2. Cells & Tissues Flashcards
Define the terms cell, tissue and organ.
- Cell: living single fundamental, structural and functional unit.
-
Tissue: collection of specialised cells united in a matrix for the performance of a particular
function. - Organ: complex collection of tissues combined to perform the organ’s function(s).
Describe the structure of skin as an organ.
- Which tissues?
- Which cells?
Skin as the Organ
Tissues:
- Epithelium
- Connective tissue
- Blood vessels
- Nerves
– Cells:
- Squame, cuboidal epithelial cell and basal stem cell (epithelium)
- Fibroblast (connective tissue)
- Melanocyte (located in epithelium)
- Adipocyte (fat)
- Endothelium
- Smooth muscle
What is the histological structure of skin and the components of the skin layers?
Skin layers
-
Epidermis (E)
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
-
Dermis
- Reticular dermis (R)
- Hypodermis (H)
What type of epithelium is the epidermis?
- 2 main cell types?
- 5 Layers - CLGSB?
- Which layer is only present in thick skin?
- Which layer has keratohyalin granules?
- What shape are the cells of the stratum basale? What do they rest on?
Epidermis
- The outer layer.
- Stratified squamous epithelium.
- Includes melanocytes and keratinocytes.
Cairn’s Ladies Give Superb Backrubs- Mnemonic for STRATA (superficial to deep)
- Corneum (oldest cells) - Very flattened, desiccated cells with keratin
- Lucidum - Present only in thick skin (thick skin has a thicker epidermis with no hair)
- Granulosum - Contain keratohyalin granules
- Spinosum - Several cells thick & Cells have cytoplasmic processes or spines
- Basale (youngest & stem cells) - Single layer of cuboidal stem cells resting on basal lamina
At dermal epithelial junction = basement membrane
Which layers of the skin can be seen here?
Epidermis (E)
Reticular Dermis (R)
What are we looking at here?
No hair so = thick skin
Which feature of the stratum granulosum is labelled here? (Both arrows pointing to same thing)
Which cells of the stratum spinosum are labelled here?
Which cells are circled here?
- In which stratum of the epithelium do they reside?
- What is their function?
= melanocytes in the stratum basale
Melanocytes (pigmentation):
- Scattered through basal layer of epidermis.
- Mature melanin is transferred to keratinocytes.
- Appear paler
Which cells are labelled here?
Which cells deliver melanin to the epithelial cells of the basal layer?
= melanocytes
What are the strata 1-5 of the epidermis?
Cairn’s Ladies Give Superb Backrubs
Corneum, Lucidum, Granulosum, Spinosum, Basale
What are the 2 structural layers of the dermis and their contents?
- What kind of CT forms the reticular dermis?
- Where do Langerhans cells reside? What are they?
- What kind of CT forms the hypodermis?
Dermis
-
Reticular dermis
- Accessory glands
- Roots of hairs
- Dense collagen fibers of the connective tissue - Mostly think bundles of collagen and elastin
- Blood vessels and their component cells
- Resident macrophages the Langerhan’s cells
- Nerve bundles
- Ground substance (hydrated gel of the extracellular matrix)
Hypodermis (Subcutis)
- Loose connective tissue - Fine fibrils of collagen, reticulin, elastin
- Ground substance (hydrated gel of the extracellular matrix)
- Blood vessels and their component cells
What are the 2 types of sweat glands?
- Where are they found?
- Which type are associated with hair follicles?
- Which type begin their function at puberty?
- Where are there no sweat glands?
Two types of sweat glands in Reticular Dermis
- Apocrine - Large, open into hair follicle, begin function at puberty (genital areas, armpits)
-
Eccrine - open into pores leading to surface
- Wide distribution all over body
- Most numerous on palms and soles, intermediate-density on scalp, less dense on arms, legs and trunk
- Except NONE on lips, concha [outerear], glanspenis, inner surface of prepuce [foreskin], labia minora and clitoris
What are these?
= sweat glands (eccrine & apocrine)
What do sebaceous glands do? What are they usually attached to?
Sebaceous glands: Secrete an oily substance called sebum - usually attached to hair follicles
What glands are these?
How can you differentiate between a sweat and sebaceous gland on a histological slide?
Green arrows? Black arrows? Orange arrows?
Sweat glands have nuclei all the way around the base, sebaceous glands are located near hair sheaths and look like big sacs of potatoes.
What forms the pilosebaceous unit?
= The pilosebaceous unit is composed of a hair follicle, arrector pili muscle, and sebaceous gland.
Label the components of the pilosebaceous unit.
Label the components of the hair.
Label the hair in cross section.
What are 2 nerve endings found in skin?
Nerve endings
- Pacinian corpuscle: mechanoreceptor – touch/vibration (diagram on left)
- Meissner corpuscle: mechanoreceptor – touch (diagram on right)
What is the structure of the basement membrane in skin?
How does it appear on an EM? and an LM?
