BIO 168 Midterm Exam Questions and Answers With Verified Solutions 2025
Skin layers from top to bottom - ✔✔Stratum corneum, Stratum lucidem, Stratum granulosum, Stratum
spinosum, Stratum basale
Epidermis (surface) - ✔✔keratinized, stratified squamous epithelium, made of keratinocytes - produce
fibrous protein keratin and also made of melanocytes that produce melanin, epidermal dendritic cells
(Langerhans) and tactile cells (Merkel)
Dermis (middle) - ✔✔strong, flexible connective tissue that is made mostly of fibroblasts and
macrophages as well as occasionally mast cells and WBCs, 2 layers - thin papillary layer (vascular) and
thicker reticular layer (strength)
Hypodermis (deep) - ✔✔subcutaneous layer, mostly adipose tissue
What gives us our skin color? - ✔✔melanin - yellow to reddish-brown to black pigments give diversity to
skin colors
What are the four appendages of the skin? - ✔✔hairs and hair follicles, nails, sweat glands and oil glands
What is the function of the hair appendage? - ✔✔alerting the body to the presence of insects on skin,
guarding scalp against trauma, heat loss and sunlight
What is the function of the nails appendage? - ✔✔protect the end of fingers/toes from injury, allow
ability to pick up objects, support tips
What is the function of the sweat glands appendage? - ✔✔apocrine - sexually stimulated scent glands,
eccrine - most common sweat gland, thermoregulation, mammary glands in females secrete milk
(modified apocrine)
What are the functions of skin? - ✔✔Protection, body temperature regulation, cutaneous sensation,
metabolic functions, blood reservoir, excretion
Basal cell carcinoma - ✔✔stratum basale cells proliferate and slowly invade dermis and hypodermis,
least malignant, most common
Squamus cell carcinoma - ✔✔keratinocytes of stratum spinosum proliferate forming lesions most often
on head
Melanoma - ✔✔melanocytes proliferate and rapidly metastasize, most dangerous
What is the ABCD rule? - ✔✔asymmetry, border irregularity, color, diameter
What are the two big concerns with burns? - ✔✔immediate threat (dehydration and electrolyte
imbalance leading to renal shutdown and circulatory shock) and the farther threat (infection of the area)
What is the rule of nines? - ✔✔each upper limb = 9%
each lower limb = 18%
, anterior and posterior trunk = 18% each
head and neck = 9%
perineum and genitalia = 1%
How do we determine if a burn is critical? - ✔✔>25% of the body has 2nd degree burns, >10% of the
body has 3rd degree burns, face/hands/feet bear 3rd degree burns (face can lead to damage to airways)
What are the two types of bone tissue and what are they made of? - ✔✔compact bone made of osteons
and spongy bone made of trabeculae
Osteon diagram - ✔✔Twisting force of lamellae add strength (twister resister)
What are the 3 skeletal cartilages? - ✔✔hyaline, elastic, fibrocartilage
Hyaline cartilage - ✔✔Provides support, flexibility, and resilience, collagen fibers only; most abundant
type, articular (joint), costal, respiratory, nasal cartilage
Elastic cartilage - ✔✔contains elastic fibers, external ear and epiglottis
Fibrocartilage - ✔✔cartilage that contains fibrous bundles of collagen, such as that of the intervertebral
disks in the spinal cord, have great tensile strength, act as shock absorbers between vertebrae
How are bones classified? - ✔✔by location - axial (trunk) skeleton and appendicular (limbs) skeleton and
by shape - long bones, short (cube) bones, flat bones, irregular complicated bones
Long bone diagram - ✔✔
What are the four bone cells? - ✔✔osteogenic, osteoblasts, osteocytes, osteoclasts
Osteogenic cells - ✔✔stem cells that differentiate into osteoblasts
Osteoblast cells - ✔✔secrete the organic matrix of bone and osteocytes are housed in lacunae, similar to
chondrocyte cells
Osteocyte cells - ✔✔mature bone cell (located in lacunae)
Osteoclast cells - ✔✔break down bone matrix and resorb the minerals
Intramembranous ossification - ✔✔membrane bone develops from fibrous membrane, forms flat bones
ex: clavicles and cranial bones
Endochondrial ossification - ✔✔cartilage bone forms by replacing hyaline cartilage, forms most of the
rest of the skeleton
What are the stages of growth in a long bone? - ✔✔fetal endochondrial ossification - 1. bone collar
forms around the diaphysis 2. cartilage calcifies in the center of the diaphysis and then develops cavities
3. the periosteal bud invades the internal cavities and spongy bone forms 4. the diaphysis elongates and
a medullary cavity forms, secondary ossification centers appear in the epiphyses 5. the epiphyses ossify,
when ossification is complete, hyaline cartilage remains only in the epiphyseal plates and the articular
cartilages
Skin layers from top to bottom - ✔✔Stratum corneum, Stratum lucidem, Stratum granulosum, Stratum
spinosum, Stratum basale
Epidermis (surface) - ✔✔keratinized, stratified squamous epithelium, made of keratinocytes - produce
fibrous protein keratin and also made of melanocytes that produce melanin, epidermal dendritic cells
(Langerhans) and tactile cells (Merkel)
Dermis (middle) - ✔✔strong, flexible connective tissue that is made mostly of fibroblasts and
macrophages as well as occasionally mast cells and WBCs, 2 layers - thin papillary layer (vascular) and
thicker reticular layer (strength)
Hypodermis (deep) - ✔✔subcutaneous layer, mostly adipose tissue
What gives us our skin color? - ✔✔melanin - yellow to reddish-brown to black pigments give diversity to
skin colors
What are the four appendages of the skin? - ✔✔hairs and hair follicles, nails, sweat glands and oil glands
What is the function of the hair appendage? - ✔✔alerting the body to the presence of insects on skin,
guarding scalp against trauma, heat loss and sunlight
What is the function of the nails appendage? - ✔✔protect the end of fingers/toes from injury, allow
ability to pick up objects, support tips
What is the function of the sweat glands appendage? - ✔✔apocrine - sexually stimulated scent glands,
eccrine - most common sweat gland, thermoregulation, mammary glands in females secrete milk
(modified apocrine)
What are the functions of skin? - ✔✔Protection, body temperature regulation, cutaneous sensation,
metabolic functions, blood reservoir, excretion
Basal cell carcinoma - ✔✔stratum basale cells proliferate and slowly invade dermis and hypodermis,
least malignant, most common
Squamus cell carcinoma - ✔✔keratinocytes of stratum spinosum proliferate forming lesions most often
on head
Melanoma - ✔✔melanocytes proliferate and rapidly metastasize, most dangerous
What is the ABCD rule? - ✔✔asymmetry, border irregularity, color, diameter
What are the two big concerns with burns? - ✔✔immediate threat (dehydration and electrolyte
imbalance leading to renal shutdown and circulatory shock) and the farther threat (infection of the area)
What is the rule of nines? - ✔✔each upper limb = 9%
each lower limb = 18%
, anterior and posterior trunk = 18% each
head and neck = 9%
perineum and genitalia = 1%
How do we determine if a burn is critical? - ✔✔>25% of the body has 2nd degree burns, >10% of the
body has 3rd degree burns, face/hands/feet bear 3rd degree burns (face can lead to damage to airways)
What are the two types of bone tissue and what are they made of? - ✔✔compact bone made of osteons
and spongy bone made of trabeculae
Osteon diagram - ✔✔Twisting force of lamellae add strength (twister resister)
What are the 3 skeletal cartilages? - ✔✔hyaline, elastic, fibrocartilage
Hyaline cartilage - ✔✔Provides support, flexibility, and resilience, collagen fibers only; most abundant
type, articular (joint), costal, respiratory, nasal cartilage
Elastic cartilage - ✔✔contains elastic fibers, external ear and epiglottis
Fibrocartilage - ✔✔cartilage that contains fibrous bundles of collagen, such as that of the intervertebral
disks in the spinal cord, have great tensile strength, act as shock absorbers between vertebrae
How are bones classified? - ✔✔by location - axial (trunk) skeleton and appendicular (limbs) skeleton and
by shape - long bones, short (cube) bones, flat bones, irregular complicated bones
Long bone diagram - ✔✔
What are the four bone cells? - ✔✔osteogenic, osteoblasts, osteocytes, osteoclasts
Osteogenic cells - ✔✔stem cells that differentiate into osteoblasts
Osteoblast cells - ✔✔secrete the organic matrix of bone and osteocytes are housed in lacunae, similar to
chondrocyte cells
Osteocyte cells - ✔✔mature bone cell (located in lacunae)
Osteoclast cells - ✔✔break down bone matrix and resorb the minerals
Intramembranous ossification - ✔✔membrane bone develops from fibrous membrane, forms flat bones
ex: clavicles and cranial bones
Endochondrial ossification - ✔✔cartilage bone forms by replacing hyaline cartilage, forms most of the
rest of the skeleton
What are the stages of growth in a long bone? - ✔✔fetal endochondrial ossification - 1. bone collar
forms around the diaphysis 2. cartilage calcifies in the center of the diaphysis and then develops cavities
3. the periosteal bud invades the internal cavities and spongy bone forms 4. the diaphysis elongates and
a medullary cavity forms, secondary ossification centers appear in the epiphyses 5. the epiphyses ossify,
when ossification is complete, hyaline cartilage remains only in the epiphyseal plates and the articular
cartilages
