Unit 2 Exam

Tissue

Group of similar cells that perform a common function

Types of Tissues:

Epithelial, Connective, Nervous, Muscular

Characteristics of Epithelial Tissue

Closely fit by tight junctions

Apical (free) Surface

Basement membrane

Avascular

Highly sensitive

Types of Epithelial Tissue

Simple squamous, simple cuboidal, simple columnar, stratified squamous, stratified cuboidal, pseudostratified columnar

Simple VS. Stratified

Simple: single layer

Stratified: multiple layers

Simple Squamous

• Single layer of flat cells.

• Function: Rapid diffusion of substances .Secretes serous fluid

• Location: Alveoli in lungs, Capillaries, Serous membranes

Simple Cuboidal

• Single layer of cube shaped cells

• Absorption and secretion

• Thyroid gland

Simple Columnar

• Single layer of columnar cells: May have cilia and goblet cells

• Absorption and secretion: Goblet cells secrete mucus

• Lines the gastrointestinal tract (ex. Intestines)

Pseudostratified Columnar

• Single layer of columnar cells: Cells of different heights with nuclei at

different levels makes it appear stratified. May have cilia and goblet cells

• Cilia propel mucus, goblet cells secrete mucus

• Lines the respiratory tract (Trachea and bronchi)

Stratified Squamous Keratinized

• Multiple cell layers with dead cells that are flat and scaly at surface

• Resists mechanical injury (abrasion), prevents water loss through skin; resists

penetration by pathogenic organisms

• Epidermis of skin

Stratified Squamous Non-Keratinized

• Same as keratinized epithelium without the surface layer of dead cells

• Resists mechanical injury (not as much as keratinized though) and penetration

of pathogenic organisms

• Tongue, oral mucosa, esophagus

Transitional

• Multiple cell layers, surface cells change from round to flat when stretched

• Allows an organ to distend for filling

• Ureters and urinary bladder

Connective Tissue Characteristics

Highly vascular

Composed of cells and extracellular matrix

Extra Cellular Matrix

Made of ground substance and fibers

• Ground substance: very small, gelatinous

• Fibers: Three types of fibers

Collagen: Strength

Reticular: support

Elastic: allow stretch and recoil

Types of Connective Tissue

• Connective Tissue Proper (Fibrous): Loose & Dense

• Bone

• Cartilage

• Blood

Types of Loose Fibrous CT

Areolar, Adipose, Reticular

Areolar CT

Fibroblasts, collagen, elastic, and reticular fibers in matrix

Connects tissues and organs

Papillary layer in dermis of skin

Allows space for edema

Adipose CT

• Empty-looking cells with nucleus pressed against cell membrane

• Adipocytes are fat cells filled with triglycerides

• Energy storage, cushions organs

• Hypodermis (subcutaneous layer of skin: what we typically call

our fat) and around the heart and kidneys

Reticular CT

• Mesh of short intertwining fibers and fibroblasts

• Supportive framework for lymphatic organs

• Lymph nodes and spleen

Types of Dense CT

Regular & Irregular

Dense Regular CT

• Densely packed, parallel collagen fibers

• Provides tensile strength in one plane of movement

• Tendons attach muscles to bones, ligaments hold bones together

Dense Irregular CT

• Densely packed, randomly arranged collagen fibers and few visible cells

• Withstandlas stresses in different directions

• Reticular dermis of skin

Cartilage

• Supportive connective tissue with flexible, rubbery matrix

• Main cell is chondrocytes

• Fibers differ with type of cartilage

Types of Cartilage

Hyaline, Elastic, Fibrocartilage

Hyaline Cartialge

• Chondrocytes surrounded by clear, glassy matrix

• Creates smooth surface for joint movement

Keeps airways open

• Articular cartilage at end of long bones

Trachea

Elastic Cartilage

• Chondrocytes surrounded by elastic fibers

• Provides flexibility and stretch

• External ear

Tip of nose

Fibrocartilage Cartilage

• Chondrocytes surrounded by thick bundles of collagen fibers

• Shock absorption

• Pubic symphysis, intervertebral discs

Blood CT

• Fluid connective tissue:

Plasma is the matrix.

Contains RBCs, leukocytes,

and platelets

• Transports oxygen, nutrients, hormones, and removes wastes

• Inside heart and blood vessels

Nervous Tissue

• Nervous tissue is found in brain, spinal cord and nerves.

• Main function is to receive stimuli from body and send back responses.

• Cells in nervous tissue are neurons and neuroglia

Neurons

• Cell body with many extensions

• Conduct nerve impulses

• Brain, spinal cord, nerves

Neuroglia

• Many different types

• Protect and assist neuron

• Brain, spinal cord, nerves

Types of Muscular Tissue

Skeletal, Cardiac, Smooth

Skeletal Tissue

• Long cylindrical cells (muscle

fibers)

Multiple nuclei per cell

Striations: alternating dark and

light bands

Voluntary: conscious control

• Attach to bone

Responsible for

movement

• Skeletal muscles

Muscles of the face

Smooth Muscle Tissue

• Short fusiform cells (thick in middle, tapered at ends)

One centrally located nucleus

Unstriated and involuntary

• Propels contents through an organ

Changes diameter of blood vessels

• Wall of digestive and urinary tract

Walls of blood vessels

Cardiac Muscle

• Short and branched

One centrally located nucleus

Intercalated discs join cardiac muscle cells

Striated and involuntary

• Contraction of cardiac muscle will pump blood to body organs

• Located only in the heart

Glandular Epithelial

ET that secretes substances

Endocrine Glandular ET

• Secrete into bloodstream. They are ductless glands.

• Endocrine glands secrete hormones. They are few in number.

• Example: Thyroid and adrenal glands

Exocrine Glandular ET

• Secrete out to the surface by a duct.

• Very numerous

• Example: Sweat glands

Types of Cell Junctions

Tight Junctions: seal cells together to prevent passage of water or ions: Ex. Blood brain barrier and epithelium lining urinary bladder

Gap Junctions: membrane proteins form tunnels that allow ions to pass from one cell to the other. Allows rapid spread of electrical signals. Ex. Cardiac muscle, skeletal muscle

Adhesion (desmosome) junctions: anchor adjacent cells that are subjected to mechanical stress. Ex. Cardiac muscle

Layers of Skin

Epidermis, Dermis, Hypodermis

Epidermis

• Keratinized stratified squamous epithelium

• Thickness of the epidermis determines whether skin is “thick” or “thin”

Dermis

Two layers

• Papillary layer

Areolar connective tissue

• Reticular layer

Dense irregular connective tissue

Hypodermis

• Not a part of the skin, but usually studied with the skin

• Adipose connective tissue (subcutaneous fat)

Thick Skin

on palms and soles, fingers and toes

• Has sweat glands, but no hair follicles or sebaceous (oil) glands

• Epidermis is thicker

Thin Skin

covers rest of the body

• Possesses hair follicles, sebaceous glands, and sweat glands

5 layers of epidermis (bottom to top)

Stratum basale

Stratum Spinosum

Stratum granulosum

Stratum lucidum

Stratum corneum

Stratum basale

Single layer of stem cells. Scattered melanocytes and Merkel cells

Stratum spinosum

Keratinocyte attachments appear spiny. Few dendritic cells

Stratum granulosum

Granular keratinocytes

Stratum lucidum

only in thick skin. No nucleus or organelles

Stratum corneum

dead keratinocytes flaking away

Cells in epidermis

stem, melanocytes, merkel, keratinocytes, dendritic/langerhans

Stem cells

mitotic dividing cells that produce keratinocytes

Melanocytes

synthesize the pigment melanin. Shields DNA of cells from UV radiation

merkel cells

touch receptors

Keratinocytes

squamous “skin cells” - synthesize keratin

Dendritic/langerhans cells

macrophage - perform phagocytosis of harmful pathogens or toxins

Layers of dermis

Papillary, Reticular

Papillary Layer

• Superficial layer composed of areolar tissue

• Contains dermal papillae

Dermal papillae

upward fingerlike extensions of the dermis. They fit into epidermal ridges on fingertips that leave fingerprints.

Reticular Layer

Deeper and thicker layer composed of dense irregular CT

Structures in Dermis

Meissner’s corpuscles, free nerve endings, sweat glands, sebaceous glands, Pacinian corpuscles, hair bulbs

Meissners corpuscles

touch receptors

Pacinian corpuscles

pressure receptors

Hair bulbs

located in dermis but they originate from epidermis

3 layers of hair from root to out

Medulla, Cortex, Cuticle

Arrector pili muscle

muscle attached to hair bulb; Bundles of smooth muscle cells - contract to cause goose bumps

Skin glands

Sudoriferous, sebaceous

Sudoriferous gland

Sweat gland; • Eccrine (merocrine) sweat glands - duct to skin surface

• Apocrine sweat glands - duct to hair follicle

• Sweat is mostly water and minerals. It is slightly acidic which

inhibits overgrowth of bacteria.

Sebaceous gland

oil

Hemoglobin

Red pigment

Carotene

yellow pigment

Pallor

decreased blood flow to skin makes more white

Emotional stress, low blood pressure, circulatory shock, cold, anemia

Cyanosis

bluish discoloration from deficiency of oxygen.

Airway obstruction (drowning or choking) and lung diseases (emphysema)

Jaundice

yellowish discoloration of skin and sclera due to excess of bilirubin in blood

Cancer, hepatitis, compromised liver function

Basal cell carcinoma

- Most common type

- Least dangerous because it seldom metastasizes

- Forms from cells in stratum basale

Squamos cell carcinoma

- Arise from keratinocytes in stratum spinosum

- Lesions appear on scalp, ears, lower lip, or back of the hand

- Have raised, reddened, scaly appearance later forming a concave

ulcer

- Chance of recovery good with early detection and surgical removal

- Tends to metastasize to lymph nodes and may become lethal

Malignant melanoma

- Skin cancer from melanocytes; often in a preexisting mole

- Less than 5% of skin cancers, but most deadly form

- Treated surgically if caught early

- Metastasizes rapidly; unresponsive to chemotherapy; usually fatal

- High incidence in men, redheads, people who experience severe

sunburn in childhood

Hair bulb

swelling at base. Contains

Matrix: mitotically active cells

Papilla: blood vessels for nutrition

Hair receptors

• Nerve fibers that entwine each

follicle

• Respond to hair movement

Piloerector muscle (arrector pili)

• Bundles of smooth muscle cells

• Goose bumps

Types of tissue repair

Regeneration, Fibrosis

Regeneration tissue repair

replacement of dead or damaged cells by the same type of cell as before

• Restores normal function

• Skin injuries and liver regenerate

Fibrosis

replacement of damaged cells with scar tissue

• Holds organs together

• Does not restore normal function

• Severe cuts and burns, healing of muscle injuries

Dep dermal tissue repair

Hemostasis: Severed blood vessels will make a clot closing the gap. The surface will harden and form a scab to seal

Organization: beneath the scab, macrophages will gradually digest the blood clot

Granulation tissue: Fibroblasts lay down collagen fibers and new blood vessels restore circulation.

Maturation and Regeneration : The fibrosed area will mature and contract. Surface epithelium will divide and regenerate.

Function of nervous system

• Sensory input: Gathering information. Monitoring changes in and outside

body. Sense organs detect stimuli and send signals to the brain and spinal cord.

• Integration: Process and interpret sensory input to determine appropriate

response

• Motor output: Response to stimuli. Send commands to activate muscles or

glands in response to the input

Central Nervous System

Brain + Spinal Cord

Peripheral nervous system

Cranial nerves + spinal nerves

Neurons

Actual nerve cells that transmit signals

Neuroglia

Support system for the neurons

Soma (cell body)

Contains organelles except centrioles (no cell division). Metabolic functions

Dendrites

Receptive: receives stimuli from other neurons

They convey stimuli to the soma by graded potentials.

Axon

Axon hillock: Nerve impulse (action potential) is generated in the trigger zone.

Impulse travels down the axon

Axon: conducting area. Will conduct the action potential to the terminal

Axon terminal

Secretory area. Terminal branches have knobs containing synaptic vesicles of

neurotransmitters.

Organization of Peripheral nervous system

Somatic, visceral

Somatic

Signals from skin, muscles, joints. Response to

skeletal muscles

Visceral

signals from viscera (internal organs). Response to

cardiac muscle, smooth muscle and glands

Myelination

• Myelin sheath is an insulating layer of material that is mostly lipid.

• Myelinating glia wrap several layers of myelin around the cell membrane of

a segment of the axon.

• Schwann cells insulate peripheral nerves while oligodendrocytes insulate

the CNS.

• Areas not covered with myelin are called nodes of Ranvier

Synapse

The synapse is a connection

between two neurons. It transmits

signals between neurons

Presynaptic neuron

axon bulges to form synaptic knob that contains synaptic vesicles which store neurotransmitter (Acetylcholine)