with needle probes, forceps, and blunt probes in order to trace the pathways of blood vessels, nerves, muscles, and other structures.

NEVER CUT OR MOVE MORE THAN IS NECESSARY TO EXPOSE A GIVEN PART.

Compare dissections with other students, especially students whose pig is of a different sex. You will be responsible for both sexes on the lab practical (test).

Determine the Sex of your Pig• Female:  Look for a single urogenital opening

just ventral to the anus.  A prominent genital papilla projects from the urogenital opening. 

• Male:  Look for the scrotum, a sac-like swelling containing the testes and located ventral to the anus.  The male urogenital opening is faintly visible just posterior to the umbilicus.  Note that males as well as females have multiple nipples = teats = mammary papillae.

Female Male