Unit 2 (all cards) Flashcards
True or false: Tight junctions function primarily to prevent cells from pulling apart.
False; it’s to keep stuff from getting in
The type of secretion where the entire cell dies and the cell fragments are mixed with the produced cellular substance is called a ____ secretion.
holocrine
A second degree or “partial thickness burn” is when:
a burn is through the epidermis and part of the dermis.
True or false: Fibrosis repairs a tissue and restores the original cells and function of the tissue.
False; Fibrosis replaces damaged tissue mainly with collagen. This does not restore the original function.
This tissue is found lining the kidney tubules and functions in absorption and excretion.
simple cuboidal epithelium
What tissue comprises tendons and ligaments?
dense regular connective tissue
True or false: Hyperplasia is the term for increased cell production in a tissue.
True
True or false: Melanin has the greatest influence on your skin tone, but hemoglobin and carotene also contribute to the final tone.
True
Sudoriferous glands include what types of glands
Apocrine and merocrine
True or false: Merocrine gland secretions are involved in scent communication, not in thermoregulation.
False; that’s apocrine glands. Merocrine glands are involved in thermoregulation.
___________________ is the most common but least dangerous type of skin cancer, and occurs in the cells of the stratum basale.
basal cell carcinoma
True or false: When looking at the layers of the epidermis, everything superficial to the stratum granulosum is dead.
True
Dense irregular connective tissue is found in the ______ layer of the _____.
reticular layer of the dermis
Due to the force of muscle contraction and stretching from the loading of blood, heart tissue is under a lot of mechanical stress. Because of this you would not be surprised to learn that cardiac muscle cells are connected by:
desmosomes
The growth of bones in length is the result of ____ ossification.
endochondral
If you want to lower blood calcium, which hormone(s) will be released?
Calcitonin
Because of the action of osteoblasts, which way will calcium ion concentration travel?
from blood to bone
To lower blood calcium, which action might a hormone do?
inhibit osteoclast activity
True or false: bones of the fingers are an example of long bones
True
True or false: Red bone marrow is found in all bones of the adult skeleton.
False; primarily found in the axial skeleton
The hardness of bone is thanks to the presence of:
hydroxyapatite and other minerals
The most common bone disease/disorder is:
Osteoporosis
The uniquely shaped ends of long bones are called the:
epiphyses
True or false: The femur of a 5 year old child will have epiphyseal lines.
False; a young child would still have growth plates present.
Give an example of a sesamoid bone
Patella
The pancreas is located below/behind the stomach. What abdominal quadrant would it mostly belong in?
left upper
The pancreas belongs to two different organ systems. It produces important enzymes for breakdown of food, and it produces hormones to regulate our blood glucose. These functions would place it in which two systems?
digestive and endocrine
True or false: An epithelial tissue that has multiple layers of cells is more likely to be found in an area where rapid diffusion takes place.
False
Where would you find transitional epithelium?
Urinary bladder
Which type of tissue is found on the ends of bones in most movable joints?
hyaline cartilage
Which type of tissue lines the trachea and bronchi and has cilia and goblet cells?
pseudostratified columnar epithelium
What is the tissue that makes up tendons and ligaments?
Dense regular connective tissue
What type of tissue is found in the epidermis?
keratinized stratified squamous epithelium
Which type of receptor is found in the lower part of the dermis and detects deep touch/pressure and vibration?
lamellar (Pacinian) corpuscles
What is the deepest layer of the epidermis?
stratum basale
Which layer of the epidermis is composed of the preserved membranes of dead cells?
Stratum corneum
What is the difference between thick and thin skin?
The presence of a stratum lucidum
Microvilli are folds of the cell membrane that increase the surface area of the cell/tissue. Which tissue has microvilli, and where is it found?
simple columnar, digestive tract
Which tissue type has loosely scattered cells and more prominent extracellular matrix?
Connective
If you injure a disk in your back, what kind of cartilage has been damaged?
Fibrocartilage
In our chapter 7 notes we introduced the idea of feedback loops. Feedback loops enable the body to recognize a change, make a decision about the change, and enact responses. Let’s practice recognizing the components of a feedback loop.
The healthy pH range of the blood is 7.35-7.45. When you engage in strenuous exercise, muscles remove oxygen from the blood for energy processes, which lowers the blood oxygen level. At the same time, carbon dioxide blood levels climb, which lowers the blood pH. Chemical sensors in blood vessels detect these changes and send feedback to the brainstem. The brain responds by sending a signal to the muscles of respiration for increasing the rate and depth of breathing, which increases the intake of oxygen and the removal of carbon dioxide from the blood. As carbon dioxide is removed from the blood, the pH rises again. In this example of a feedback loop, the effector and stimulus would be:
Effector: the muscles of respiration
Stimulus: blood pH and CO2 levels
What are the two most durable components of your body?
Bones and teeth (especially the enamel)
Do we have a dead or living skeleton?
Living
True or false: The skeletal system constantly remodels itself and interacts with other organ systems of the body
True
______ is the study of bone
Osteology
What are the 3 main components of the skeletal system?
Bones, cartilages, and ligaments
Define cartilage, ligaments, and tendons
Cartilage is forerunner of bone formation and coats ends of bones.
Ligaments connect bone to bone
Tendons connect muscle to bone
What are the functions of the skeleton?
Support, protection, movement, electrolyte balance, acid-base balance, and blood formation
How does the skeleton aid in support, protection, and movement?
Support: limb bones and vertebrae support body; jaw bone supports teeth; bones support viscera
Protection: of brain, spinal cord, heart, lungs etc
Movement: of limbs, breathing – action of muscles on bones
How does the skeleton aid in maintaining electrolyte and acid base balances, and how does it aid in blood formation?
Electrolyte balance: calcium & phosphate levels
Acid–base balance: buffers blood against large pH changes by altering phosphate and carbonate salt levels
Blood formation: red bone marrow makes red blood cells
Define bone (osseous tissue)
A connective tissue with its matrix hardened by calcium phosphate and other minerals
Define mineralization/ calcification
The hardening process of bone
What do individual bones consist of?
Individual bones (organs) consist of bone tissue, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue
Define sesamoid and sutural bones
Sesamoid (type of short bone) and sutural (wormian) bones
Sesamoid bones develop in a tendon (or ligament) in response to a need for more leverage
Sutural bones are the extra bones in the sutures (especially the lambdoid suture) of the skull
Define compact bone
Has a dense outer shell of bone
Define spongy (cancellous) bone
Made up of an internal honeycomb of trabeculae filled with red or yellow bone marrow
The skeleton’s weight is made up of ___% compact bone and _____% spongy bone
75% compact bone; 25% spongy bone
Define diaphysis and epiphyses
Diaphysis—shaft that provides leverage
Epiphyses—enlarged ends of a long bone
Define the epiphyseal line (metaphysis) and marrow cavity (medullary cavity)
Epiphyseal line: separates diaphysis from epiphysis (aka metaphysis)
Marrow cavity: space in the diaphysis of a long bone that contains bone marrow (aka medullary cavity)
Define articular cartilage
A layer of hyaline cartilage that covers joint surface and allows the joint to move more freely
Describe the two layers of the periosteum
Outer fibrous layer made of collagen
Some fibers continuous with tendons
Perforating fibers —penetrate into bone matrix
Inner osteogenic layer of bone-forming cells
Important to bone growth and healing of fractures
Define the periosteum
2 layers covering most of bone
Define the endosteum
A thin layer of reticular connective tissue lining marrow cavity
Contains osteoblasts and osteoclasts
The nutrient foramina is penetrated by what?
Blood vessels
Describe the epiphyseal plate (growth plate)
Area of hyaline cartilage that separates epiphyses and diaphyses of children’s bones
Enables growth in length
When growth is finished turns into Epiphyseal line
List the 8 features of long bone
Epiphyses Diaphysis Compact bone Spongy bone Marrow cavity Articular cartilage Periosteum Endosteum
Describe the anatomy of a flat bone
Bones with a sandwich-like structure: two layers of compact bone with a middle layer of spongy bone (diploë)
Define and describe the diploë of flat bones
Diploë is the spongy middle layer found in flat bones. It absorbs shock and the marrow spaces are lined with endosteum
Define osteogenic cells
Stem cells (cell division) and develop into osteoblasts
Define osteoblasts
Bone-forming cells
Describe how osteoblasts do their job
Osteoblasts secrete collagen (and other carbohydrate-protein complexes) to form a soft fibrous matrix. This matrix hardens with mineral deposition. They make bone by mitosis and differentiation of osteogenic cells
What two organelles are particularly abundant in osteoblasts?
Rough ER and golgi complexes.
What stimulates osteogenic cells to multiply rapidly? What does this do?
Stress stimulates osteogenic cells to multiply rapidly, which increases the number of osteoblasts which reinforce bone
Define and describe osteocytes
Defined as mature bone cells
They’re found in pockets called lacunae, and connected to each other by canaliculi and gap junctions
Some reabsorb bone matrix & others deposit it; regulates bone remodeling
Describe the role of osteocytes when under stress
They act as strain sensors; when stressed, they produce biochemical signals that regulate bone remodeling (shape and density changes that are adaptive)
Define and describe osteoclasts
Defined as bone-dissolving cells found on bone surface
Derived from fusion of multiple white blood cells (WBC’s)
Usually multinucleate
Secrete enzymes and acids for the break down of bone (resorption)
True or false: Dissolving bone is a part of bone remodeling
True
What are the two main parts of the matrix, and what fraction of the matrix do they each make up?
Organic portion (1/3) and inorganic portion (2/3)
Describe the organic part of the matrix
Synthesized by osteoblasts
Composed of collagen and carbohydrate–protein complexes
Responsible for the flexibility of bone
Makes up 1/3 of the matrix
Describe the inorganic part of the matrix
85% hydroxyapatite (calcium phosphate) 10% calcium carbonate 5% other minerals (fluoride, sodium, potassium, magnesium) Responsible for the hardness of bone Makes up 2/3 of the matrix
If there is a mineral deficiency, what happens to the bone?
Rickets disease
Describe Rickets disease
A disease caused by mineral deficiency and resulting in soft, deformed bones
If there is a defect in collagen deposition, what happens to the bone?
Osteogenesis imperfecta (brittle bone disease)
Describe osteogenesis imperfecta (brittle bone disease)
Results from a defect in collagen deposition
Histology of compact bone reveals that they have _____
Osteons (haversian systems)
Describe the 3 elements of the haversian system of an osteon
1) Lamellae
Columns of the matrix (mainly collagen) that are weight bearing
Run concentric, circumferential, and interstitially
2) Central (Haversian canal)
Contains blood vessels and nerves
3) Perforating (Volkmann’s) canals
Channels that connect blood and nerves from periosteum to the central (Haversian) canal
Describe lamellae in osteons
Columns of the matrix (mainly collagen) that are weight bearing. The columns run concentric, circumferential, and interstitially
Describe the central (Haversian) canal of the osteon
Contains blood vessels and nerves
Describe the perforating (volkmann’s) canals of osteons
Channels that connect blood and nerves from periosteum to the central (Haversian) canal
Run transverse or diagonal
Where do trabeculae develop in spongy bone?
They develop along the bone’s lines of stress
Something described as a “lattice of bone covered with endosteum” is known as what?
Spongy bone
Describe the structure and function of spongy bone
Structure: It’s a lattice of bone covered with endosteum; made up of trabeculae (thin plates of bone) that develop along the bone’s lines of stress, and the spaces are filled with red bone marrow. Has few osteons and no central canals
Function: Provide strength with minimal weight
Define bone marrow
Soft tissue occupying marrow cavities of long bones and small spaces of spongy bone
What are the two types of bone marrow?
Yellow and red
Describe red bone marrow
- Contains hemopoietic tissue—produces blood cells
- Found in nearly every bone in a child
- In adults, it’s found in the skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur
Describe yellow bone marrow
- Found in adults
- Stores Triglycerides
- Can transform back to red marrow in the event of chronic anemia
Describe where red bone marrow is found in children and adults
Infants – in nearly every bone
- medullary cavity
- all areas of spongy bone
Adults
- head of the femur and humerus
- diploë (spongy bone) of flat bones
- some irregular bones (such as hip and vertebrae)
Define ossification or osteogenesis
The formation of bone
In the human fetus and infant, bone develops by what two methods?
Intramembranous ossification
Endochondral ossification
When does intramembranous ossification occur?
It produces the flat bones of skull and clavicle in fetuses (and ossifies the fontanels, and thickens long bones throughout life)
During intramembranous ossification, bone develops within what kind of membrane?D
A fibrous connective tissue membrane
Describe the life-cycle of an osteocyte formed by intramembranous ossification
Mesenchymal cells turn into osteoblasts which turn into osteocytes (spongy bone)
Describe intramembranous ossification
Bone develops within a fibrous connective tissue membrane (Mesenchymal cells to osteoblasts to osteocytes (spongy bone))
Forms the flat bones of the skull, clavicles, and ossifies the fontanels.
Most of these bones are remodeled (destroyed and reformed) as we grow to adult size.
Describe endochondral ossification
Bone forms by replacing hyaline cartilage
Forms most the bones of the body below the skull (except the clavicle)
Mesenchyme turn into chondroblasts, which die and are replaced by osteoblasts, which form spongy bone, which forms compact bone
What type of ossification is best described as “bone is formed by replacing hyaline cartilage”?
Endochondral ossification
In endochondral ossification, what do primary and secondary ossification form?
Primary Ossification: forms diaphysis
Secondary ossification: forms epiphysis
When do epiphyseal plates close? What does this mean for growth?
Close in late teens to early 20s, which is when bone can no longer grow in length
During infancy and childhood, in endochondral ossification the epiphyses fill with _______ bone
spongy
Describe the role of cartilage in endochondral ossification
Cartilage is limited to the articular cartilage covering each joint surface, and to the epiphyseal plate
Describe the role of the epiphyseal plate in bone growth
Serves as a growth zone for bone elongation, covered with cartilage
True or false: bones grow in two directions, which are length and width
True
True or false: Ossification continues throughout life with the growth and remodeling of bones
True
Describe how bones grow in length
Occurs at Epiphyseal plates
Cartilage cells undergo mitosis, pushing the epiphysis away from the diaphysis
Cartilage cells die and are replaced by bone.
When growth is finished, there’s no more cartilage at the plate, which then becomes an epiphyseal line, and bone can no longer grow in length
Describe achondroplastic dwarfism
Long bones stop growing in childhood
Normal torso, short limbs
Failure of cartilage growth in metaphysis
Spontaneous mutation produces mutant dominant allele
Describe pituitary dwarfism
Lack of growth hormone
Normal proportions with short stature
Describe how bones become wider/thicker
Happens through appositional growth: continual growth in diameter and thickness throughout the lifespan through intramembranous ossification.
Osteoblasts of inner periosteum deposit osteoid tissue
Lay down matrix in layers parallel to surface
Forms circumferential lamellae
Osteoclasts of endosteum enlarge marrow cavity
Define appositional growth and where it happens
The growth of bone horizontally; happens on the surface of bone
About ___% of an adult’s skeleton is remodeled each year
10%
What are the two main types of cells involved in bone remodelling?
Osteoblasts: Bone deposition
Osteoclasts: Bone resorption
Describe Wolff’s Law of Bone
Bone grows or remodels in response to the demands placed on it
Exercise: promotes bone growth
Lack of exercise (bedridden): atrophies bones
Define mineral deposition/ mineralization
The process in which calcium, phosphate, and other ions are taken from blood and deposited in bone
Describe the process of mineral deposition/ mineralization
Osteoblasts produce collagen fibers
Fibers become encrusted with minerals
First few crystals act as seed crystals that attract more calcium and phosphate
Abnormal calcification (ectopic ossification)
Formation of a calculus (calcified mass) in lung, brain, eye, muscle, tendon, or artery (arteriosclerosis)
Define mineral reabsorption
The process of dissolving bone and releasing minerals into blood
Describe the process of mineral reabsorption
Performed by osteoclasts
Pump hydrogen to extracellular fluid (chloride follows). Hydrochloric acid (pH 4) dissolves bone minerals
Produce an enzyme which digests collagen in an acidic environment
Describe the role of osteoclasts and osteoblasts in braces
Braces reposition teeth, which move because osteoclasts dissolve bone ahead of the tooth; osteoblasts deposit bone behind the tooth
Describe the role of the bone matrix in homeostasis
Minerals are deposited in the skeleton and withdrawn from the skeleton when they are needed for other purposes
Phosphate is a component of DNA, RNA, ATP, phospholipids, and pH buffers
Calcium needed in neuron communication, muscle contraction, blood clotting, and exocytosis
What is phosphate a component of?
DNA, RNA, ATP, phospholipids, and pH buffers
What is calcium needed for in the body?
Neuron communication, muscle contraction, blood clotting, and exocytosis
True or false: Calcium and phosphate are used for much more than bone structure
True
Define homeostasis
The ability to detect change, activate mechanisms that oppose it, and thereby maintain relatively stable internal conditions
Describe negative feedback
It allows for a dynamic equilibrium within a limited range around a set point.
The body senses a change and “negates” or reverses it.
The fundamental mechanism to keep body in homeostasis.
Loss of homeostatic control causes what?
Illness or death
Why are feedback loops called feedback loops?
Because feedback mechanisms alter the original changes that triggered them, they are called feedback loops.
Describe the role of homeostasis in body temperature
If too warm, vessels dilate in the skin and sweating begins (heat-losing mechanism).
If too cold, vessels in the skin constrict and shivering begins (heat-gaining mechanism).
What are the 3 main components of feedback loops?
Receptor, integration (control) center, and effector.
Define a receptor in feedback loops
Structure that senses change in the body (chemical, temperature, pain, pressure, volume, etc.)
Define an integration (control) center in a feedback loop
The control center that processes the sensory information, “makes a decision,” and directs the response (e.g., cardiac center of the brain)
Define an effector in a feedback loop
The cell or organ that carries out the final corrective action to restore homeostasis (e.g., the heart)
Define and describe positive feedback loops
It’s a self-amplifying cycle that leads to greater change in the same direction; the feedback loop is repeated (change produces more change).
It’s a normal way of producing rapid changes
(ex: childbirth, blood clotting, protein digestion, and generation of nerve signals)
However, they can sometimes be dangerous
(ex: the vicious cycle of runaway fever)
Calcium homeostasis depends on a balance between what two things?
Intake (diet) and loss (urinary and fecal eliminations)
How is calcium homeostasis maintained?
By calcium exchange between osseous tissue and blood, which is mediated by three hormones
Calcium homeostasis is regulated by what three hormones?
Calcitriol (vitamin D), calcitonin, and parathyroid hormone
Describe the role of calcitriol (vitamin D) in calcium homeostasis
It raises blood calcium levels; mainly, it increases calcium absorption by small intestine, and it also increases calcium resorption from the skeleton.
It weakly promotes kidney reabsorption of calcium ions, so less is lost in urine
Produced by actions of skin, liver, and kidneys
What is calcitriol (vitamin d) needed for in the body? What does a calcitriol deficiency result in?
Calcitriol is necessary for bone deposition; lack of calcitriol results in abnormal softness of bones.
In children, a deficiency results in rickets. In adults, a deficiency results in osteomalacia
Describe the role of calcitonin in calcium homeostasis
Produced by the thyroid gland
Its release is triggered by high blood calcium, and it lowers blood calcium concentration in 2 ways: Inhibits osteoclasts and stimulates osteoblasts
Important in children, weak effect in adults (except may inhibit bone loss in pregnant and lactating women)
What increases blood calcium? What decreases blood calcium?
Calcitriol (vitamin D) and parathyroid hormone increase blood calcium; calcitonin decreases blood calcium
Describe the role of parathyroid hormone in calcium homeostasis
PTH increases blood calcium 4 ways:
1) Stimulates osteoclast population and bone resorption
2) Promotes calcium reabsorption by kidneys
3) Promotes calcitriol synthesis
4) Inhibits osteoblasts, inhibiting bone deposition
Produced by parathyroid glands
Release triggered by low blood calcium
Describe the causes and effects of hypocalcemia
Effects: causes overly excitable nervous system and tetany (muscle spasms) (laryngospasm)
Some cases are caused by vitamin D deficiency or underactive parathyroid glands
Pregnancy and lactation increase risk of hypocalcemia
Define hypocalcemia and hypercalcemia
Hypocalcemia: low blood calcium.
Hypercalcemia: high blood calcium.
Describe the causes and effects of hypercalcemia
Makes nerve and muscles less excitable
Can cause emotional disturbance, muscle weakness, sluggish reflexes, cardiac arrest
Hypercalcemia rarely occurs
Describe bone development from infancy to early adulthood
Infancy and childhood: epiphyseal plate activity is stimulated by Human Growth Hormone (hGH)
Puberty: (testosterone and estrogens) promotes adolescent growth spurts and differentiates the male/female skeleton; bone growth ends (18 - 21 years)
At least __ or more hormones, vitamins, and growth factors affect osseous tissue
At least 20 or more hormones, vitamins, and growth factors affect osseous tissue
Why do girls grow faster than boys and reach full height earlier?
Estrogen has stronger effect than testosterone on bone growth
Describe the effects of anabolic steroids on growth
Causes bone growth to stop and the epiphyseal plate to “close” prematurely
Results in abnormally short adult stature
Define a stress fracture
A break caused by abnormal trauma to a bone
Define a pathological fracture
A break in bone that’s been weakened by disease (cancer or osteoporosis)
Fractures are classified by their structural characteristics; what are they?
Displaced vs nondisplaced
Open vs closed
Define closed reduction
A procedure to treat fractures in which bone fragments are manipulated into their normal positions without surgery
Define open reduction
A procedure to treat fractures that involves surgical exposure of the bone and the use of plates, screws, or pins to realign the fragments
Define a cast
Normally used to stabilize and immobilize healing bone
Describe osteoporosis
The most common bone disease
Affects spongy bone the most since it is the most metabolically active
Subject to pathological fractures of hip, wrist, and vertebral column
Kyphosis (widow’s hump)—deformity of spine due to vertebral bone loss
Complications of loss of mobility are pneumonia and thrombosis
The most common bone disease is __________
osteoporosis
What is kyphosis and why does it happen?
It’s a deformity of the spine due to vertebral bone loss
What demographics are most likely to get osteoporosis?
- Estrogen maintains bone density in both sexes; inhibits resorption by osteoclasts
- Postmenopausal white women at greatest risk; this is because white women begin to lose bone mass as early as age 35 and By 70, average loss is 30% of bone mass
- Osteoporosis also seen in young female athletes with low body fat causing them to stop ovulating and decrease estrogen secretion
- Risk factors: race, age, gender, smoking, diabetes mellitus, diets poor which are poor in: calcium, protein, vitamins C and
What are the treatments for osteoporosis?
- Estrogen replacement therapy (ERT) (slows bone resorption, but increases risk of breast cancer, stroke, and heart disease)
- Certain medications destroy osteoclasts
- Best treatment is prevention: exercise and a good bone-building diet between ages 25 and 40
True or false: Inspection of the skin, hair, and nails is significant part of a physical exam
True
True or false: Skin is NOT the most vulnerable organ
False; skin is the most vulnerable organ. It’s exposed to radiation, trauma, infection, and injurious chemicals
True or false: the skin receives more medical treatment than any other organ system
True
Define dermatology
The scientific study and medical treatment of the integumentary system
What are the six main functions of the skin?
1) Resistance to trauma and infection: Keratin; dermacidin & defensins; acid mantle 2) Other barrier functions: Water (protects against dehydration) UV radiation; melanin Harmful chemicals 3) Vitamin D synthesis: Skin carries out first step; Liver & kidneys complete process 4) Sensation receptors Touch, temperature, pressure, vibration, tickle, itch, and pain sensations 5) Regulation of body temperature Thermoreceptors Vasoconstriction/vasodilation If you are too warm, do cutaneous blood vessels vasodilate or vasoconstrict? Perspiration 6) Nonverbal communication
What are the two layers of the skin (cutaneous membrane)?
Dermis and epidermis
What are the two main parts of the skin?
The cutaneous membrane (the skin) and the subcutaneous layer
What type of cells is the epidermis made of?
Keratinized stratified squamous epithelium
Describe the characteristics of the epidermis
Includes dead cells at skin surface packed with tough keratin protein
5 distinct strata (layers) in thick skin; 4 strata in thin skin
Lacks blood vessels
Depends on the diffusion of nutrients from underlying connective tissue
Contains sparse nerve endings for touch and pain
List the five epidermal cell types
Stem cells, keratinocytes, melanocytes, tactile (merkel) cells, and dendritic cells
Describe stem cells in the epidermis
Undifferentiated cells that give rise to keratinocytes
In deepest layer of epidermis (stratum basale)
Describe keratinocytes
The majority of epidermal cells; Synthesize keratin
Describe melanocytes
Synthesize pigment melanin (shields DNA from UV radiation)
Occur only in stratum basale but have branched processes that distribute melanin to keratinocytes
Describe tactile (merkel) cells
Touch receptor cells in basal layer
Describe dendritic cells
Macrophages (WBCs) that are part of the immune system
Found mainly in stratum spinosum and granulosum
Describe thick skin and where it’s found
Lacks hair follicles and sebaceous (oil) glands
Has stratum lucidum
Generally has more sweat and sensory receptors
Epidermis 0.5 mm thick
Found on palms of hands and soles of feet
Describe thin skin
Possesses hair follicles, sebaceous glands, and sweat glands
Epidermis about 0.1 mm thick
Name the layers of the epidermis from deepest to shallowest
Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum
Describe the stratum basale
Single layer of stem cells and keratinocytes
Stem cells divide and give rise to keratinocytes that migrate toward skin surface to replace lost cells
Also contains a few melanocytes and tactile cells
Deepest epidermal layer
Describe the stratum spinosum
Several layers of keratinocytes joined together by desmosomes and tight junctions
Named for appearance of cells after histological preparation (spiny)
Also contains some dendritic cells
Describe the stratum granulosum
Three to five layers of flat keratinocytes
Cells contain dark-staining kerotohyalin granules
Describe the stratum lucidum
Thin, pale layer found only in thick skin
Describe the stratum corneum
20-30 layers of dead, scaly, keratinized cells
Resists abrasion, water loss, penetration of bacteria and chemicals
Describe the life history of a keratinocyte
Stem cells divide producing keratinocytes.
New keratinocytes push older ones toward the surface
Over time, keratinocytes flatten, produce more keratin and membrane-coating vesicles that release lipids that waterproofs the cell.
How long does it take keratinocytes to reach the surface layer of skin?
Take about 30-40 days – slower in old age and faster in injured or stressed skin (calluses or corns).
Where does mitosis occur in keratinocytes?
Keratinocytes in the deepest part of stratum spinosum can also divide. Mitosis requires abundant oxygen and nutrients, so once cells migrate away from blood vessels of the dermis, mitosis cannot occur
Describe the function of the epidermal water barrier
Water retention is fostered by tight junctions between skin cells and the waterproofing that occurs in the stratum granulosum
Helps prevent dehydration
Does not prevent the absorption of water by the stratum corneum when we soak in a bath (“prune fingers”)
What are the layers of the dermis? (in order from shallow to deep)
Papillary layer and reticular layer
Describe the papillary layer of the dermis
Most superficial layer of the dermis
Thin zone of areolar tissue in and near the dermal papilla
Anchors epidermis to dermis
Rich in small blood vessels
Contains Tactile (Meissner) corpuscles (touch) and free nerve endings (pain and temperature)
Describe the reticular layer of the dermis
The deeper and thicker layer of dermis
Consists of dense, irregular connective tissue
Packed with oil glands, sweat glands, hair follicles, etc.
Stretch marks (striae): tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity
Contains Lamellar (Pacinian) corpuscles for pressure reception
Describe the formation of fingerprints
Dermal papillae are more pronounced in thick skin (palms, soles, etc.)
As epidermis conforms to papillae, epidermal ridges are formed
Increases friction – better grip
Describe the hypodermis
Has more areolar and adipose than dermis
Common site of drug injection since it has many blood vessels
Subcutaneous fat used for energy reservoir and thermal insulation
Thicker in women
Thinner in infants and elderly
Describe the 3 main things that contribute to skin color
1) Melanin
Produced by melanocytes, accumulates in keratinocytes
People of different skin colors have the same number of melanocytes but differ on the amounts of melanin
2) Hemoglobin
pigment in red blood cells; adds reddish to pinkish hue to skin
3) Carotene
yellow pigment acquired from egg yolks and yellow/orange vegetables
Concentrates in stratum corneum and subcutaneous fat
Describe melanin
Eumelanin—brownish black
Pheomelanin—reddish yellow (sulfur-containing)
Darker skinned people:
Produce greater quantities of melanin
Melanin breaks down more slowly
Melanin granules more spread out in keratinocytes
Melanized cells seen throughout the epidermis
Lighter skinned people:
Melanin clumped near keratinocyte nucleus
Little melanin seen beyond stratum basale
Exposure to UV light stimulates melanin secretion and darkens skin
This color fades as melanin is degraded and old cells are exfoliated
List the different types of skin color/tone and describe what conditions are associated with them
Cyanosis—blueness due to oxygen deficiency
Erythema—redness due to increased blood flow to skin
Pallor—paleness due to decreased blood flow to skin
Albinism—milky white skin and blue-gray eyes due to genetic lack of melanin synthesizing enzyme
Jaundice—yellowing due to bilirubin in blood (can be caused by compromised liver function)
Hematoma—bruising (clotted blood under skin
Define hair
A slender filament of keratinized cells growing from a tube in the skin called a hair follicle
What are the 3 sections of a hair along its length?
Bulb: Contains matrix cells (mitotically active cells)
Root: the remainder of the hair in the follicle
Shaft: the portion above the skin surface
What are the three layers of a hair visible in a cross-section?
Medulla (core), Cortex, Cuticle (outer layer)
Describe hair receptors
sensory nerve fibers entwining follicles
Detect hair movement
Describe the piloerector muscle (arrector pili)
Smooth muscle attaching follicle to dermis
Contracts to make hair stand on end (goose bumps)
What are the 4 main functions of hair?
Protection
Light touch
Heat retention
Excretion
Describe the composition of fingernails
They’re clear, hard derivatives of stratum corneum composed of thin, dead cells packed with hard keratin
Describe merocrine/eccrine sweat glands
Most numerous of skin glands
Duct opens to surface of skin
Regulates body temperature with perspiration
Describe apocrine sweat glands
Locations: groin, anal region, axilla, areola, beard (men)
Inactive until puberty; responds to stress and sexual stimulation
Ducts lead to nearby hair follicles
Believed to secrete pheromones
Define bromhidrosis
Disagreeable body odor produced by bacterial action on sweat from apocrine glands
Describe sebaceous glands
Most open into a hair follicle, and they utilize a holocrine secretion style to secrete sebum
Describe sebum
The oily secretion of sebaceous glands
Keeps skin and hair from becoming dry, brittle, and cracked
Inhibits growth of bacteria & fungi (ringworm)
Give an example of a modified oil gland
Ciliary Glands
Describe the ceruminous glands in external ear canal
Modified apocrine glands Forms earwax (cerumen)
Describe mammary glands
Milk-producing glands that develop only during pregnancy.
Modified apocrine sweat glands
Rich secretion released through ducts opening at nipple
What causes most skin cancers?
Most cases caused by UV rays of the sun damaging skin cell DNA
What are the three types of skin cancer? Describe their malignancy
1) Basal cell carcinoma Most common but least malignant 2) Squamous cell carcinoma May metastasize if not removed 3) Melanoma Least common but very malignant
Describe basal cell carcinomas
Most common type
Least dangerous because it seldom metastasizes
Forms from cells in stratum basale
Lesion is small, shiny bump with central depression and beaded edges
Describe squamous cell carcinoma
- Arises from keratinocytes of stratum spinosum
- Lesions usually on scalp, ears, lower lip, or back of the hand
- Have raised, reddened, scaly appearance later forming a concave ulcer
- Chance of recovery good with early detection and surgical removal
- Tends to metastasize to lymph nodes and may become lethal
Describe malignant melanoma
Skin cancer that arises from melanocytes
Less than 5% of skin cancers, but most deadly form
Can be successfully removed if caught early, but if it metastasizes it is usually fatal
Greatest risk factor: familial history of malignant melanoma
Highest incidence in men, redheads, and people who had severe sunburn as a child
List the ABCDEs of melanomas
A: Asymmetry B: Border C: Color D: Diameter E: Elevation and/or evolution
Describe burns
The leading cause of accidental death
Fires, kitchen spills, sunlight, ionizing radiation, strong acids or bases, or electrical shock
Deaths result primarily from fluid loss, infection, and toxic effects of eschar (burned, dead tissue)
Debridement: removal of eschar
Burns classified according to depth of tissue involvement
Describe first degree burns
Involves only epidermis; Heals in days
Describe second degree burns
Partial-thickness burn; involves part of dermis
May appear red, tan, or white; blistered and painful
Two weeks to several months to heal and may leave scars
Describe third degree burns
Full-thickness burn; involves epidermis, all of dermis, and often some deeper tissues
Often requires skin grafts
Needs fluid replacement, infection control, supplemental nutrition
The tissue found covering body surfaces, lining body cavities, forming the internal and external linings of many organs, and constituting most gland tissue is _____ tissue
epithelial
Which term is used to describe the free surface of an epithelium? Apical Basal Open Medullary
Apical
Which epithelium lines the respiratory tract from the nasal cavity to the bronchi? Simple cuboidal Transitional Simple columnar Pseudostratified columnar
Pseudostratified columnar
Which surface of an epithelial cell faces the basement membrane?
Basal
Apical
Basal
Which epithelium has tall columnar cells in a single layer interspersed with shorter basal cells and nuclei at varying levels? Stratified columnar Stratified squamous Pseudostratified columnar Simple cuboidal
Pseudostratified columnar
What is the function of transitional epithelium? To allow stretching To absorb nutrients To move fluid through tubules To protect against abrasion
To allow stretching
Which epithelium forms glandular epithelium and lines the kidney tubules? Simple cuboidal Pseudostratified columnar Stratified columnar Simple squamous
Simple cuboidal
Which epithelium is best suited for resisting abrasion and preventing pathogen entry into deeper tissues? Areolar Dense regular Stratified squamous Simple cuboidal
Stratified squamous
Which are functions of connective tissue in the body? (more than one correct answer) Absorption Support and protect organs Bind organs to one another Communication
Support and protect organs
Bind organs to one another
Which cells found in connective tissue engulf foreign particles, activate the immune system, and destroy dead or dying cells? Adipocytes Macrophages Reticulocytes Chondroblasts Fibroblasts
Macrophages
