Anatomy & Physiology Lecture 2 (Tissues & Integument)

Tissues

groups of similar cells and extracellular material. Four types: epithelial, connective, muscle, nervous. vary in structure and function

Epithelium

one or more layers of closely packed cells

lines an internal or external space. contains little to no EM. covers body surfaces, lines body cavities, forms majority of glands. cells have polarity. Avascular (no blood vessels). Extensive innervation (lots of nerves) and high regeneration capacity. protection, selective permeability, secretions, sensations

Apical surface (epithelium)

lateral surface with intercellular junctions

Basal surface (epithelium)

attached to connective tissue

Simple squamous epithelium

single layer of thin, flat cells; the relatively flat single nucleus of each cell bulges at its center. thinnest possible barrier to allow for rapid diffusion and filtration; secretion in serous membranes. located in air sacs in lungs (alveoli), lining of lumen of blood and lymph vessels (endothelium), serous membranes of body cavities (mesothelium)

Simple cuboidal epithelium

single layer of cells about as tall as they are wide; spherical and centrally located nucleus. absorption and secretion; forms secretory tissue of most glands and small ducts. located in lining of kidney tubules, thyroid gland follicles, surface of ovary, secretory regions, and ducts of exocrine glands

Nonciliated simple columnar epithelium

single layer of nonciliated cells taller than they are wide; oval shaped nucleus oriented lengthwise in basal region of cell. apical surface of cell may have microvilli. may contain goblet cells. absorption and secretion. located in lining of GI/digestive tract

Ciliated simple columnar epithelium

single layer of ciliated cells taller than they are wide; oval shaped nucleus oriented lengthwise in basal region of cell; may contain goblet cells. secretion of mucin and movement of mucus along apical surface of epithelium by cilia. oocyte movement through uterine tube. located in lining of larger bronchioles of the lung and uterine tubes

Ciliated pseudostratified columnar epithelium

single layer of cells with varying heights, all cells connect to the basement membrane but not all reach the apical surface. has goblet cells and cilia. protection; secretion of mucin and movement of mucus along apical surface of epithelium by cilia. located in lining of the larger airways of respiratory tract, nasal cavity, part of pharynx, larynx, trachea, and bronchi

Nonciliated pseudostratified columnar epithelium

single later of cells with varying heights; all cells connect to the basement membrane but not all reach the apical surface. lacks goblet cells and cilia. protection. rare- located in lining of part of the male urethra and epididymis

Keratinized stratified squamous epithelium

multiple cell layers; basal cells are cuboidal or polyhedral and alive, whereas apical cells are squamous, lack a nucleus and organelles, are filled with keratin and are dead. protection of underlying tissue from abrasion. epidermis of skin

nonkeratinized stratified squamous epithelium

multiple cell layers; basal cells are cuboidal or polyhedral, whereas apical cells are squamous. all cells are living, each contains a nucleus and organelles and lacks keratin. superficial cells kept moist. protection of underlying tissue from abrasion. located in lining of oral cavity, part of pharynx, larynx, esophagus, vagina, and anus

Stratified cuboidal epithelium

two or more layers of cells; cells at apical surface are about as tall as they are wide. protection and secretion. located in ducts of most exocrine glands and ovarian follicles.

Stratified columnar epithelium

two or more layers of cells; cells at apical surface are taller than they are wide. protection and secretion. located in large ducts of salivary glands; conjunctiva covering the eye, lining of membranous part of male urethra. cuboidal on top, columnar on bottom

Transitional epithelium

epithelia appearance varies, depending on whether tissue is relaxed or distended (stretched); relaxed has cuboidal or polyhedral cells and the apical cells are large and rounded, whereas distended has flattened cells at apical surface; some cells are binucleated. accommodates urine volume changes in urinary bladder, ureters, and part of urethra.

Endocrine glands

lack ducts. secrete hormones into blood

Exocrine glands

epithelia tissues connected to epithelial space by duct. epithelium lined tube for gland secretion (sweat, mammary, and salivary glands) Classified by number of cells in gland, branched/unbranched duct and shape of duct, and how it releases secretions

Unicellular exocrine glands

• Do not contain a duct

• Located close to epithelium surface

• Most common type is goblet cell

Multicellular exocrine glands

• Numerous cells

• Acini—cells clusters that produce secretions

• Ducts transport secretions to epithelial surface

Simple glands

single unbranched duct

Compound glands

branched duct

Tubular glands

secretory portion and duct are same diameter

Acinar glands

secretory portion forms expanded sac

Tubuloacinar gland

both tubules and acini (cells clusters that produce secretions)

Merocrine glands

package secretions into vesicles, released by exocytosis (lacrimal/tear and salivary glands) exocrine

Apocrine glands

apical membrane pinches off and becomes secretion. (mammary and ceruminous glands) exocrine

Holocrine glands

ruptured cell becomes secretion (sebaceous glands) exocrine

Connective tissue

most diverse, abundant, and widely distributed of the tissue types. originate from mesenchyme of embryonic tissue. vascular but degree varies. wide range of ability to regenerate. All forms share basic components (cells, protein fibers, ground substance)

• Physical protection

• Support and structural framework

• Binding of structures

• Storage

• Transport

• Immune protection

Fibroblast resident cell (CT)

• Most abundant resident cells in CT proper

• Produce fibers and ground substance of

extracellular matrix

Adipocyte resident cell (CT)

fat cells, adipose CT

Mesenchymal resident cell (CT)

embryonic stem cell. divides to replace damaged cells

Fixed macrophages resident cell (CT)

derived from monocytes. phagocytize damaged cells or pathogens

Wandering cells (CT)

repair damaged ECM. diff types of leukocytes, white blood cells. wander out of blood into tissues. protect body from harmful agents.

Collagen protein fibers (CT)

• Unbranched, "cable-like" long fibers

• Numerous in tendons and ligaments

Reticular protein fibers (CT)

• Similar to collagen fibers but thinner

• Abundant in stroma of some organs

(for example lymph node)

Elastic protein fibers (CT)

• Contain protein elastin

• Stretch and recoil easily

• Found in skin, walls of arteries

Ground substance (CT)

Molecular (not cellular) material produced by CT cells

• Residence of CT cells and protein fibers

• Consistency:

• Viscous (for example, blood)

• semisolid (for example, cartilage)

• Solid (for example, bone)

• Ground substance + protein fibers = extracellular matrix

Aerolar loose CT

scattered fibroblasts within an abundant viscous ground substance; few elastic and collage fibers; many blood vessels. protects tissue and organs; binds skin and some epithelia to deeper tissue; provides space for blood vessels and nerves. located in papillary layer of dermis, subcutaneous, surrounds organs, nerve cells, muscle cells, and component of blood vessel walls

Adipose loose CT

closely packed adipocytes; nucleus pushed to edge of cell by large fat droplet; contains many blood vessels. stores energy, insulates, cushions, and protects. located in subcutaneous layer, surrounds and covers some organs

Reticular loose CT

some fibroblasts and numerous leukocytes within a viscous ground substance, meshwork of reticular fibers. provides supportive framework for lymphatic organs. located in spleen, lymph nodes, and red bone marrow

Dense regular CT

fibroblasts squeezed between densely packed, parallel arrays of collagen fibers; scarce ground substance and limited blood vessels. attached bone to bone (ligament) and muscle to bone (tendon); resists stress applied in one direction.

Dense irregular CT

fibroblasts between densely packed but randomly arranged and clumped collagen fibers; more ground substance than in dense regular CT; extensive blood vessels. withstands stresses applied in all directions. durable. located in reticular layer of dermis, epimysium covering skeletal muscle, epineurium covering nerves, periosteum covering bone, perichondrium covering cartilage

Elastic dense CT

limited fibroblasts between densely packed elastic fibers. allows for stretching and recoil. located in walls of elastic arteries, trachea, and vocal chords.

Hyaline cartilage (supporting CT)

irregularly arranged chondrocytes in lacunae; glassy appearing ground substance, collagen fibers not visible. provides support, forms of most fetal skeleton. located in tip of nose, trachea, bronchi, larynx, costal cartilage, epiphyseal plates and articular ends of long bones

Fibrocartilage (supporting CT)

large chondrocytes in lacunae; numerous, parallel collagen fibers; limited ground substance. weight bearing cartilage that resists compression; acts as shock absorber in some joins. Located in intervertebral discs, pubic symphysis, and menisci of knee joints

Elastic cartilage (supporting CT)

closely packed chondrocytes in lacunae; abundant elastic fibers that form weblike mesh; limited ground substance. maintains shape while permitting extensive flexibility. located in external ear and epiglottis of larynx

Bone

• Organic components (collagen and glycoproteins)

• Inorganic components (calcium salts)

• Osteocytes in lacunae

• Levers for movement

• Supports tissues

• Protects vital organs

• Stores minerals, for example, calcium and

phosphorus

• Houses hematopoietic cells (in red bone

marrow of spongy bone), which make blood cells

Compact bone

osteocytes within lacunae entrapped in calcified ECM which contains protein fibers and ground substance; organized in osteons (concentric lamellae, layers of bone matrix, arranged around a central canal- contains blood vessels and nerves). provides levers for body movement, supports soft structures, protects organs, stores calcium and phosphorus

Blood fluid CT

contains formed elements; dissolved protein within a liquid ground substance called plasma. erythrocytes transport respiratory gases. leukocytes help protect the body from infectious agents and platelets help with blood clotting. plasma transports nutrients, wastes, and hormones throughout the body. blood vessels and heart

Skeletal muscle tissue

striated, multinucleated, and voluntary (brain tells to contract). long cylindrical fibers arranged parallel and unbranched. responsible for moving skeleton and thermoregulation. attaches to bone or skin. forms external urethral and anal sphincters

Cardiac muscle tissue

striated, one nucleus, involuntary (rhythmic automatic contraction) short branching cells with intercalated discs. pumps blood through heart in wall and blood vessels

Smooth muscle tissue

not striated, one nucleus, involuntary. short and tapered. moves and propels materials through internal organs; controls the size of lumen. located in walls of internal organs and iris of eye

Nervous tissue

• Located in the brain, spinal cord, and nerves

• Cells called neurons

• Receive, transmit, and process nerve impulses

• Larger number of glial cells

• Do not transmit nerve impulses

• Instead, are responsible for protection, nourishment, and support of neurons

brain spinal cord and nerves

Parts of a neuron

• Cell body

• Nerve cell processes extend from cell body

• Shorter and more numerous processes are called dendrites

• Axon is the single long process extending from the cell body

• Neurons are longest cells in the body

Organs

• Two or more tissue types

• Work together to perform specific complex functions

• Different structures must work in concert

• For example, stomach, contains all four tissue types

Body membranes

• Formed from epithelial layer bound to underlying CT

• Line body cavities and cover viscera and body's

external surface

Four types:

1. Mucous

2. Serous

3. Cutaneous

4. Synovial

Mucous membrane

• Also called a mucosa

• Lines compartments that open to external

environment

• Includes: digestive, respiratory, urinary, and reproductive tracts

• Performs absorptive, protective, and secretory functions

• Formed from epithelium and underlying CT

Serous membrane

• Lines body cavities that do not open to external

environment

• Simple squamous epithelium

• Produces thin, watery serous fluid

• Derived from blood plasma

• Reduces friction between opposing surfaces

• Forms parietal and visceral layers

• Serous cavity is in between

Cutaneous membrane

• Aka- skin

• Covers external surface of body

• Composed of

• Keratinized stratified squamous epithelium

• Underlying CT

• Protects internal organs and prevents water loss

Synovial membrane

• Lines some joints in body

• Composed of Areolar CT

• Covered by squamous epithelial cells lacking

basement membrane

• Synovial fluid secreted by epithelial cells

• Reduces friction among moving bone parts

• Distributes nutrients to cartilage

Hypertrophy

increase in size of existing cells of a tissue

Hyperplasia

increase in the number of cells of a tissue

Atrophy

• Shrinkage of tissue by decrease in cell number or size

• Due to normal aging or disuse

Metaplasia

• Change of mature epithelium to a different form (e.g. smokers)

• May occur as epithelium adapts to environment

Dysplasia

• Abnormal tissue development

• May be precancerous

Neoplasia

• Tissue growth is out of control

• Neoplasm (tumor) of abnormal tissue develops

• Benign or malignant

Necrosis

• Tissue death

• Due to irreversible tissue damage (e.g. gangrene)

Embryonic stem cells

originate from the dividing cells of the zygote or embryoblast portion of blastocyst. may be totipotent(can give rise to every differentiated cell) or pluripotent(derived from embryoblast and can specialize into a cell within any tissue except placenta)

Adult stem cells

undifferentiated stem cells in the body after birth. may be multipotent(restricted number of cell types) or unipotent(a single type of cell)

Tissue aging

All tissues change with aging

• Structure and chemical composition of many tissues

altered

• Epithelia thins

• CT loses pliability and resiliency

• Collagen declines

• Bones become brittle

• Muscles atrophy

Integumentary system

covers body and consists of skin and accessary tissues (nails, hair, sweat glands, sebaceous glands)

integument= skin (organ)

cutaneous membrane

Epidermis

composed of keratinized stratified squamous epithelium.

• Layers (strata) from deep to superficial:

1. Stratum basale

2. Stratum spinosum

3. Stratum granulosum

4. Stratum lucidum*

5. Stratum corneum

• First three layers composed of living keratinocytes

Stratum

(1) deepest epidermal layer. Single layer of cuboidal to low columnar cells

• Three cell types:

1.Keratinocytes

2.Melanocytes

3.Tactile cells

Keratinocytes

most abundant skin cell; synthesizes keratin

• Found in all layers

• Those in stratum basale are large stem cells

Melanocytes

• Scattered among keratinocytes

in stratum basale

• Produce and store pigment

(melanin) in response to

ultraviolet light

• Transfer pigment granules

(melanosomes) into

keratinocytes

• Shield nuclear DNA from UV radiation

Tactile cells

Sensitive to touch. in stratum basale layer

• When compressed,

release chemicals,

stimulate sensory nerve

endings

Stratum spinosum

(2) Several layers of

polygonal keratinocytes

• Nondividing keratinocytes

attached by desmosomes

• Epidermal dendritic

cells (Langerhans cells)

found in stratum

spinosum and

granulosum

• Initiate immune response

Stratum granulosum

(3) 3 to 5 layers of keratinocytes

• Keratinocytes begin keratinization

Stratum lucidum

(4) found only in thick skin. translucent layer, 2-3 cell layers thick

Stratum corneum

(5) Superficial stratum composed of 20 to 30 layers of dead,

interlocking, anucleate (lacking a nucleus), keratinized

cells. closest to external

Thick skin

• Palms of hands, soles of feet

• Contains all five layers of epidermal strata

• Sweat glands but no hair follicles or sebaceous glands

Thin skin

• Covers most of body

• Lacks a stratum lucidum

• Sweat glands, hair follicles, and sebaceous glands

Hemoglobin

Oxygen-binding protein in red blood cells

• Gives skin pink color upon binding oxygen

Melanin

• Dark pigment produced in melanocytes, transferred

to keratinocytes

• Eumelanin - brown, black shades; pheomelanin - lighter

shades: tan, yellow, red

• Amount in skin varies (heredity, UV exposure)

Albinism

melanocytes unable to produce melanin

Carotene

Yellow-orange pigment acquired from some vegetables

Nevus

mole- Localized overgrowth of melanocytes

• Should be monitored for changes suggesting malignancy

Freckles

• Yellowish or brown spots

• Localized areas of increased melanocyte activity

Hemangiomas

Skin discoloration due to benign blood vessel tumor

Dermis

• Deep to epidermis

• Composed of CT proper

• Other structures present: Blood vessels, sweat

glands, sebaceous glands, hair follicles, nail roots,

sensory nerve endings, arrector pili, motile

dendritic cells

• Two layers:

• Papillary and reticular layers

Papillary layer (dermis)

• Superficial region of dermis, deep to epidermis

• Friction ridges - large folds and valleys of dermis and

epidermis; results in fingerprints

• Areolar connective tissue

• Named for projections of dermis, dermal papillae

Reticular layer (dermis)

Deeper, major portion of dermis

• Dense irregular connective tissue

Lines of cleavage (tension lines)

Collagen and elastic fibers oriented in parallel bundles

at specific locations

• Bundles function to resist stress during routine movement

• Incisions

• If skin stretched beyond its capabilities

• Some collagen fibers torn, results in stretch marks

(striae)

Tattoos

• Permanent images produced on integument

• Dye injected into dermis

• Permanent part of dermis layer

• Usually impossible to completely remove a tattoo

• Lasers used to break down pigments

• Newer inks are available that allow for removal

Subcutaneous layer

(hypodermis, superficial fascia)

• Not part of integument

• Areolar and adipose CT

• Functions: Protection, energy storage, and insulation

• Common drug injection site

• Extensive vascular network promotes rapid absorption

• Thickness/distribution influenced by sex hormones

Functions of integument

Protection from the external environment

• Injury, harmful substances, microbes, extreme

temperatures, and UV radiation

Prevention of water loss/gain

• Epidermis is water resistant, not waterproof

• Water lost by sweat and transpiration

Vitamin D synthesis

• Formation of vitamin D3, a precursor to calcitriol

( increases absorption of calcium and phosphate from diet;

regulates blood calcium levels)

Secretion

• Waste products secreted onto skin surface during sweating

Absorption

• Skin absorbs some chemicals/drugs but blocks others

• Selectively permeable

• Suitable for transdermal administration of some drugs

Immune function

• Dendritic cells in epidermis and dermis capable of initiating immune

response

Temperature regulation

• Dermal blood vessels capable of vasoconstriction to conserve heat

or vasodilation to release heat

Sensory reception

• Receptors detect stimuli (e.g., touch, pressure)

Nails

scale like modifications of the stratum basale.

Structure of nails

• Protect distal tips of digits and assist in grasping objects

• Distal whitish free edge (no underlying capillaries)

• Pinkish nail body (underlying capillaries)

• Nail folds

• Folds of skin overlapping nail

• Eponychium (cuticle)

• Narrow band of epidermis from margin of nail wall onto nail body

Lunula

whitish semilunar area on proximal end of nail body

Nail bed

Layer of living epidermis covered by

nail body

Nail root

part of nail embedded in skin