Histology Flashcards
(81 cards)
1
Q
Tissue
A
It is a collection of similar cells which act together to perform a particular function
E.g muscle tissue for movement, epithelial tissue for protection
2
Q
4 types of tissues
A
- Connective tissue
- Muscle tissue
- Epithelial tissues
- Nervous tissue
Connective - support
Muscle - Move
Epithelial- protect
Nervous - neurons
3
Q
Epithelial tissue
A
Function: protection/ protective coverings (skin/ mucus membrane)
- acts as protection against bacteria and a buffer against mechanical injury
- cells are closely packed together
- secretion and absorption
- lines the body’s surface both inside & out
- consists of cells held together by matrix
4
Q
Connective tissue
A
Supportive, protective, binding
Fats, ligaments, tendons, bones, cartilage and lymph and blood are all connective tissue structure
5
Q
Muscle tissue
A
Contracts and relaxes and moves parts of the body.
- cells here form skeletal, smooth, and cardiac muscle tissue
- voluntary muscles are made up of striated muscle tissue
- involuntary muscles are smooth muscle tissue
- the heart has its own special muscle tissue
6
Q
Nerve tissue
A
Makes up the nervous system.
- Carries messages from the brain and coordinates all body functions
- made of neurons (brain, spinal cord, and nerves)
- the neuron receives and conducts electrochemical impulses from one part of the body to another. It’s function is to control and coordinate activities of the body.
7
Q
Organs
A
Are groups of tissues designed to perform specific functions.
(Brain, heart, eyes, kidney, liver)
8
Q
Systems
A
These are groups of organs which co-operate for a common purpose.
The human body consists of 11 major systems
9
Q
Name the 11 body systems
A
Integumentary system (the skin)
Respiratory system
Digestive system
Urinary system
Reproductive system
Skeletal system
Muscular system
Nervous system
Cardiovascular system
Lymphatic system
Endocrine system
10
Q
What are the basic building blocks for our bodies tissues?
A
Protein
11
Q
Proteins are made up of:
A
Amino acids and enzymes
12
Q
Thickness of skin varies according to:
A
Body part, age and race
13
Q
Skins most amazing ability;
A
Ability to heal itself through hyper production of cells and blood clotting
14
Q
What are the functions of the skin? (6) PHASES
A
- Protection
- Sensation
- Heat regulation
- Excretion
- Secretion
- Absorption
15
Q
The skin is a protective barrier to:
A
Outside elements and microorganisms
It has many defence mechanisms to protect the body from injury or invasion.
16
Q
Acid mantle:
A
Is the protective barrier made up of sebum, lipids, sweat and water that form a hydrolipidic film to protect the skin from drying out and from exposure to external factors.
17
Q
Sebum:
A
Is oil on the epidermis that gives protection
18
Q
Damage to the skin barrier is the cause of many skin problems including:
A
Sensitivities, aging and dehydration
19
Q
Skin can repair itself when injured, protecting the body from infections and damage from injury through:
Hint: these cells are activated to rejuvenate and repair the skin
A
Fibroblast cells
20
Q
The barrier function is the skins mechanism that protects us from:
A
Irritation and (TEWL) Trans epidermal water loss
21
Q
What does the skin produce as another form of protection from the sun?
A
Melanin
22
Q
Melanin
A
Is the pigment in the eyes, hair and skin that gives us some protection from UV rays
23
Q
The body maintains a constant temperate of 37• to prevent:
A
Evaporation of fluids
24
Q
An increase or decrease in the outside temperature results in:
A
Vasodilation or Vasoconstriction
25
Vasodilation
We cool ourselves by evaporation through the sweat glands. Blood vessel dilation also assists in cooling the body.
26
Vasoconstriction
We protect ourselves from cold by constriction of the blood vessels and decreasing blood flow to extremities therefore the major organs are receiving majority of the blood supply.
27
Hair follicles can also help regulate:
| And protects us from:
Hair follicles can help regulate body temperature and protect us from heat loss.
28
Which muscle contracts and causes goosebumps to warm the skin?
Arrector Pili muscle
29
Vasodilation
Protects the body from heat
- increase in diameter of blood vessels
- skin is pink and warm
- caused by relaxation of smooth muscle
- blood in the skin moves more freely
- surface heat is lost and body temperature is reduced through perspiration
30
Vasoconstriction
- protects the body from cold
- contraction of the smooth muscle
- passage of blood slows, skin pales, a bluish cast may be noticed (loss of oxygen)
- the arrector pili muscle can cause the hairs to rise closing the surface skin, keeping body heat inside
31
Absorption
Absorption of ingredients, water, and oxygen is necessary for our skins health.
32
The skin absorbs:____ and discharges:___
The skin absorbs oxygen and discharges carbon dioxide
33
The skin selectively absorbs topical products and creams through:
The cells, hair follicles and sebaceous glands.
34
Which products penetrate better?
Lipid-soluble
35
Absorption of UV in the skin layers forms:
Vitamin D
36
The route of penetration into the skin are:
Through the follicles, sebaceous glands, intercellular (between the cells), trans cellular (across / through the cells)
37
What are the layers of the skin?
1. Epidermis (outer layer)
2. Dermis (intermediate layer)
3. Hypodermis or subcutaneous cellular tissue (inner layer)
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The epidermis is composed of _ tissue
Stratified epithelial tissue
(Protection)
Think of main function of the outside
39
The dermis is composed of _ tissue
Connective tissue
40
The hypodermis is composed of _ tissue
Connective adipose tissue
41
How many layers thick is the epidermis?
5
42
Epidermis
- Non- vascular = lack of blood vessels
- Outermost layer
- composed of 5 types of cells:
1. Stem cells
2. Keratinocytes
3. Melanocytes
4. Tactile cells (merkel)
5. Langerhans cells
43
Keratinocytes (keratin protein cells)
- Comprise 95% of the epidermis (found in all layers)
- surrounding the cells are lipids which prevent water loss and dehydration
- keratin is a fibrous protein that provides resiliency and protection to the skin
44
The five types of cells in the epidermis
1. Stem cells - replacement cells (repair)
2. Keratinocytes - produce keratin & majority of the epidermis is composed of these
3. Melanocytes - produce melanin
4. Tactile cells (merkel cells) - sensory cell
5. Dendritic (immune cells/ langerhans cell)
45
5 layers of the Epidermis
| (from bottom upward)
1. Germinative layer/ stratum germinativum/ stratum basale
2. Prickle cell layers/ Stratum Spinosum/ spiny layer
3. Granular layer/ stratum granulosum
4. Clear layer/ stratum lucidum
5. Horney layer/ stratum corneum
46
Epidermis:
- Avascular/ non-vascular layer (lack of blood vessels)
- Outermost layer of the skin
- 0.04 to 1.5mm thick
- composed of five types of cells
1. Stem cells
2. Keratinocytes
3. Melanocytes
4. Tactile cells
5. Langerhans cells
47
Germinative layer
- located at the basale membrane (above the dermis)
- composed of a single layer of cells which constantly divide and give birth to new cells that makeup all other layers above the germinative layer
- considered the most active layer because mitosis occurs here
- stem cells are basically mother cells that divide to produce daughter cells
- specialized melanocytes are distributed throughout the layers
- tactile cells are receptors for touch
48
Fibroblast cells
Help to rejuvenate and repair the skin
49
Sebum
Is an oily substance that protects the surface of the skin.
It lubricates the skin and hair.
Sebaceous glands are attached to follicles that produce (secrete) sebum.
Sebum on the skin slows down the evaporation of water. Also known as Trans Epidermal Water Loss (TEWL)
50
When does mitosis mostly occur?
At night time
51
What is: Melanogenisis
Is a highly complex process of melanin production.
52
What 3 factors initiate melanogenesis:
1. Melanocyte stimulating hormone (MSH)
2. Adrenal corticotropic hormone
3. Exposure to ultraviolet light and inflammation
53
To make a protein the body needs 2 things:
An amino acid and an enzyme
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Tyrosine and tyrosinase
Tyrosine: is an amino acid
Tyrosinase: is an enzyme
Necessary for production of melanin
55
Explain melanogenesis
The production of melanin
It is initiated by 3 factors: MSH melanocyte stimulating hormone, adrenal corticotropic hormone, and exposure to UV light and inflammation
Melanin is a protein. To make a protein the body needs an amino acid and enzyme.
Tyrosine is the amino acid
Tyrosinase is the enzyme
Once the pigment production is triggered (which can be by many factors like UV, hormones, etc) the pituitary gland produces a peptide hormone (MSH) which signals the melanocytes to start producing melanin.
Once melanin is formed it is packaged into melanosomes which are then transferred into keratinocytes
The keratinocyte starts it journey moving upward through the epidermis and undergo keratinization until it reaches the surface of the skin and is sloughed off
56
Which internal and external factors can affect melanin activation and productions?
Internal: hormones, inflammatory response
External: UV and chemical exposure
57
Desmosomes
Keratin filaments. The protein bonds that create the junction between cells.
58
Langerhans cells
- They alert the immune system.
- They sense unrecognized foreign invaders (bacteria) and then process these antigens for removal through the lymphatic system
- They are present in all layers of the epidermis but are most prominent in the stratum spinosum (prickle cell layer)
59
Granular layer/ Stratum granulosum
- production of keratin and intercellular lipids
- enzymes dissolve structures that hold cells together
- composed of 3-5 layers of flattening granular cells
- natural moisturizing substances are made here and form components of the skins waterproofing barrier (triglycerides, waxes, fatty acids)
- these water-soluble compounds are referred to as NMF’s (natural moisturizing factors) and hydrate the lipids layer, absorb water, and prevent water loss.
- cells start to die here because enzymes are released which destroy the nucleus
60
Clear layer (stratum lucidum)
- thin, clear layer of dead skin cells under the stratum corneum
- the keratinocytes in the layer contains clear keratin
- cells here release lipids forming bilayers of oil & water
- this layer is thickest on the palms of the hands and soles of the feet
- composed of epidermal ridges to provide better grip
- this layer forms our unique fingerprints and footprints
- keratinocytes are packed with eleidin
- cells have no nuclei or other organelles
61
Horney layer/ Stratum corneum
- consists of 30 layers of dead, scaly, keratinized cells
- resistant to abrasion, penetration, and water loss
- cells and oil combine to form a protective barrier layer called the acid mantle
- keratinocytes have hardened into comeocytes (the waterproof, protective cells which have dried out and lack nuclei)
- keratinocytes are continuously shed from the skin - that process is called DESQUAMATION
- it approximately takes 2 weeks for cells to be pushed out once they have entered this layer
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What is desquamation:
When cells are replaced by new cells coming to the surface from the lower stratum
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The dermis:
- 25 times thicker than the epidermis
- this connective tissues provides framework to support epithelial and other tissues
- has an essential role in: TRANSPORTATION, PROTECTION, and REPAIR
- this tissue contains matrix
- supplies skin with oxygen and nutrients
All found in the dermis:
Collagen - a protein that gives skin its strength and is necessary for wound healing.
Elastin - fibrous protein that forms elastic tissue and gives skin elasticity
Fibroblasts - cell stimulators (help make collagen and elastin)
Lymphocytes - fight infection
Langerhans cells - guard/ immune cells
Mast cell - allergic reactions
Leukocytes - white blood cells which fight infections
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Fibroblasts
Help in the production of collagen and elastin
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Glycosaminoglycan (GAG)
Large protein molecules and water binding substances found between the fibres of the dermis
Gags are polysaccharides (protein and sugar)
66
Hyaluronic acid
Part of the dermal substance
Stores H2O, salts and glucose temporarily
67
Dermal/ epidermal junction
Connects the dermis to the epidermis
Rete ridges anchors them together
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What are the 2 layers of the dermis?
1. Papillary (upper portion)
| 2. Reticular
69
What are the two types of thermo-receptors?
1. End of bulbs Krause
| 2. Corpuscles of Raffini
70
Papillary layer of the dermis
- most active layer
- forms the epidermal dermal junction
- important in repair of all tissue
- papillary layer comprises of 10-20% of the dermis layer
- most connective tissues cells are found here
71
Reticular layer of the dermis:
- Makes up most of the dermis
- elements are the same as the papillary layer but they are far denser here
- damage to elastin fibres as they break down are the primary cause of sagging, wrinkles, and aging
- stretch marks are caused by damaged elastin fibres
- collagen and elastin are broken down by UV damage and other factors
72
Hypodermis
- connective adipose tissue in which many cells are filled with fat
- 80% fat
- stores food which may be oxidized thus producing energy
- reduces heat loss and acts as a shock absorber

73
Nerves
Skin contains fine endings of nerve fibres which pick up sensations and relay messages for the body.
- they are associated with pain and itching and their endings are closely situated in the epidermal tissue
Nerves in the skin can be classified into three types:
1. Sensory
2. Motor
3. Mixed 
74
Sensory nerves
Nerve fibres send messages to the central nervous system and brain to react to heat cold pain pressure touch and itching.
These are situated in the epidermal tissue
75
Motor nerves /secretory
Relay messages from the brain and spinal cord to muscles or glands
Work on voluntary and involuntary muscles to cause movement
Secretory nerve fibres are motor nerves attached to sweat glands and control sebum output to the surface of the skin
76
Mixed nerves
a nerve composed of both sensory and motor fibres
77
Sebaceous gland
Sebum (oil) secretory gland
Sebum helps create the acid mantle which protects the skin
Sebaceous glands are larger on the face and scalp
Keeps skin soft & supple
Located at the hair follicle
Very active during puberty
78
Sudoriferous gland (sweat gland)
This gland helps regulate body temperature and eliminate waste products by excreting sweat.
The excretion of sweat is controlled by the nervous system. 
79
Eccrine sweat gland
Everywhere on the body. Primarily on the forehead, palms and soles.
These glands are not connected to hair follicles
Adult skin has 3-4 million of these
More active during physical activity and high temperatures
Sweat is 99%water and has a PH 4-6
This does not produce an odour
80
Apocrine sweat glad
Found in the under arms, genital, anal canal, areola, and beards
 respond to stress and sexual stimulation
Produce pheromones (The chemical that influences physiology or behaviours of other members of the species)
Produces alkaline secretions
Becomes functional with puberty
Odour associated with these glands due to the interaction of secretions and bacteria on the skin
Secretes into the hair follicle
81
Hair follicle
Hairs are keratinized (made from protein of keratin)
Sometimes more than one hair grows out of the follicle
Hair is tough and elastic
The base of the follicle surrounds the nourishment source for the matrix called the dermal papilla
