Histology exam 2

What are the functions of the integument? Include the components that compose each function.

Barrier

• temperature

• water

• pathogen protection

Thermoregulation

• vasodilation→ blood vessels dilate→cool

• vasoconstriction→ blood vessels constrict→ warm

• innervation of dermis (not epidermis)

Secretion and Excretion

• glandular elements

  • sweat glands secrete ammonia

  • sebaceous glands secrete oil

  • mammory glands secrete milk

Species and sex recognition

• males brighter (bold patterns in birds)

Sensory organ

• tactile sensation and pressure sensation

• heat, pain, cold

Identify the 5 layers of epidermis, moving from outermost to innermost layer.

1. Stratum corneum

• hardened, compressed

• stratified squamous 

• “bags” of keratin

• adaption to abrasion

2. Stratum lucidum

• clear band of dead cells with keratin

3. Stratum granulosum

• granules of keratin

• release of lipids (via keratinocytes) which remain in epidermis, lipids called lamellar bodies→ water barrier

4. Stratum spinosum

• desmosomes attach neighbor cells

• allow “stretchiness” quality of skin

• melanin degrades

5. Stratum basale

• adjacent to dermis

• melanocytes→ secrete melanin into environment→ pigment

  • keratinocytes→ phagocytose melanin (stain darker)

Which layer of the epidermis varies in thickness with physical labor? Describe how it can vary.

Stratum corneum can vary in thickness. It is adapted to abrasion and is the tissue that forms calluses out of keratin.

What structures are found in the dermis?

• CT layers

• blood supply via dermal papillae

• innervation

• hair follicles

• glands

What tissue is the primary component of the hypodermis?

adipose CT

In which of the three layers of skin is nervous input found?

Dermis

In what layer of the epidermis are melanocytes found? What is the function of melanocytes?

Stratum basale

They secrete melanin into environment to pigment.

What is the function of desmosomes in the stratum spinosum?

They attach neighboring cells. Allow for the “stretchiness” quality of skin.

How do desmosomes appear microscopically?

white spinish boundaries between keratinocytes

Which layer of the epidermis provides a water barrier?

Stratum granulosum

Keratinocytes release lipids called lamellar bodies that act as water barrier.

Identify the functions of hair.

• insulation

• camouflage

• display 

How does the microscopic appearance of the medulla of a hair differ from the cortex of a hair?

The medulla is the innermost component and not always visible. Cortex is pigmented medulla is light pink.

What is the function of the cuticle of a hair?

protection of hair

What is the function of the dermal papilla of a hair follicle?

It is the entrance and exit of blood vessels.

Distinguish between sebaceous and sweat glands by their function and structure/appearance.

Sebaceous

• empty onto hair

• produces “sebum” for scent and waterproofing

• foamy appearance

Sweat gland

• empties onto skin

• cooling, excretion, scent

• two types- apocrine and eccrine

Distinguish between eccrine and apocrine sweat glands by their secreted products, structure, and anatomic location.

eccrine- excretion, cooling; more uniform and cuboidal

apocrine- odorless fluid secreted onto hair→ encounters microbes that digest sweat to create scent

Describe each of the 3 characteristics of nervous tissue.

• excitable- detects changes in local environment

• conductive- transmit responses to other cells

• secretory- neurotransmitter secreted

Describe tissues that compose the central nervous system compared to the peripheral nervous system.

CNS- brain and spinal

PNS- all other nerves and ganglia

INCOMPLETE

Describe the organization of the peripheral nervous system.

Somatic

• voluntary 

Autonomic

• sympathetic 

  • fight or flight (heart rate, pupil)

• parasympathetic 

  • rest and digest (homeostasis)

Diagram and label a neuron. Indicate the function of each “part.”

Distinguish/ diagram the 3 classifications of neurons. Which type is found in ganglia?

multipolar- 1 axon and many dendrites

bipolar- 1 dendrite and 1 axon

psuedounipolar- found in ganglia 

• integrates and relays sensory and motor

Distinguish between astrocytes and pericytes.

astrocyte

• foot processes

• removes excess neurotransmitters from synapse

• more throughout CNS

• phagocytosis of dead/ dying cells

pericyte

• around capillary

INCOMPLETE

How are oligodendrocytes different from Schwann cells? How are they the same?

oligodendrocyte- 

schwann- 

Describe the location, structure, and function of ependymal cells.

Location

• ventricles of the brain and through spinal cord

• bloo

Structure

• ciliated epitheliated cells 

• columnar and cuboidal

Function

• circulate CSF through ventricles

• works with choroid plexus to synthesize CSF

• wash debris from CNS

• discharged into blood

Why does lipofuscin accumulate in nervous tissue?

INCOMPLETE

Diagram and label how nerves are organized.

Describe the composition and function of the molecular layer of the cerebellum.

Composition

• primarily dendrites of purkinje cells

• basket cells

• medulla 

• cortex

Function

• synapse to inhibit purkinje cells ability to integrate information from two layers

Describe the composition and function of the granular layer of the cerebellum.

Composition

• axons

• granule cells

Function

• granule cells synapse on dendrites of purkinje cells to excite allowing response to signals from cerebellum and spinal cord

How does the structure of Purkinje cells contribute to their integrative function of the other layers?

INCOMPLETE

Where are large motor neurons found? Be specific!

INCOMPLETE

How does the location of grey commissure contribute to it’s function?

integrates both dorsal and ventral horns; found around central canal

Where is the choroid plexus located? What is its function?

INCOMPLETE

synthesizes CSF