Surface Membrane & Connective Tissue Support Flashcards
Characteristics of epithelia
Highly regenerative Avascular Highly innervated Almost always associated with CT Immediately adjacent to basal surface
Surface Membranes
Major Function
Physical barrier!
First line of defense
Physical barriers
Function and examples
Non-specific means of defense
Impede damage by “sealing it off” from environment
Regulate how other tissues communicate with foreign matierial
Ex:
Epidermis of skin
Mucous membranes
Cellular secretions (tears, earwax, mucus, stomach acid)
Physical barriers
Trade offs
Any membrane can be considered a coating, which leaves tissues/organs vulnerable if exposed
Some are more mechanically protective (based on thickness)
Thick membranes may secrete, but then don’t likely absorb well
If they actively pump substances, may have ample cytoplasm
Order of defense
Physical barrier
Cells in CT
…
Immune system
The environment is…
both outside and within us
If entirely passive transport occurs, what type of epithelia is it?
Simple Squamos Epithelium
Ex: capillaries
Non-specific means of defense
Occurs before immune system is activated.
1 - surface membrane
2 - white blood cells
3 - lymphocytes
What are the main cellular components of the immune system?
Lymphocytes
Neutrophils
Overview
Non-specific, even if they specialize in some functions
Respond to inflammatory insult
Capable of phagocytosis of bacteria
Cellular means of defense
Innate immune system
Includes neutrophils and other leucocytes
Neutrophils
Actions
“Bacteria specialists”
Produce signals that augment repair
Rich source of prostaglandin (to facilitate mucosal repair)
Circulate in blood
Normally most numerous of leukocytes in CT & epithelia
Basement membrane components
Basil lamina and reticular lamina
Adaptive immune system
Targeted activity of lymphocytes
CT
General
Very broad tissue category in micro-anatomy
Physically tough
Types of CT
Bone Cartilage Ligaments Soft (adipose) Fluid (blood)
General functions of CT
Structure
Metabolic
Immune defense
Mechanical functions of CT
Provide support to body
Facilitate movement
Metabolic functions of CT
Most CT is very vascular, but blood is avascular.
Metabolic needs are borne by blood vessels within the supporting CT
Defense functions of cT
Contain many blood vessels specialized for defense
Cells are capable of migrating into CT
Cells patrol the regions deep to epithelial boundaries
The integument layers
Three:
Outermost - Physical barrier
Outer layer - Epidermis
Inner layer - Dermis
Outermost physical barrier
Definition
Most external boundary between internal and environment
Protective
Serves as site of absorption, excretion, or sensory output and uptake
Outermost physical barrier
Composed of epidermis and dermis
Papillae present at junction between layers
Two categories of thickness:
Thick
Thin
Papillae
Projections of the dermis at the junction between layers
Help the adherence (distribute tension) to epidermis
Thick skin
Rougher
Smooth (except for ridges like fingerprints)
Hairless
Ex: palms, soles of feet
Thin skin
Hairy Found elsewhere (not palms or soles of feet)
Epidermis
Characteristics & type
Outer layer
Epithelial component
Avascular
Has cell types within
Has five layers, deep to superficial
Stratisfied squamous epithelium
Dermis
Connective tissue component
Has many cell types (fibroblasts, fat cells, smooth muscle cells)
Highly vascular
Resilient leather or hide
Has two layers: papillary and reticular
Protective characteristics of Epidermis
High degree stratification
Phagocyte
Cellular products
Dead surface layer
Cells types of Epidermis
Keratinocytes
Melanocytes
Merkel cells
Langerhans cells
Keratinocytes
Manufacture keratin
Melanocytes
Contain pigments
Gives skin it’s color
Merkel cells
Present in small numbers
Located at epidermal - dermal junction
Flat bottomed discs
Directly communicate with afferent (sensory) nerve endings
Merkel discs = light pressure mechanoreceptors
Langerhan’s cells
Macrophages
2-8% of epidermal population
Derived from bone marrow
Can bind antigens for presentation to T-cells
Keratin
A tough waterproof protein Manufactured by keratinocytes Forms basis for: Outer epidermis Nails Hair
Five layers of the Epidermis
Deep to Superficial: Stratum Basale Straum Spinosum Stratum Granulosum Stratum Lucidum Stratum Corneum
Stratum Basale
Deepest layer of epidermis
Germinativum
Cells which divide and multiply
The source of cells for more superficial layers
Mostly keratinocytes and melanocytes
Numerous desmosomes bind cells to one another
Straum Spinosum
Above the stratum basale of epidermis
Maturing cells
Spiny in preparation due to shrinkage while desmosomes hold
Has tension-resistant protein filaments
Langerhans cells migrate in from bone marrow (act as macrophages)
Has Malpighian layer
Stratum Granulosum
Above the stratus spinosum of epidermis
Cells contain keratohyalin granules (basophilic)
Cells above this layer are relatively nutrient starved (aka dead)
Stratum Lucidum
Above the stratum lucidum of epidermis Dead cells which had produced keratin fibrils from keratohyalin and filaments fill the cells No organelles are seen Desmosomes still seen Can be absent or the thinnest Appear lucid or clear
Stratum Corneum
Most superficial layer of epidermis
Layer of dead keratinocytes and glycolipid
Usually 15-20 cells thick (can be up to 30)
Keratin fills the cells - serves to protect and insulate
Cells are cornified
Thinner layer then stratum lucidum
Malpighian layer
Consists of the stratum basale and spinosum
The ONLY area of mitoses (active cell sites)
Keratohyalin granules (basophilic)
Important components of keratin and lamellar granules
Act to conserve moisture
Act as barrier against antigens
Sensory structures in dermis
Meissner’s corpuscles
Pacinian corpuscles
Meissner’s corpuscles
Sensory structure in dermis
Located in dermal papillae of hairless skin
Function as mechanoreceptors for light pressure, discriminant touch (rolling of fingertips)
Especially fingertips, eyelids, nipples, external genitalia
Pacinian corpuscles
Sensory structure in dermis
Located in subcutaneous tissue of skin
Function as mechanoreceptors for deep pressure, stretch
Most abundant in fingers, soles of feet, external genitalia, nipples
Loose CT vs. Dense CT
Loose: more superficial, has more cells here
Dense: irregular, dense, has collagen bundles, deeper!
Early phases of healing in epidermis and skin
Microscopic view
First will notice inflammation then black dots (white blood cells)
Two layers of dermis
Papillary layer
Reticular layer
Hypodermis
Deeper tissue to the dermis NOT part of integument Loose CT Adipose tissue Capillary bed sources are here
Papillary layer
One of two layers in dermis Most superficial Thin Dermal papillae which project into stratum basale Contains blood vessels Nerve endings Lymphatics (loose CT, most vascular)
Reticular layer
One of two layers in dermis Deeper Thicker Thick collagen Elastic fiber bundles Contains sweat glands Contains hair follicles
Where are hair follicles formed?
Epidermis
What are the keratin derivatives?
Hair
Nails
Hair
Keratinized cells
Produced by hair follicles
Hair root shafts consist of central medulla & outer cuticle
Initially fine and androgen influence at puberty
Nails
Hardened modifications of epidermis
Nail matrix is actively growing region
Melanin
Produces hair color
Hair follicles
Consist of inner epidermal root sheaths Enclose matrixes Well vascularized Innervated Arrector pili muscles Pull follicles to upright position (goose bumps)
What muscles produce goose bumps?
Arrector pili muscles
Pull follicles to upright position (goose bumps)
Factors reflecting hair thinning
Follicular resting pds
Age related follicle atrophy
Genetics
Glands in dermis
Sebaceous Eccrine Apocrine Scent and wax Mammary
Sebaceous glands
Glands in dermis
Usually opening onto hair follicles
Secrete sebum (waxy secretions)
Not found on palm or sole of feet
Eccrine glands
Glands in dermis
Coiled
Allow for thermoregulation
Apocrine sweat glands
Glands in dermis
More thick and odorous secretion than eccrine glands
Release waste
Scent and wax glands
Modified apocrine glands
Mammary glands
Modified sweat glands
Mucosae
Organization
Similarity to Integument
Include:
Epithelial part AND connective tissue deep to it
Similar to integument
(Skin = epidermis & dermis)
(Mucosae = surface membrane and CT support)
Mucosae
Functions
Protection (similar to physical barrier)
Communicative (may be sensory, may produce secretions)
Can be specialized in other ways (absorption, digestion)
Defense (like gut associated lymphoid tissue)
Mucosae
Components
Mucosal Membrane
Lamina Propria
Mucosal membrane
Component of mucosae
Epithelium, varied specialization
Lamina Propria
Component of mucosae Connective tissue support Loose CT Provides blood supply to surface membrane May overlie deeper CT
Sinus
Can refer to various components, can be:
Pockets within bones
Also depressions in dura to allow blood flow
Spaces
