Week 3 Module 2 Flashcards
1
Q
What is the organisation of the body?
A
Atoms - molecules - cells - tissues - organs - organ structures.
2
Q
What are tissues formed from?
A
Cells that originate from distinct regions of the embryo -> germ layers
- Germ layers dictate what tissue will form.
3
Q
How does organisation work?
A
Cells with specialised functions aggregate to form tissues with one or two specific functions. Specialised tissue comes together to form an organ. Several related organs form an organ system. Communicating organ systems make an organism.
4
Q
What do organs and systems help with?
A
Homeostasis. They also have rles in protection, support, and/or communication.
5
Q
What are the 4 different tissue types?
A
- Epithelial tissue - lines external and internal structures. eg. skin.
- Connective tissue - Acts as support and cushions all structures.
- Muscle tissue - 3 types: skeletal, cardiac, and smooth.
- Nervous tissue.
They are classified by function and structure.
6
Q
What are the functions of epithelial tissue?
A
A protective layer and a barrier between two environments. Controls the transport of substances into and out of the internal environment. They have the ability to excrete and absorb.
7
Q
What are epithelial tissues like cell wise?
A
They are densely packed with cells - highly cellular.
Under a microscope, it looks like aggregates of cells building a wall with little intercellular substances between them.
8
Q
Epithelial tissues are avascular. Explain
A
They lack their own blood supply, instead relying on surrounding connective tissue for nutrients.
9
Q
Are epithelial tissues polar or non polar?
A
They are polar (have 2 surfaces)
10
Q
What does the bottom surface of epithelial tissue do?
A
Connects to the underlying connective tissue though the basement membrane. This is important for survival since they are avascular.
11
Q
What does the Basement Membrane of epithelial tissue do?
A
Acts as a glue connecting epithelial tissue to connective tissue. Vital for survival as it allows exchange for nutrients and waste products.
Acts as a border for tissue regions
12
Q
What is the nature of the basement membrane?
A
It is semi-porous in nature, and is semipermeable.
Does not allow the transport of large molecules.
13
Q
What is the structure of the basement membrane?
A
Thin, only 20-100nm thick. Made up of proteins and proteoglycans.
Composed of 2 layers: Basal lamina and reticular lamina.
An interphase between the two tissues to support, nourish, and protect the epithelium.
14
Q
How does the classification of epthelia work?
A
Based on the number of layers and the cell shape .
1 layer is simple while >1 is stratified.
Flat is squamous, cubelike is cuboidal, long is columnar.
15
Q
What is simple squamous epithelium?
A
A single layer of flattened cells. Not very protective but allows for quick transport acoss the membrane. Found in lungs & blood vessels. (secretes lubricating substances).
16
Q
What is simple cuboidal epithelium?
A
Cube shaped cells. Form glands and have a secretory function, making molecules that can be secreted out the cell. Also absorb. Seen in kidney tubules.
17
Q
What is simple columnar epithelium?
A
Single layer of tall cells, shape suggesting there is a lot of space for organelles. This makes it good for absorbtion Found in gastrointestinal tract and small intestine.
18
Q
What is pseudostratified columnar epithelium?
A
Found in respiratory epithelium. Only appear stratified but are actually only one layer with nuclei found in different areas.
19
Q
What is stratified squamous epithelium?
A
Protective. Lines internal structures and forms skin in a specialised way.
20
Q
What is stratified cuboidal epithelium?
A
Not prevalent. Forms some glandular structures and has a protective role.
21
Q
What is stratified columnar epithelium?
A
Not prevalent. Lines some parts of reprofuctive systems. Secretes and protects.
22
Q
What is transitional epithelium
A
Specific to structures within renal/urinary systems. Allows the organs to expand or stretch.
23
Q
What are the types of epithelial tissue?
A
Surface epithelium that line the inside and outside surfaces of the body.
Glandular epithelium that forms exocrine glands. a.k.a. is used for secretion.
24
Q
List some epitheliums (?)
A
Endothelium, mesothelium, simple, stratified, respiratory epithelium, transitional epithelium.
25
Explain the epithelium - simple squamous epithelium.
Thin and smooth on the inside. Found in the cardiovascular and blood vessel lining. Allows continuous flow and exchange.
26
Explain the mesothelium - simple squamous epithelium.
Also a single layer of really thin cells, but has a thicker layer of underlying connective tissue.
Has a lubricative property and lines organs, being found in the pleura and peritoneum. (in lungs)
27
Explain simple cuboidal epithelium.
The nuclei are very large & centrally located + spherical. square shaped.
Can absorb but mostly make substances and secrete them to the extrecellular env.
Found in kidney tubules, small ducts in salivary glands, and in the liver.
28
Explain simple columnar epithelium.
Tall cells in a single layer. (contain microvilli for surface area). Major in absorption.
Found in gastro-intestinal tract. Surface faces the lumen where it absorbs and processes nutrients before passing it on to the underlying connective tissue to enter the blood tissue.
29
Explain stratified squamous (non-keratinized)
Many layers - have a protective role. They have a moist surface.
Found in the mouth and oesophagus, stratified to deal with mechanical abrasions.
30
Explain stratified squamous (keratinized)
Many layers with a protective role, but with a layer of dead cells on top.
These cells don't contain nuclei, but do contain a lot of keratin.
Form a protective and somewaht impermeable layer (eg. skin).
31
What is the other name for respiratory epithelium?
Pseudostratified columnar ciliated epithelium with goblet cells.
32
What does pseudostatified mean?
Appears statified but is only a single layer.
The nuclei are present on different levels.
33
What do respiratory epithelium contain and where are they found?
Contain goblet (mucus secreting) cells, and are found in respiratory tract for air filtration.
34
What do respiratory epithelium do?
Form a mucociliary-escalator, has a layer of mucus that traps dust, dead skin, etc.
Cilia on the top of the cells move the mucus up and out to either cough up or swallow.
35
What is transitional epithelium?
Epithelium that can change shape depending on function: stretched - squamous,
relaxed - cuboidal. Found in ureters and bladder. (needs to expand and contract)
Acts as an osmotic barrier.
36
How can you more simply refer to Glandular Epithelium?
Glands. They deal with secretions.
37
What are the two types of glands?
Endocrine and exocrine glands.
38
Explain endocrine glands.
Release secretions when it is hormones into the bloodstream to reach other parts of the body.
They form a part of the endocrine system.
39
Explain exocrine glands.
Release their secretions directly on tsurface of external linings of the lumina of our internal ducts to be imported elsewhere (eg. the surface).
40
Can exocrine glands be unicellular or multicellular?
Both. They can be unicellular (goblet cells) or multicellular (sweat glands).
41
What are the different multicellular glands based on the number of ducts?
One long straight duct is simple, while branches are compound.
42
How are multicellular glands classified based on the cluster of secretory cells?
Can be tubular: glands are shaped like a tube
Acinar: glands are berry/sac shaped.
Can be both - a tubular acinar gland.
43
How are glands classified by secretion type?
Serous glands secrete watery solutions that evaporate onto the skin to regulate body temp (eg. sweat).
Mucous glands produce a viscus mucous secretion that is protective by trapping dust and bacteria before they reach lungs.
Mixed glands do a combination of both (eg. saliva glands).
44
How are glands classified by secretion method?
Merocrine, apocrine, and holocrine.
45
How does merocrine secretion work?
The product is released from secretory vesicles via exocytosis. (most do this)
46
How does apocrine secretion work?
A portion of the cytoplasm containing the secretion is released. (breastmilk production). Made in the cytoplasm, aggregates near apical surface of cell and the membrane buds off forming a type of large vesicle.
47
How does holocrine secretion work?
The entire cell bursts to release secretion, killing the cell. (eg. sebacious glands that release oil in the skin).
48
Compare surface epithelium to glandular epithelium.
Surface epithelium refers to epithelia that cover both internal and external surfaces in the body, acting protectively.
Glandular epithelium are cells that secrete certain substances.
49
What is a secretion?
Fluid with either oil or proteins. eg. sweat, milk, mucous.
50
Unicellular vs multicellular glandular epithelium.
Sometimes we have single epithelial cells within epithelial layers that produce a secretion (eg goblet cells). At surfaces with greater demands for secretin, the cells aggregate forming a gland with infolding into the underlying layer of tissue. Connective tissue then forms around the gland.
51
What is an exocrine gland?
Secretions get secreted onto the lumen of an organ (eg. gastric glands) or are secreted onto the free surface of the epithelium (eg. the skin)
52
What is an endocrine gland?
They grow around blood vessels as the vessels are vital to transportation of secretions.
The secretions are mainly hormones. The hormones enter the blood stream and are transported to the target cell.
Exo is local/short time. Endo is long distance/long acting.
53
What are simple glands?
Glands with a single duct that is shared by all the cells in the gland to excrete the substance out.
54
What are the different types of simple glands?
Simple tubular, simple coiled tubular, simple branched tubular, simple alveolar (acinar), simple branched alveolar.
55
What are compound glands?
Glands where the duct is not shared between all glands.
56
What are the different types of compound glands?
Compound tubular, compound alveolar, compound tubuloalveolar.
57
How are epithelial cells joined together due to their protective wall with little intracellular space between them?
Tight junctions, adherant junctions, desmosomes, gap junctions, hemidesmosomes.
58
What is the common feature between all cell junctions?
They involve the plasma membrane of one cell structurally binding to the membrane of the next door cell.
59
Explain tight junction structure.
Firmly adhere adjacent cells. Seal cells together by fusing the plasma membrane, forming an impenetrable barrier. Generally placed apically, or close to the surface of the cell, can be found in intestine epithelium.
60
Explain adherant junction structure.
Form a continuous adhesion belt just below the tight junctions. Formed by intracellular anchoring proteins, part of the cytoskeleton. Bind protein filaments located in the cells plasma membrane. They encircle each of the interacting cells, joining them into a sheet.
61
Explain the function of tight junctions.
Forms a seal that prevents molecules passing the two cells. Anything coming from the lumonous side has to cross the membrane.
62
Explain the function of adherent junctions.
The junction connects deep inside the cell, connecting the tension bearing filaments of the cytoskeleton. They tightly hold eachothers internal scaffolds, allowing them to withstand large forced. Widely distributed, mainly found in areas with severe mechanical stress (eg. the heart).
63
Explain the structure of desmosomes.
Formed under/next to tight junctions, they are interlocking proteins. Inside the cell, they serve as anchoring sites for rope-like filaments - forming a structural network of great tensile strength.
64
Explain the function of desmosomes.
Firmly adhere and strengthen the bonds between 2 cell. Through desmosomes, the protein filaments of adjacent cells are linked into a net throughout the tissue.
Found between epithelial cells that need to withstand stress (eg. skin)
65
Explain gap junctions.
Communicating cell junctions - allows passage and exhange of small ions and molecules. Made of channel forming proteins. Allow ions to move from cytoplasm of one cell to another, coupling internal environments electrically and metabolically.
Allows messages to pass between cells, allowing functions to be coordinated.
66
Explain hemidesmosomes.
Specialised anchoring junctions that serve to connect the basal surface of an epithelial tissue to underlying basement membrane.
Resemble desmosomes morphologically and structurally, distributing tensile/shearing forces through an epithelium.
67
In what cell type are cell junctions not present?
Blood cells.
68
What are some examples of cell stressors?
When cells lack nutrients, have chemical/viral invasions, mechanical abrasions, injuries, mutations (cancer).
69
How do cells adapt to stress and how do they decide?
Cells decide on a specific response based on multiple factors: if the cell can divide, type of stimulus, duration and seversity, and how well the cell can overcome the conditions.
-Change in appearance (generally changes function) until they overcome it or undergo apoptosis or grow out of control.
- name end trophy = change in size
- name end plasia = change in number
70
What is atrophy?
A decrease in cell size/shrinkage of an organ.
Often occurs due to lack of nutrition. It needs to conserve energy and thus eliminates organelles from the cell, undergoes apoptosis.
71
What is an example of atrophy?
Muscle atrophy is common for individuals that have had injuries or in old age where the muscle cells aren't used and undergo atrophy.
72
What is hypertrophy?
Increase in cell size. When tissues are continuously stimulated and there is an increase in the blood supply in the area. Generally includes an increase in protein content.
73
What is an example of hypertrophy?
Bulking up. Muscle cells divide and thus increase in size to withstand mechanical stress.
74
What is hyperplasia?
Increase in cell number / growth which increases tissue size. May be physiological or pathological.
Seen in responding to chronic inflammatory state.
75
What is metaplasia?
When a differentiated cell transforms into a different cell type.
Usually happens when cell encounters a stress it can't handle (eg. smoking), changing to withstand it.
Can do back if stressor is removed.
76
What is dysplasia?
Similar to metaplasia, but changes into a premature state. - Seen as a pre-cancerous stage. At this stage, cells become disorganised, losing cell to cell contact, their structure and function, becoming precancerous. Lose sense of border (of tissue).
The immature cells aren't able to withstand the required functions of the tissue.
77
What is neoplasia?
New formation / development <-cancer cell. Accumulates so many mutations that it doesn't obey control signals and thus grows out of control without undergoing cell death. Leads to organ failure when hyperplasia takes over. Once neoplasia has been reached, the damage is irreversible.
78
What are the two types of neoplasia?
- Benign: Localised in one area (not harmful, can be stopped)
- Malignant: Lost any sense of borders and invades other tissues.
79
How does a normal cell develop into cancer?
Normal -> Hyperplasia -> Dysplasia -> Cancer.
First cells start growing in number, then they lose cell to cell contact and become disorganised, then lose sense of border of tissue and invade other tissues. Loses controll and will not undergo cell death or stop dividing.
80
What is the end stage to chronic stress on cells?
Cancer.
81
What are the four types of tissue?
Epithelial, connective, muscle, and nervous tissue.
82
What is the distinguishing functional feature of connective tissue?
To serve as support and protection. As a result they must be tensile and strong.
83
What must connective tissue be to connect and bind organs together?
Tough and flexible.
84
What do connective tissue do?
Form a network of communication allowing for synchronised reactions. - maintains homeostasis.
85
What is the structure of connective tissue?
Made up of cells - few but many types. Extracellular matrix is made up of 2 components; brown viscus fluid component and fibres (collagen, elastic, and reticular)
86
What is the main defining feature of connective tissue that defines the type of connective tissue?
The Extracellular matrix.
87
Explain connective tissue classification.
Based on structure that defines function. The 3 types of connective tissue:
- Connective tissue proper
- Fluid connective tissue
- Supporting connective tissue.
88
What is connective tissue proper?
Contains lose and dense tissue that cushions and lines internal structures.
89
What are the functions of connective tissue?
Provides mechanical support and protection, houses and protects vital organs.
Acts as an insulator, regulator and sensory organ.
90
An example of connective tissue coming in clutch?
Epithelia form top layers of skin, coming with underlying connective tissue that fulfills these roles.
91
How does connective tissue act as an insulator?
Fat acts as an insulator, found around organs and tissues. Provides role of cushioning and protecting.
92
How does connective tissue act as storage?
Fat is a great storage of energy.
93
How does connective tissue act as defence?
Connective tissue in blood/lymph are where immunity involved cells travel to locations that need immune reactions.
94
How does connective tissue act as repair?
Skin regenerates after a cut, epithelium is avascular thus connective tissue brings required substances and nutrients. Also happens in internal organs and tissues.
95
How does connective tissue act as communication and transport?
Found all aroud organs gluing them together. Allows transport of messenger molecules and other molecules. Allows exchange of nutrients, gases, and waste products.
96
What are the two types of connective tissue proper?
Loose and dense. Based on structure.
Constituents: ground substance (fibres + cells) and fibres (cells + AGS)
If CT proper is mostly ground substance, it is loose. Mainly fibres and it is dense.
97
What is dense regular connective tissue?
If fibres are parrallel to one another
Found in ligaments (bone to bone) and tendones (muscle to bone)
Allows transmission of force from muscle to bone. Form a muscular skeletal system - facilitate role of structure and movement.
Tensile/strong but only works in one direction.
98
What is dense irregular connective tissue?
If fibres are not parrallel to one another.
Irregular makes it good for cushioning, making it line internal structures.
Can withstand force from many directions due to stucture.
Located under epithelium of the skin, around liver, spleen, and other organs, and around bones (sheath).
99
What is loose connective tissue?
High content of ground substance - high in nutrients for other cells. Allows immune cells to travel easily to fight infections. Perfect passage way for nerves and blood vessels that travel to distinct parts of the body.
100
Where is loose connective tissue found?
Underlining epithelia, blood vessels, srroudning muscles, and forming an outer lining for heart and lungs and pericardial sacs.
101
What are the connective tissue constituents of cell types and ground substance fibres?
Cell types: Macrophage, fibroblast, lymphocytes, far cells, mast cells, and neutrophils.
Ground substance fibres: Collagen, elastic, and reticular fibres.
102
What is ground substance?
What surrounds everything extracellularly. Provides structural and biochemical (nourishment) support that's required for cells to survive and secrete the fibres. Allows us to live.
103
What are the functions of ground substance?
Controls/regulates communication, regulating transport of substances through it. I.e. messenger molecules, hormones, neurotransmitters. Allows communication through cells and long distance communication of organs and tissues. Allows exchange of nutrients and waste.
104
What is the structure of ground substance?
Amorphous (without a shape), clear, colourless, viscous fluid. Secreted mainly by fibroblasts, mostly made up of water but contains glycans (carbohydrate), and proteins.
105
How can ground substance vary?
In viscosity that regulates ability of substance penetration. High viscosity can be a line of defence, preventing bacteria and microbes from getting to vitals.
106
What is oedema?
Swelling. Seen when bruised, due to accumulation of fluid in ground substance - inflammation clears up - swelling goes away.
107
What are collagen fibres?
Most abundant fibre, main component of structure in connective tissue. Strong - allows a lot of strength and tensile force, but also cushioning supportwen organs are protected by CT. Found in cartilage, bone, tendon, ligaments abundantly, but amount and arrangement varies accross different tissue types.
108
What are elastic fibres?
Made from elastin - not as strong as collagen but allows relaxation, stretching, and recoil of fibre - provides flexability which is vital for organ support. Elastin diminishes with age - leads to sagging of skin. Seen in skin, arteries, and bronchi.
109
What are reticular fibres?
Made up of reticulum. Similar in structure to collagen but finer. Not as strong but allows formation of a really fine network/framwork that provides a scaffold for very specific tissues. Handy to complex tissue archetecture. Eg. spleen, liver, marrow - holds segments and features of these in place. Not elastic.
110
What are the structural and storage connetive tissue cells?
Fibroblasts and fat cells (adipocytes).
111
Whare are the defence connective tissue cells?
Cells of the immune system. They travel through fluid connective tissue then loose connective tissue to travel to necessary areas.
112
What are reserve connective tissue cells?
Stem cells that sit inside connective tissue and wait to recieve signal of damage, etc. Turn on, proliferate, mature, repair and regeneration mechanism, helping structures around them.
113
What are fibroblasts?
Main cell present in CT. Very metabolically active, constantly secreting and producing proteins. Make the proteins of the ground substance and fibres. Look spindle shaped and have fibrastic processes moving away from the centre of the cell.
114
What do fibroblasts do?
Act quickly when tissues/organs are damaged -> activate to proliferate (grow in number) and to secrete abundant amounts (generally collagen) to form scar tissue. Seal and heal damaged area, no further threat.
115
What are adipocytes?
Fat cells- reserves of energy. When aggregated, act as good insulation, shock absoption, and protective padding. Particularly cushion soles of feet and also around organs. In obesity, increase of size of adipocytes, not number. Hypertrophy not hyperplasia.
116
What are white and brown fat?
White: Adults mostly have. Stores of energy.
Brown: cells contain many mitochondria. Babies have many. Involved in thermoregulation.
117
What are Leukocytes?
White blood cells, made in bone marrow, circulate fluid connective tissue and exit to enter the extracellular matrix. Include: Lymphocytes, neutrophils, and eosinophils.
118
What are lymphocytes?
A part of most immune responses: innate reactions, adaptive.
119
What are Neutrophils?
Present in inflammatory reactions and bacterial infections that cause inflammation.
120
What are Eosinophils?
Present in less responses - parasitic and allergic reactions.
121
What are macrophages?
Quite big cells of the immune system, derived from monocytes (leukocyte) - another type of white blood cell. Known as phagocytes. Once activated, they engulf a particle through phagocytosis if it has been labelled threatening.
122
What do macrophages digest and why?
Microbes, dying cell, cancer, cellular debree, etc.
Digest and process the particles, remove debree, and ensure no threat it present.
123
What is the role of macrophages in lungs and spleen?
In lungs they are 'dust cells' and ingest dust that made it into the lungs.
In spleen, they are 'RBC scavangers' as spleen is the place red blood cells go to die - Sometimes they recyvle RBC components.
124
What are Plama cells?
Immune system, originate from lymphocytes.
When activated, they secrete antibody cells.
Each different antigen will have a different antibody made to it (if thats how the specific threat is neutralised.
125
What are Mast cells?
Involved in inflammatory response, they release histamines in response to allergic reactions. Histamines stimulate vasodilation, stimulate mucus secretion, contraction of smooth muscle (difficulty breathing).
126
What is the integument?
Considers the skin and is our support structure (made of epithelium and connective tissue).
127
What are the roles of the skin?
Protects - acts as barrier to external environment.
Immunity - first line of defence against infection
Largest sensory organ - pressure, temp, pain, helping body react accordingly.
Thermo regulation - Allows core temp to be regulated irrespective of external.
Water balance and waste excretion of urea, uric acid, ammonium. (metabolic)
Vit D production - hormone fundamental to biochemical reactions, mainly in healthy muscularskeletal systems. In skin, vit D is not active but reactions with UB light.
128
What are the 3 layers of the skin?
Main 3 layers:
- Epidermis: top most superficial layer - what is seen when looking at the skin.
- Dermis: epidermis is an epithelial layer, therfore dermis is underlying connective tissue that supports it.
- Hypodermis: a layer of adipose tissue.
129
What is the epidermis?
An epithelial layer made of stratified squamous keratinised epithelium. Many layers with the top being flattened. Contains keratinocytes that can secrete keratin. Avascular, relying on the underlying connective tissue for nourishment.
130
What makes epidermis specialised?
It is keratinised - top layer is covered in keratin which gives skin its protective function.
131
What is the epidermis connected to?
The dermis through a semipermeable basement layer.
132
What is the predominant cell type in the epidermis?
The keratinocyte.
133
What do the epidermis layers correspond to?
Different phases or keratinocyte maturation, thus different phases and stages of function.
All layers have stratum at the front of the name, meaning layer. Most are named off appearance with basal as exception as it is the bottom layer.
134
What is the stratum basal(e) (aka. stratum germinativum - germinating layer)?
Germinating layer wheere keratinocytes begin to grow, provides other layers with necessary cells. Continuous reproduction and division of cells.
Made up of columnar cells. Basal keratinocyte - stem cells.
The layer that forms epidermis connection with basement membrane and CT.
135
What does stratum basal do?
Ensures all above layers are produced and maintained.
136
What is the stratum spinosum?
Cell layer with cells that have spiny projections connecting them to other cells.
Makes up a lot of epidermous. Cells constantly undergoing sheering mechanical forces, cell junctions (aesmosomes and adhesion) play a vital role in maintaining structural integrity. The spikes are the proteins of the desmosomes.
137
What does the stratum spinosum do?
Ensures protection of stratum basal - provides resiliance and strength.
138
What is the stratum granulosum?
Thin granular layer. Keratin production 3 layers in has reached a point where they are accumulated into granules - can be visualised under light microscopy.
Granules have loaded up cytoplasm and are moved into extracellular space (secreting the keratin)
139
What is the stratum lucidum?
Thin, clear layer not present in thin skin (eg. only on palms and heels). The cells are starting to die and are filled with an intermediate form of keratin. Seen under microscope as a thin clear line - eleidin is clear.
140
What is the stratum corneum?
Layer of keratin. Cells from bottom have now secreted large amounts of keratin into their cytoplasm which moves extracellularly. At this point, cells are embedded in the keratin. Can no longer divide or undergo the cell cycle: no nuclei or organelles present. Prone to shedding after scratches and daily life - replaced often. Thick.
141
What is different about the cells at the stratum corneum?
No longer alive or dunctional. Present a water resistant layer, protecting lower layers of epidermis and body from threats.
142
What is keratinisation?
Making of keratin protein and secreting it.
143
What is keratinisation like at the basal layer?
Keratinocytes are focused on dividing to ensure there is enough supply for further layers. Keratin production starts but is not the focus.
144
What happens to keratinisation as cell moves toward surface?
Production increases. At stratum granulosum, cells begin to flatten out, and in granuoles keratin seeps into the extracellular space. Nuclei also disappear.
145
What happens to keratinisation at the stratum corneum?
Layer of keratin where dead cells sit embedded. Important layer, acting as a seal ensuring protection of lower layers.
146
How long does it take for keratinisation to occur?
Around 28 days. Epidermal regenerates in that period. (less for younger people).
147
Compare thin skin and thick skin.
Thin skin: covers most of the body. Thin epidermis and corneum. No stratum lucidum.
Thick skin: On palms and heels. Much more protected (enlarged layer of keratin). Real thick is important for bare feet. Does not contain hair follicles. Yes stratum lucidum.
148
What are the 4 cell types of the epidermis?
Keratinocytes, langerhans cells, merkel cells, and melanocytes.
149
What are keratinocytes?
Most cells in epidermis, produces keratin, thus provides superficial layer its protective quality. Allows regeneration and is the building block/structural epithelial cell.
150
What are langerhans cells?
They monitor and connect with surrounding cells. Cells of the immune system, dendritic (antigen presenting) cell. 'patrol system' that informs immune system. Made in bone marrow and moved through blood as a monocyte until differentiating into langerhans cells that live in the epidermis (mainly stratum spinosum).
151
What is the function of langerhans cells?
They look for potential invading pathogens. When this happens, it ingests the threat, taking it away from the skin to a checkpoint in the system - in skin it is a lymph node.
Once it phagocytosed and digested it, it can pick out antigens (marking proteins) which are given to the immune system allowing them to recognise it and choose to react locally/systematically, or not if there is not danger.
152
What are melanocytes?
Cells that produce the pigment melanin. They live inthe epidermis surrounded by keratinocytes in the stratum basal. Melanocytes have an octopuslike structure with a cytoplasm that extents into the extracellular space, surrounding keratinocytes. More sun exposure - more melanogenesis.
153
What do melanocytes do?
Produce and secrete melanin, packages it into melanosomes (specialised vesicles). The melanin is ingested by surrounding keratinocytes in endocytosis, making it a part of the cytoplasm. Melanin moves to the surface of the cell, positioning itself across the surface. This protects DNA from UV light exposure.
154
What are merkal cells?
Connection between skin (sensory organ) and nervous system. Mechano receptors - can detect changes in pressure, respond to stretch. Reside in the basale but communicate with cells around them and integrate with that space. Convery into to the nervous system cells that report to control mechanisms to decide how to respond.
155
How does naming around the dermis work?
Epi - (above). Hypo - (below).
156
What joins the epidermis to the dermis?
A corrugated surface (meandering joining line). This allows extra surface area, adding strength to the bond.
157
Why is a corrugated surface between epidermis and dermis important?
Epithelium requires CT, cannot survive if junction is compromised. Dermis likewise cannot survive without protection.
Epidermal ridges that extend into dermis create finger prints.
158
What do dermal papilla do?
Rise up into epidermis.
159
What are the two layers of the dermis?
Papillary dermis and reticular dermis.
160
What is the papillary dermis?
Made of loose connective tissue - abundant in ground molecules allowing movement of molecules, allowing blood vessels to travel, and housing nerves. Allows for nourishment of epithelial layer and exchange of gases and wastes. Allows communication. Support epithelium/support the hypodermis.
161
What is the reticular dermis?
Dense connective tissue, thick collagen fibres. Provides structural support to protect underlying tissue from mechanical forces. Support epithelium/support the hypodermis.
162
What is the hypodermis?
Sits underneath the dermis, mainly composed of aggregated adipocytes (fat cells). Stores energy and cushions. Hypodermis with its location is vital to insulation - prevents heatloss. Protects from further mechanical damage, protecting vitals underneath everything.
163
What do ancillary structures do?
Together with cell layers form integument, helping skin perform all its functions.
164
What do nerves need to do in the skin?
Need ability to perceive changes and threats to report to the nervous system to react accordingly. Nerve endings present throughout skin in the dermis - detects temp, touch, pain, pressure.
Distribution varies - High in places like hands/fingertips.
165
What are the two types of sweat glands?
- Merocrine (eccrine): widely distributed. Secrete directly to skin surface.
- Apocrine: restricted to underarms. Connected to hair follicles/restricted in use. Rely on hair shaft.
166
What controls sweat gland secretions?
The autonomic nervous system. As such it is involuntary. Involved in thermoregulation.
167
What is the structure of sweat glands?
Secretory portion - epithelial cells sit, making swear and releasing it.
Duct pertion - tunner swear travels through.
168
What is the function of sweat glands?
Thermoregulation - controls temp.
Waste removal - wastes build up from metabolic processes.
169
How are hair and hair follicles related to sweat glands etc?
Involved in sensation and thermoregulation.
Most follicles are associated with a sebaceous gland. (sits to both sides, making and secreting sebum).
Arrector pilli muscles.
170
What happens in thermoregulation when it is cold?
Blood vessels in dermis constrict, lumen gets smaller and less blood flows through the space. Blood insteead flows deeper and to vitals. Arrector pilli muscles contract making hair erect. Traps heat through air molecules.
171
What happens in thermoregulation when it is hot?
Hermal blood vessels dilate. More blood flows close to epithelium, allowing heat to be released. Sweat glands produce sweat leading to evaporation. Arrector pilli muscles remain relaxed so air can remove heat from skin.
