mcq on Histology of Integumentary System

Instruction: pick the one best answer. This is also useful on the USMLE step 1.

1. Which of the following is composed of loose connective tissue?

a. Epidermis

b. Reticular layer of dermis

c. Hypodermis

d. Both a and b

e. Both b and c

Answer: c

The skin is composed of two layers: the epidermis and the dermis. Underneath these layers lies the hypodermis. The epidermis is stratified squamous epithelium. The dermis is composed of a papillary layer and a reticular layer. The reticular layer of the dermis is made up of dense irregular connective tissue. The hypodermis is a layer of loose connective tissue.

2. Where is thick skin found?

a. Over the knee

b. Sole of the feet

c. Breast

d. Lips

e. All of the above

Answer: b

3. Which layer of the epidermis has cells which have keratohyaline granules?

a. Stratum basale

b. Stratum spinosum

c. Stratum granulosum

d. Stratum lucidum

e. Stratum corneum

Answer: c

The epidermis is divided into five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

The stratum basale contains the dividing cells. This layer is also called the stratum germinativum.

The stratum spinosum consists of a layer several cells deep. The cells have pointy or spiny processes on them. The cells in the stratum granulosum contain keratohyaline granules.

The stratum lucidum is present only in thick skin.

The stratum corneum is the outermost layer. The cells in this layer are essentially bags of keratin. They contain no nuclei or organelles.

Histology hint from Sarah Bellham: My favorite mnemonic for remembering the layers of the skin: "Californian Ladies Give Superb Backrubs"

4. Which cell is a macrophage found in the skin?

a. Kupffer cells

b. Histiocyte

c. Dust cell

d. Langerhans cell

e. Microglia

Answer: d

Macrophages are mononuclear phagocytes. Many tissues have resident (fixed) macrophages. Fixed macrophages are given a unique name, depending on the tissue that they are located in. Kupffer cells are the hepatic macrophages. Histiocytes are macrophages seen in connective tissue. Dust cells are alveolar macrophage found in the respiratory tract. Langerhans cells are macrophages seen in the skin. Microglia are the central nervous system macrophages.

5. A new miracle skin cream recently hit the beauty counters which is suppose to stimulate collagen production. Which cell is it supposedly stimulating?

a. Langerhans cell

b. Keratinocyte

c. Melanocyte

d. Merkel cell

e. Fibroblast

Answer: e

Langerhans cells, keratinocytes, melanocytes, and Merkel cells are all found in the epidermis. The Langerhans cell is a phagocyte. The keratinocyte is the most abundant cell in the epidermis. The melanocyte produces melanin, which is responsible for skin pigmentation. The Merkel cell is a mechanoreceptor.

Fibroblasts are found in the dermis. Fibroblasts produces collagen.

6. What is the half moon shaped white area on a nail called?

a. Lunula

b. Eponychium

c. Matrix

d. Nail bed

e. Root

Answer: a

The lunula is the half moon shaped white area on a nail. The anatomical term for the cuticle is the eponychium. The matrix is the region of the nails where there are dividing cells and nail growth. The nail plate rests on the nail bed. The nail root is the proximal portion of the nail that is underneath skin.

7. What is the growing part of the nail?

a. Lunula

b. Eponychium

c. Matrix

d. Nail bed

e. Root

Answer: c

The lunula is the half moon shaped white area on a nail. The anatomical term for the cuticle is the eponychium. The matrix is the region of the nails where there are dividing cells and nail growth. The nail plate rests on the nail bed. The nail root is the proximal portion of the nail that is underneath skin.

8. What type of glands are the ceruminous glands?

a. Sebaceous glands

b. Eccrine sweat gland

c. Endocrine gland

d. Apocrine sweat gland

e. Oil gland

Answer: d

The ceruminous glands of the ear are apocrine sweat glands.

9. Which of the following is the most abundant sensory receptor of the skin?

a. Free nerve endings

b. Ruffini's corpuscles

c. Pacinian corpuscles

d. Krause's end bulbs

e. Meissner's corpuscle

Answer: a

There are several different sensory receptors in the skin. The most abundant sensory receptor are the free nerve endings. Free nerve endings respond to pain and temperature. Ruffini's corpuscles respond to continuous pressure. Pacinian corpuscles respond to vibration and rapidly changing pressure. Krause's end bulbs are a receptor for fine touch which are located in mucous membranes and the tongue. Meissner's corpuscles are also a receptor for fine touch but they are located in the dermis.

10. Where can hair be found?

a. Palms of hand

b. Soles of feet

c. Urogenital openings

d. Lips

e. Eyelid

Answer e

Hair is present over most of the body. It is not found on the palms of the hand, 

soles of the feet, urogenital openings, and lips.

11. Which of the following is composed of connective tissue?

a. Epidermis

b. Dermis

c. Hypodermis

d. Both a and b

e. Both b and c

Answer: e

The skin is composed of two layers: the epidermis and the dermis. Underneath these layers lies the hypodermis. The epidermis is stratified squamous epithelium. The dermis is composed of a papillary layer and a reticular layer. The reticular layer of the dermis is made up of dense irregular connective tissue. The hypodermis is a layer of loose connective tissue.

12. Which of the following is composed of dense irregular connective tissue?

a. Epidermis

b. Reticular layer of dermis

c. Hypodermis

d. Both a and b

e. Both b and c

Answer: b

The skin is composed of two layers: the epidermis and the dermis. Underneath these layers lies the hypodermis. The epidermis is stratified squamous epithelium. The dermis is composed of a papillary layer and a reticular layer. The reticular layer of the dermis is made up of dense irregular connective tissue. The hypodermis is a layer of loose connective tissue.

13. Where is thick skin found?

a. Lips

b. Over the knee

c. Palms

d. Breast

e. All of the above

Answer: c

Thick skin is found on the palms of the hand and the sole of the feet. Thin skin 

is found everywhere else.

14. Which layer of the epidermis is present only in thick skin?

a. Stratum basale

b. Stratum spinosum

c. Stratum granulosum

d. Stratum lucidum

e. Stratum corneum

Answer: d

The epidermis is divided into five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

The stratum basale contains the dividing cells. This layer is also called the stratum germinativum.

The stratum spinosum consists of a layer several cells deep. The cells have pointy or spiny processes on them. The cells in the stratum granulosum contain keratohyaline granules.

The stratum lucidum is present only in thick skin.

The stratum corneum is the outermost layer. The cells in this layer are essentially bags of keratin. They contain no nuclei or organelles.

Note from Sarah Bellham: My favorite mnemonic for remembering the layers of the skin: "Californian Ladies Give Superb Backrubs"

15. Which cell is a mechanoreceptors?

a. Langerhans cell

b. Keratinocyte

c. Melanocyte

d. Merkel cell

e. Fibroblast

Answer: d

Langerhans cells, keratinocytes, melanocytes, and Merkel cells are all found in the epidermis. The Langerhans cell is a phagocyte. The keratinocyte is the most abundant cell in the epidermis. The melanocyte produces melanin, which is responsible for skin pigmentation. The Merkel cell is a mechanoreceptor.

Fibroblasts are found in the dermis. Fibroblasts produces collagen.

16. Which cell is found in the dermis?

a. Langerhans cell

b. Keratinocyte

c. Melanocyte

d. Merkel cell

e. Fibroblast

Answer: e

Langerhans cells, keratinocytes, melanocytes, and Merkel cells are all found in the epidermis. The Langerhans cell is a phagocyte. The keratinocyte is the most abundant cell in the epidermis. The melanocyte produces melanin, which is responsible for skin pigmentation. The Merkel cell is a mechanoreceptor.

Fibroblasts are found in the dermis. Fibroblasts produces collagen.

17. What is underneath the nail plate?

a. Lunula

b. Eponychium

c. Matrix

d. Nail bed

e. Root

Answer: d

The lunula is the half moon shaped white area on a nail. The anatomical term for the cuticle is the eponychium. The matrix is the region of the nails where there are dividing cells and nail growth. The nail plate rests on the nail bed. The nail root is the proximal portion of the nail that is underneath skin.

18.What is the innervation of an eccrine sweat gland?

a. Cholinergic; parasympathetic

b. Cholinergic; sympathetic

c. Adrenergic; parasympathetic

d. Adrenergic; sympathetic

e. Cholinergic; motor

Answer: b

Eccrine sweat glands are innervated by the sympathetic nervous system. The neurotransmitter for the eccrine sweat glands is acetylcholine. Thus it is cholinergic.

Note from Sarah Bellham: For most postganglionic sympathetic neurons, the neurotransmitter is norepinephrine. Eccrine sweat glands are an exception to this generalization, as the innervation for eccrine sweat glands is cholinergic sympathetic.

19.Which of the following responds to continuous pressure?

a. Free nerve endings

b. Ruffini's corpuscles

c. Pacinian corpuscles

d. Krause's end bulbs

e. Meissner's corpuscle

Answer: b

There are several different sensory receptors in the skin. The most abundant sensory receptor are the free nerve endings. Free nerve endings respond to pain and temperature. Ruffini's corpuscles respond to continuous pressure. Pacinian corpuscles respond to vibration and rapidly changing pressure. Krause's end bulbs are a receptor for fine touch which are located in mucous membranes and the tongue. Meissner's corpuscles are also a receptor for fine touch but they are located in the dermis.

20. Which of the following is found in the hair follicle?

a. Pigment epithelium

b. Muller's cells

c. Huxley's layer

d. Horizontal cells

e. Cones

Answer: c

Pigment epithelium, Muller's cells, horizontal cells, and cones are all part of the retina.

Huxley's layer is a layer in the hair follicle.

21. The reticular layer is part of which layer?

a. Epidermis

b. Dermis

c. Hypodermis

d. Both a and b

e. None of the above

Answer: b

The skin is composed of two layers: the epidermis and the dermis. Underneath these layers lies the hypodermis. The epidermis is stratified squamous epithelium. The dermis is composed of a papillary layer and a reticular layer. The reticular layer of the dermis is made up of dense irregular connective tissue. The hypodermis is a layer of loose connective tissue.

22. Which of the following is NOT considered an epidermal appendage?

a. Sweat gland

b. Hair

c. Hypodermis

d. Nails

e. Sebaceous glands

Answer: c

Sweat glands, hair, nails and sebaceous glands are all considered epidermal appendages. The hypodermis is not considered an epidermal appendage. The hypodermis is the loose connective tissue layer underneath the dermis.

23. Which layer of the epidermis is also called the stratum germinativum?

a. Stratum basale

b. Stratum spinosum

c. Stratum granulosum

d. Stratum lucidum

e. Stratum corneum

Answer: a

The epidermis is divided into five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

The stratum basale contains the dividing cells. This layer is also called the stratum germinativum.

The stratum spinosum consists of a layer several cells deep. The cells have pointy or spiny processes on them. The cells in the stratum granulosum contain keratohyaline granules.

The stratum lucidum is present only in thick skin.

The stratum corneum is the outermost layer. The cells in this layer are essentially bags of keratin. They contain no nuclei or organelles.

Note from Sarah Bellham: My favorite mnemonic for remembering the layers of the skin: "Californian Ladies Give Superb Backrubs"

24. Which layer of the epidermis is on the surface of the skin?

a. Stratum basale

b. Stratum spinosum

c. Stratum granulosum

d. Stratum lucidum

e. Stratum corneum

Answer: e

The epidermis is divided into five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

The stratum basale contains the dividing cells. This layer is also called the stratum germinativum.

The stratum spinosum consists of a layer several cells deep. The cells have pointy or spiny processes on them. The cells in the stratum granulosum contain keratohyaline granules.

The stratum lucidum is present only in thick skin.

The stratum corneum is the outermost layer. The cells in this layer are essentially bags of keratin. They contain no nuclei or organelles.

Note from Sarah Bellham: My favorite mnemonic for remembering the layers of the skin: "Californian Ladies Give Superb Backrubs"

25. Which cell is the most abundant cell in the epidermis?

a. Langerhans cell

b. Keratinocyte

c. Melanocyte

d. Merkel cell

e. Fibroblast

Answer: b

Langerhans cells, keratinocytes, melanocytes, and Merkel cells are all found in the epidermis. The Langerhans cell is a phagocyte. The keratinocyte is the most abundant cell in the epidermis. The melanocyte produces melanin, which is responsible for skin pigmentation. The Merkel cell is a mechanoreceptor.

Fibroblasts are found in the dermis. Fibroblasts produces collagen.

26. What type of epithelium forms the epidermis?

a. Simple squamous epithelium

b. Simple cuboidal epithelium

c. Simple columnar epithelium

d. Stratified squamous epithelium

e. Pseudostratified epithelium

Answer: d

The epidermis is formed by stratified squamous epithelium. Epithelium lines body cavities and surfaces. Stratified squamous epithelium is "stratified" because it is more than one cell layer thick. "Squamous" refers to the fact that the surface cells of the stratified squamous layer are flat. This is important to note as the cells at the basal layer are cuboidal or even columnar. It is still classified as "squamous" based on the cells of the surface layer.

27. What is the portion of the nail which is underneath skin?

a. Lunula

b. Eponychium

c. Matrix

d. Nail bed

e. Root

Answer: e

The lunula is the half moon shaped white area on a nail. The anatomical term for the cuticle is the eponychium. The matrix is the region of the nails where there are dividing cells and nail growth. The nail plate rests on the nail bed. The nail root is the proximal portion of the nail that is underneath skin.

28. What type of glands are the glands of Moll?

a. Endocrine gland

b. Apocrine sweat gland

c. Oil gland

d. Sebaceous glands

e. Eccrine sweat gland

Answer: b

The glands of Moll in the eyelid are apocrine sweat glands.

29. Which of the following responds to vibration and rapidly changing pressure?

a. Free nerve endings

b. Ruffini's corpuscles

c. Pacinian corpuscles

d. Krause's end bulbs

e. Meissner's corpuscle

Answer: c

There are several different sensory receptors in the skin. The most abundant sensory receptor are the free nerve endings. Free nerve endings respond to pain and temperature. Ruffini's corpuscles respond to continuous pressure. Pacinian corpuscles respond to vibration and rapidly changing pressure. Krause's end bulbs are a receptor for fine touch which are located in mucous membranes and the tongue. Meissner's corpuscles are also a receptor for fine touch but they are located in the dermis.

30. Which of the following is a receptor for fine touch which is located in mucous membranes?

a. Free nerve endings

b. Ruffini's corpuscles

c. Pacinian corpuscles

d. Krause's end bulbs

e. Meissner's corpuscle

Answer: d

There are several different sensory receptors in the skin. The most abundant sensory receptor are the free nerve endings. Free nerve endings respond to pain and temperature. Ruffini's corpuscles respond to continuous pressure. Pacinian corpuscles respond to vibration and rapidly changing pressure. Krause's end bulbs are a receptor for fine touch which are located in mucous membranes and the tongue. Meissner's corpuscles are also a receptor for fine touch but they are located in the dermis.

31. Which of the following is composed of stratified squamous epithelium?

a. Epidermis

b. Dermis

c. Hypodermis

d. Both a and b

e. Both b and c

Answer: a

The skin is composed of two layers: the epidermis and the dermis. Underneath these layers lies the hypodermis. The epidermis is stratified squamous epithelium. The dermis is composed of a papillary layer and a reticular layer. The reticular layer of the dermis is made up of dense irregular connective tissue. The hypodermis is a layer of loose connective tissue.

32. Which of the following is NOT a function of skin

a. Vitamin D production

b. Protection from water loss

c. Sensory reception

d. Heat regulation

e. All are functions of skin

Answer: e

The skin is involved in the production of vitamin D from precursors with the aid of the sun. It protects the body from water loss. There are many sensory receptors in the skin: pain, pressure, fine touch. The skin is also involved in heat regulation. In addition, the skin protects the body.

33. Which layer of the epidermis contains dividing cells?

a. Stratum basale

b. Stratum spinosum

c. Stratum granulosum

d. Stratum lucidum

e. Stratum corneum

Answer: a

The epidermis is divided into five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

The stratum basale contains the dividing cells. This layer is also called the stratum germinativum.

The stratum spinosum consists of a layer several cells deep. The cells have pointy or spiny processes on them. The cells in the stratum granulosum contain keratohyaline granules.

The stratum lucidum is present only in thick skin.

The stratum corneum is the outermost layer. The cells in this layer are essentially bags of keratin. They contain no nuclei or organelles.

Note from Sarah Bellham: My favorite mnemonic for remembering the layers of the skin: "Californian Ladies Give Superb Backrubs"

34. Which layer of the epidermis contains cells with no nuclei or organelles?

a. Stratum basale

b. Stratum spinosum

c. Stratum granulosum

d. Stratum lucidum

e. Stratum corneum

Answer: e

The epidermis is divided into five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

The stratum basale contains the dividing cells. This layer is also called the stratum germinativum.

The stratum spinosum consists of a layer several cells deep. The cells have pointy or spiny processes on them. The cells in the stratum granulosum contain keratohyaline granules.

The stratum lucidum is present only in thick skin.

The stratum corneum is the outermost layer. The cells in this layer are essentially bags of keratin. They contain no nuclei or organelles.

Note from Sarah Bellham: My favorite mnemonic for remembering the layers of the skin: "Californian Ladies Give Superb Backrubs"

35. Which cell is a phagocyte?

a. Langerhans cell

b. Keratinocyte

c. Melanocyte

d. Merkel cell

e. Fibroblast

Answer: a

Langerhans cells, keratinocytes, melanocytes, and Merkel cells are all found in the epidermis. The Langerhans cell is a phagocyte. The keratinocyte is the most abundant cell in the epidermis. The melanocyte produces melanin, which is responsible for skin pigmentation. The Merkel cell is a mechanoreceptor.

Fibroblasts are found in the dermis. Fibroblasts produces collagen.

36. What is a characteristic of the cells in the epidermis of the skin?

a. Microvilli

b. Stereocilia

c. Cilia

d. Keratinization

e. Both a and b

Answer: d

Microvilli are the finger like projections seen on the surface of some cells. The appearance of microvilli form what is also called the brush border or striated border.

Stereocilia are very long microvilli. Stereocilia are seen in the epididymis and the hair cells of the ear.

Cilia is the hair like surface modification seen on some epithelia. Cilia are made of microtubules.

Keratinization is seen in the epidermis. Cells in the stratum corneum are essentially just bags of keratin.

37. Where are apocrine sweat glands NOT found?

a. Areola

b. External genitalia

c. Posterior neck

d. Axilla

e. Circumanal region

Answer: c

Sweat glands are divided into apocrine and eccrine. Apocrine sweat glands are found on the areola, external genitalia, axilla, and curcumanal region. Eccrine sweat glands are distributed over most of the body.

38. What is the innervation of an apocrine sweat gland?

a. Cholinergic; parasympathetic

b. Cholinergic; sympathetic

c. Adrenergic; parasympathetic

d. Adrenergic; sympathetic

e. Cholinergic; motor

Answer: d

Apocrine sweat glands are innervated by the sympathetic nervous system. The neurotransmitter for the apocrine sweat glands is norepinephrine. Thus it is adrenergic.

39. Which of the following is a receptor for fine touch which is located in the dermis?

a. Free nerve endings

b. Ruffini's corpuscles

c. Pacinian corpuscles

d. Krause's end bulbs

e. Meissner's corpuscle

Answer: e

There are several different sensory receptors in the skin. The most abundant sensory receptor are the free nerve endings. Free nerve endings respond to pain and temperature. Ruffini's corpuscles respond to continuous pressure. Pacinian corpuscles respond to vibration and rapidly changing pressure. Krause's end bulbs are a receptor for fine touch which are located in mucous membranes and the tongue. Meissner's corpuscles are also a receptor for fine touch but they are located in the dermis.

40. Which of the following is found in the hair follicle?

a. Henle's layer

b. Bipolar cells

c. Amacrine cells

d. Rods

e. Ganglion cells

Answer: a

Bipolar cells, amacrine cells, rods, and ganglion cells are all part of the retina.

Henle's layer is a layer in the hair follicle.

41. The papillary layer is part of which layer?

a. Epidermis

b. Dermis

c. Hypodermis

d. Both a and b

e. None of the above

Answer: b

The skin is composed of two layers: the epidermis and the dermis. Underneath these layers lies the hypodermis. The epidermis is stratified squamous epithelium. The dermis is composed of a papillary layer and a reticular layer. The reticular layer of the dermis is made up of dense irregular connective tissue. The hypodermis is a layer of loose connective tissue.

42. Which layer of the epidermis contains star shaped cells?

a. Stratum basale

b. Stratum spinosum

c. Stratum granulosum

d. Stratum lucidum

e. Stratum corneum

Answer: b

The epidermis is divided into five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

The stratum basale contains the dividing cells. This layer is also called the stratum germinativum.

The stratum spinosum consists of a layer several cells deep. The cells have pointy or spiny processes on them. The cells in the stratum granulosum contain keratohyaline granules.

The stratum lucidum is present only in thick skin.

The stratum corneum is the outermost layer. The cells in this layer are essentially bags of keratin. They contain no nuclei or organelles.

Note from Sarah Bellham: My favorite mnemonic for remembering the layers of the skin: "Californian Ladies Give Superb Backrubs"

43. Which of the following layers comprise the skin?

a. Epidermis

b. Dermis

c. Hypodermis

d. Both a and b

e. Both b and c

Answer: d

The skin is composed of two layers: the epidermis and the dermis. Underneath these layers lies the hypodermis. The epidermis is stratified squamous epithelium. The dermis is composed of a papillary layer and a reticular layer. The reticular layer of the dermis is made up of dense irregular connective tissue. The hypodermis is a layer of loose connective tissue.

44. Which cell is responsible for skin pigmentation?

a. Langerhans cell

b. Keratinocyte

c. Melanocyte

d. Merkel cell

e. Fibroblast

Answer: c

Langerhans cells, keratinocytes, melanocytes, and Merkel cells are all found in the epidermis. The Langerhans cell is a phagocyte. The keratinocyte is the most abundant cell in the epidermis. The melanocyte produces melanin, which is responsible for skin pigmentation. The Merkel cell is a mechanoreceptor.

Fibroblasts are found in the dermis. Fibroblasts produces collagen.

45. Which of the following responds to pain?

a. Free nerve endings

b. Ruffini's corpuscles

c. Pacinian corpuscles

d. Krause's end bulbs

e. Meissner's corpuscle

Answer: a

There are several different sensory receptors in the skin. The most abundant sensory receptor are the free nerve endings. Free nerve endings respond to pain and temperature. Ruffini's corpuscles respond to continuous pressure. Pacinian corpuscles respond to vibration and rapidly changing pressure. Krause's end bulbs are a receptor for fine touch which are located in mucous membranes and the tongue. Meissner's corpuscles are also a receptor for fine touch but they are located in the dermis.

46. What is the correct term for cuticle?

a. Lunula

b. Eponychium

c. Matrix

d. Nail bed

e. Root

Answer: b

The lunula is the half moon shaped white area on a nail. The anatomical term for the cuticle is the eponychium. The matrix is the region of the nails where there are dividing cells and nail growth. The nail plate rests on the nail bed. The nail root is the proximal portion of the nail that is underneath skin.

47. What color is keratin with Masson's trichrome stain?

a. Red

b. Pink

c. Green

d. Black

e. Yellow

Answer: a

A trichrome stain is a mixture of three dyes. Collagen fibers stain green with Masson's trichrome stain. Muscle and keratin will be red with Masson's trichrome stain. Cytoplasm will be pink. Nuclei will be black.

48. What type of tissue makes up the dermis of the skin?

a. Mucous connective tissue

b. Mesenchyme

c. Loose irregular connective tissue

d. Dense irregular connective tissue

e. Dense regular connective tissue

Answer: d

Mesenchyme is embryonic connective tissue. It is an undifferentiated tissue found in the embryo. Mucous connective tissue is a type of embryonic connective tissue; it is a subset of mesenchyme. Wharton's jelly is mucous connective tissue. Loose irregular connective tissue is areolar tissue. Dense irregular connective tissue is seen in the dermis. Dense regular connective tissue comprises tendons and ligaments.

49.What are the pressure receptors in skin called?

a. Psammoma bodies

b. Corpora arenacea

c. Hassall's corpuscles

d. Prostatic concretions

e. Pacinian corpuscles

Answer: e

Psammoma bodies are collections of calcium. It is derived from the Greek word "psammos", which means sand.

Corpora arenacea refers to the calcifications seen in the pineal gland. Corpora arenacea is nicknamed "brain sand".

Hassall's corpuscles are the ring like structures found in the thymus.

The spherical structures seen in some prostatic alveoli are called prostatic concretions.

Pacinian corpuscles are pressure receptors in the skin.

50. Which sensory receptor in the skin is NOT encapsulated?

a. Ruffini endings

b. Free nerve endings

c. Pacinian corpuscles

d. Meissner's corpuscles

e. Merkel cells

Answer: b

Ruffini endings, pacinian corpuscles, meissner's corpuscles, and merkel cells are all encapsulated sensory receptors. Free nerve endings are not encapsulated.