Exam 3 Flashcards Tissue Bio

How much % of body mass does skin account for

15-20%

What are 5 functions of skin

1. Sensory - Through receptors

2. Homeostasis - ex: temperature regulation (sweat/evaporative cooling)

3. Protection - immune and environmental defense/barrier

4. Secretion - Through glands

5. Others like calcium metabolism and attraction between sexes

How many layers of skin are there? Name them in order from surface layer

At the surface is the epidermis and then underneath it is the dermis, then there is the subcutaneous/hypodermis layer

What kind of tissue is the Epidermis?

Keratinized stratified squamous epithelium

What kind of tissue is the Dermis?

Connective Tissue

What are some components found in the Dermis?

Hair follicles, glands, blood vessels, lymph vessels, sensory receptors, muscles and neurons

How many layers does the Dermis have? Name and locate in order from the surface

2, the papillary directly under the epidermis and reticular layer underneath the papillary and above the subcutaneous

What are some of the characteristics of the Papillary Layer?

Has a thin dermal papillae

Classified as loose connective tissue with randomly woven fibers, and contains elastic fiber.

Also is “folded” in appearance

What are some characteristics of the Reticular Layer?

Composed of dense CT

larger/thicker than the papillary layer

Made of collagen and elastic fibers. It is not randomly woven, made of parallel lines called Langer’s Lines. In surgery, it is important to cut between the fibers.

What are some characteristics of the hypodermis/subcutaneous

Mostly made of white fat (AKA subcutaneous fat)

It is caloric intake dependent

Useful in energy storage and insulation

How are the layers of the epidermis classified? Name them in order from the surface (Not including stratum disjunctum)

Classified/organized based on structure and function

1. Stratum corneum

2. Stratum lucidum

3. Stratum granulosum

4. Stratum spinosum

5. Stratum basale/germinativum

What is the Malpighian layer?

The stratum basale and spinosum

What are some characteristics of the stratum basale?

Base/bottom of the epidermis, serves as the germ layer and cell division is often found in this layer. Single layer of cells are not uniform in shape and are normally cuboidal or columnar

What are some characteristics of the stratum spinosum?

Cells have a prickly/spine like appearance, with a halo of intracellular space. Cells are bound together at the tips of these spines in the intracellular space by bundled desmosomes

What is a Node of Bizzozero?

The bundles of desmosomes at the tips of the spines in the intracellular space of the stratum spinosum

What are some characteristics of the stratum granulosum?

The layer is basophilic, about 2-4 cells thick, and contain keratohyalin granules, which marks the start of keratin formation

How is keratin formed? Where?

Formed in a reaction between cytokeratin and keratohyalin, starting at the stratum granulosum.

As it progresses towards the surface, the keratohyalin granules increase in amount and size

What are some characteristics of the stratum lucidum

Cell layer is thinner and flatter. Cells themselves are transparent and acidophilic, have no nucleus, and contain eleidin.

They are only found in certain skin regions (thick skin)

What is eleidin? Where is it found?

Eleidin causes the acidophilicity in the stratum lucidum and is an intermediate leading to keratin.

What is the difference between thick and thin skin?

Thick skin has a stratum lucidum and is found in the palms, soles, and fingertips.

It refers to the thickness of the epidermis not the entirety of the skin.

Thin skin is the rest of the body’s skin, and the thickest skin overall is the nape

What are some characteristics of the stratum corneum?

The surface layer of the epidermis, contains dead cells and has keratin. It varies in thick skin and is thickest in areas of friction. The friction areas form a barrier called the callus

Name some of the cells of the Epidermis

Keratinocyte, melanocyte, Langerhans cells, and Merkel cells

Where can keratinocytes commonly be found?

Commonly found in the stratum basale, spinosum, and granulosum

What do keratinocytes do in the stratum granulosum?

make keratohyalin granules and lamellar bodies

What do keratinocytes do in the stratum spinosum?

They continue keratin production, where filaggrin-bundled tonofilaments become tonofibrils. Those fibrils insert into desmosomes and hemidesmosomes. Ultimately helps functions such as countering friction

What do keratinocytes do in the stratum basale?

When active, they play a role in cell division and because of their abundant ribosomes (dark staining), also play a role in production of cytokeratin tonofilaments

What are other activities keratinocytes can do

nonsoluble loricrin and involucrin into the membrane, leading to the barrier of inside vs outside

movement of keratinocytes to the surface causes serine protease activation, leading to formation of desmosomal proteins and thickness maintenance of the corneum

What are lamellar bodies in skin?

AKA Odland bodies or membrane coating granules (MCG), they are small (.1-.5micrometer) membrane bound organelles with lipid layers called lamellae which secrete into the intracellular spaces

What are Keratohyalin Granules (KG)?

1-5micrometer non membrane bound, non secreting inclusions that are composed of filaggrin, and the basophilic-character-producing phosphate rich proteins and RNA.

What do KG do to impact the stratum lucidum?

React with tonofilaments by sucking them in to form eleidin in the stratum lucidum, leading to the layers acidophilic, lucid nature.

What are desmosomes? What are hemidesmosomes?

Desmosomes are complexes that bind cells together (think of Nodes of Bizzozero), hemidesmosomes bind the dermis and epidermis

What are Melanocytes?

Cells that produce melanin in membrane bound melanosomes, 3rd most common in the epidermis (~5% total)

Found at the stratum basale’s basement layer (basement membrane between dermis and epidermis)

There are no junctions between cells

They vary in location and are not uniform throughout the skin, and more sun exposure doesn’t always correlate to more melanocytes. Also contribute to attraction between sexes

What is the origin of Melanocytes?

They come from the ectoderm, specifically a bunch of cells called the neural crest

What are the stages of melanin production?

1. Stage 1 melanosome - Golgi makes a .25 micrometer secretory vesicle containing the tyrosinase (an enzyme) and proteins

2. Stage 2 Melanosome - Proteins arrange in a grid with periodicity, laying down the framework for where melanin is deposited

3. Stage 3 Melanosome - Tyrosine is transformed into Dopamine, then melanin

4. Stage 4 Melanosome AKA Mature Melanosome - Full of melanin, the enzyme stops by cytocrine secretion

Where can Langerhan’s (Epidermal Dendritic) Cells be found?

Reed/rete ridges in near/in the stratum spinosum

What is the origin of Langerhans Cells?

From bone marrow and the mesoderm, not the ectoderm

What are some characteristics of Langerhan’s Cells

Make up 3% of the cells in epidermis

Have Birbeck granules that are tennis racket shaped membranous inclusions in the cytoplasm, exclusive to this cell

Part of the Mononuclear Phagocyte System (MPS)

What are some of the functions of the Langerhan’s Cells?

1. Monitor the epidermis for passing antigens (Antigen presenting cells/APC). If encountered, they are phagoticized and displayed on the cell surface. Then they migrate to the lymph nodes

2. Play a role in the delayed-type hypersensitivity reaction. Commonly in contact dermatitis and allergies

What is the location and origin of Merkel (Epidermal Tactile) Cells?

Cells of epithelial/basal origin and are located in the stratum basale

Have cell processes similar to dendrites, extended between keratinocytes and attached by desmosomes

They have numerous dense-core neurosecretory vesicles (Less than 100 nanometers in size) which contain catecholamines

What are some of the functions of Merkel Cells?

Act as afferent (pseudo-unipolar/sensory) neurons, making it essentially a sensory receptor.

Form a light touch mechanoreceptor called the Merkel’s Corpuscle

What are some of the receptors in skin?

1. Free, nonencapsulated nerve endings that penetrate into stratum granulosum. Ex: Nociceptors, that are the most numerous pain receptors in the epidermis

2. Pacinian Corpuscle - encapsulated, deep in dermis near the hypodermis, leading to it being less sensitive than the free, nonencapsulated nerve endings

3. Meisner’s Corpuscle - encapsulated, located much shallower (In dermal papillae) and are more sensitive

How are the parts of the Respiratory system classified? What are the parts?

Based on how each part interacts with air, there is the Conducting Portion and Respiratory Portion

What is the Conducting Portion? Where is it located?

Part of the respiratory system mainly responsible for the passageway of air, spans from the nose to the terminal bronchioles in the lungs

What are some of the functions of the Conducting Portion?

1. Passageway of air

2. Condition Air

   1. Adjust humidity

   2. Remove Particulates by sticking to a wet surface

3. Sense of smell

4. Production of speech/verbal production

What is the Respiratory Portion? Location and Function

Part of the Respiratory System, spans from the respiratory bronchioles to the alveoli. It executes gas exchange

What are some parts of the Vestibule?

The Nasal Cavities (left and right) separated by the nasal septum

What are the parts of the nasal cavity?

The vestibule (nasal cavity) and the nasal fossa, which is larger and starts at the end of the vestibule

What is the function of the vestibule, and what is an important component of it?

It conditions air and contains vibrissa, which are short hairs that act as a coarse filter to catch larger particulates

What are the components of the nasal fossa, and their locations?

Turbinates/Conchae which lie on the lateral surfaces opposite the septum. Contain 3 bony shelf like projections called the superior, middle, and inferior concha.
Swell bodies/Venous Plexus is a system of blood vessels that form a branching network under the epithelia of bone surface

What is one of the function of the Conchae?

To condition air by increasing the surface area of boney surface that interacts with air, increasing efficiency and causing the air to swirl around the fossa

What prevents epithelia in the fossa from drying out? Which part completes this process?

Every 20-30 minutes, the venous plexus engorges one fossa in blood, causing swelling which pushes epithelia outwards and reduces the airspace. This results in the other fossa to take in more air in a 60/40 split. As one inflates, the other deflates.

How does blood flow in the Nasal fossa? What happens as a result and what component of the fossa conducts this?

The venous plexus is responsible for the distinct directional flow of blood, where larger vessels towards the back move blood to the front of the nasal cavities. This cools the blood (98.6F) and warms the air in the area, increasing efficiency.

What is the epithelium of the Vestibule?

Nonkeratinized stratified squamous epithelium. It’s a transition epithelium, since its part of the transformation from epithelia of the skin to respiratory epithelia.

What is the epithelia of most of the Nasal fossa?

Typical respiratory epithelium

What cells make up typical respiratory eptihelium?

1. Ciliated pseudostratified columnar cells

2. Goblet cells

3. Brush cells

4. Small granule Cells

5. Basal Cells

Why are Ciliated pseudostratified columnar cells important to respiratory epithelium?

Their cilia takes out mucous and other airway blockers

What is the function and commonality of goblet cells in respiratory epithelium?

2nd most abundant, function as columnar cells that produce mucous

What are brush cells? Function and cell type

Columnar cells that have blunt microvilli, form synapses on their basal side with afferent neurons of the trigeminal nerve (sensing generation sensation, causes sneezes)

What is the function of the basal cells of the respiratory epithelium

They are short Cells that line the Basement membrane, serve as stem cells for epithelium

What are the exceptions to typical respiratory epithelium? Name location and type of epithelia replacing it

1. Located in the superior turbinate and roof of the nasal fossa, the replacement is olfactory epithelium. Also contains a Bowman’s gland

2. Located in the larynx, specifically the epiglottis and vocal cords, the replacement is nonkeratinized stratified squamous epithelium

What are the different cell types of olfactory epithelium?

1. olfactory cells

2. sustentacular cells

3. basal cells

4. brush cells

What are olfactory cells? Where are they found?

They are found in olfactory epithelium. They function as afferent/sensory/bipolar neurons that have axons that penetrate the basement membrane into the connective tissue to form fibers of the olfactory nerve. The ends of their dendrites (which project to the apical surface) have non-motile cilia that contain odorants

What are odorants?

Chemicals that produce odor

What are sustentacular cells? Where can they be found?

They are the most numerous cell of the olfactory epithelium, have microvilli, they support olfactory cells physically, and use odorant binding proteins to support them metabolically

What is a Bowman’s gland?

They are simple serous acini that live underneath the olfactory epithelium embedded in Connective tissue called lamina propria

What is the function of a Bowman’s gland?

They secrete watery serous solution which

1. keeps the surface wet

2. Serves as a solvent for odorants

3. Cleans the surfaces due to it’s constant secretion.

What is the trachea? What are some characteristics?

Marks beginning of the respiratory tree, it spans about 10 inches from the junction of the larynx until the thorax (chest cavity). It’s a rigid tube held together by semi crescent shaped hyaline cartilage, and divides in two at the beginning of the primary bronchus. Lined with respiratory epithelium up until the bronchioles

What are some characteristics of the primary bronchus?

In the lungs, they split 9-12 times until they reach about 5mm diameter. When they result in a passageway that lacks cartilage, its called a bronchiole

What are small granule (Kulchitsky) cells

They are 100-300nm diameter cells of the Diffuse Neuro Endocrine System (DNES), and have dark staining secretory granules

What are the types of small granule cells in the lungs, and what is classification based on? What are their functions?

Based on granule composition, and both function as local effectors of cell function or in other words Paracrine Hormones. There are two types of these cells

1. Catecholamines, part of the Amine Precursor Uptake and Decarboxylation (APUD) subgroup of the DNES

2. Other chemical categories like serotonin and larger molecules like peptides and hormones

What are some features of the Terminal Bronchioles’ epithelium and lamina propria?

1. They have ciliated simple columnar epithelium instead of pseudostratified, meaning they are shorter in height

2. Feature Club cells (Bronchiolar Exocrine cell)

3. Normally don’t have Goblet cells

4. Smooth muscle presence in the lamina propria

What are Club Cells?

Dome shaped, non ciliated cells that secrete:

1. Surface-active agent

2. Club Cell secretory protein (CC16)

What is the Surface-active agent of club cells?

A lipoprotein that reduces surface tension and prevents collapse of airways

What is protein CC16 (Club cell secretory protein)

A protein that protects the lining of the lower respiratory system, regulates the inflammatory process, and has some uses as an antiviral protein in special cases

What is metaplastic change and a common cause for it?

Caused often by smoking, it involves the development of goblet cells in terminal bronchi due to irritation

What parts of the nervous system innervate the smooth muscle in the lamina propria of terminal bronchi?

Contracted by the vagus nerve (parasympathetic) and dilated by the sympathetic NS

What are Respiratory Bronchioles? What are their features?

They are after the end of the conducting portion and at the beginning of the respiratory portion. Its not a complete transition, and its lined the same as the terminal bronchioles

Where are Respiratory Bronchioles not lined the same as Terminal Bronchioles?

At the alveoli, where the pockets/expansions of airway surface exist

What are alveoli?

Lined with simple squamous epithelium, they are pockets/expansions of airway surface in the respiratory bronchiole, as progressed further down the airway, they become more abundant and are called alveolar ducts. Eventually at the end they are clustered and called alveolar sacs

What cells make up the alveoli’s epithelium?

1. Type I pneumocyte (Squamous alveolar cell) - make up 97% of the alveolar surface and are thin and attenuated with a thin cytoplasm

2. Type II pneumocyte (Great alveolar cell) - make up about 3% of the surface, and are dome shaped with lamellar bodies AKA secretory glands.

3. Brush cells

What is the composition and function of the lamellar bodies in Great Alveolar cells?

Made up of phospholipids, neutrolipids, and proteins, they secrete pulmonary surfactant.

What is pulmonary surfactant? Where does it come from?

Secreted from the Great Alveolar (type II pneumocyte) cells, they are a phospholipid that reduces surface tension and allows airways of alveoli to remain open

What is a dust cell?

An alveolar macrophage that removes particulates and sends them up the airway to be excreted