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Biomedicine I > 10. Integumentary and Lymphatic System > Flashcards

10. Integumentary and Lymphatic System Flashcards

1
Q

Skin Structure

A
  • The skin forms the integumentary system.
  • It is the largest organ of the human body.
  • 2 square metres (men), 0.5mm-4mm thickness.
  • Covers external body and continuous with mucous membranes internally.
  • An epithelial membrane -cutaneous membrane.
  • Contains accessory structures: glands, hair and nails.
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2
Q

Skin layers

A

Epidermis: The superficial layer of skin, formed of epithelial tissue (tightly packed cells).
Dermis: The middle layer of skin, formed of connective tissue. Also contains accessory structures such as sweat glands, hairs and sebaceous glands.
Subcutaneous / adipose layer:

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3
Q

Epidermis

A

• The epidermis is the superficial layer of skin.
• Formed of ‘keratinised epithelium’ (protective and waterproofing).
• The epidermis varies in thickness over the body.
• Interstitial fluid (situated in between cells) provides oxygen & nutrients to cells.
• The epidermis is drained by lymph.
• No blood vessels (avascular) and no nerve endings.
Complete replacement of epidermis occurs in approximately 40 days.

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4
Q

Epidermis Cells

A

90% of epidermal cells are Keratinocytes:
• Keratin is a tough fibrous protein that protects from heat, microbes & chemicals.
8% of epidermal cells are Melanocytes:
• Melanin is a pigment that contributes to skin colour and absorbs UV light.
• Melanin surrounds the nuclei of keratinocytes on the side towards skin surface.
• Two types of melanin in skin = Eumelanin(brown/black) & Pheomelanin(reddish/yellow).
2% of epidermal cells are Langerhans cells:
• Immune cells that are in involved in skin ‘surveillance’.

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5
Q

Epidermis Layers

A 
5 Layers
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
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6
Q

Stratum Corneum

A

25-30 layers of flattened dead keratinocytes.
•Cytoplasm replaced by keratin.
•Are shed (desquamated).

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7
Q

Stratum Lucidum

A
  • 3-5 layers of dead cells.

* Only present in thick skin.

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8
Q

Stratum Granulosum

A

• 3-5 layers of cells undergoing apoptosis

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9
Q

Stratum Spinosum

A

• 8-10 layers of new keratinocytes

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10
Q

Stratum Basale

A

•Single row dividing to form new keratinocytes.

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11
Q

Dermis

A

The thickest layer in skin, formed of connective tissue. The dermis contains a matrix of collagen and elastic fibres.
• Collagen fibres give tensile strength and elastic fibres allow skin to stretch & recoil.
The dermis also contains:
• Arterioles & capillaries (thermoregulation).
• Lymph vessels &sensory nerve endings.
• Sweat glands (and ducts), hairs& arrector pili muscles, sebaceous glands.
• Fibroblasts and immune cells –macrophages & mast cells.

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12
Q

Sweat (Sudoriferous) Glands

A
  • Most numerous in the palms, soles of feet, axillae & groin.
  • Consists of a gland, duct & pore. Located next to a capillary (receive secretions).
  • Excretion of urea (waste). Excessive sweating leads to dehydration and sodium (Na+) depletion.
  • Smell created by action of bacteria breaking down substances present in sweat such as fatty acids.
  • Body heat used to evaporate sweat –help regulate body temperature.
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13
Q

Sensory Nerve Endings

A
  • Meissner’s corpuscle: Sensitive to light pressure.
  • Pacinian corpuscle: Sensitive to deep pressure.
  • Free nerve ending: Sensitive to pain & temperature. 1cm square skin = 200 pain receptors
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14
Q

Dermis: Hairs

A
  • Hairs are concentric columns of dead keratinised cells bonded together by proteins.
  • Hair colour is genetically determined. Hormones influence distribution. Hair contains melanin pigments (more = darker).
  • A microscopic band of smooth muscle called ‘arrector pili’ connect the hair follicle to the dermis.
  • When the hair is erect, it traps a layer of air next to the skin (part of thermoregulation).
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15
Q

Dermis: Sebaceous Glands

A
  • Sebaceous glands secrete sebum which keeps hair soft, provides water-proofing for the skin and is anti-microbial.
  • Mostly located on the face, scalp, lip, eye lid, nipples, labial folds, glans penis.
  • Activity increases in puberty, decreasing with age.
  • The fatty acids in sebum inhibit bacterial growth.
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16
Q

Skin Functions

A
  • Protection
  • Thermoregulation (body temperature)
  • Vitamin D production
  • Sensation
  • Absorption
  • Excretion
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17
Q

Skin Functions: Protection

A

• Protection against dehydrationand external factors such as chemicals, toxins, trauma, light and microbes.

  1. Physical barrier -closely packed keratinised cells and melanin.
  2. Sebum-contains fatty acids which inhibit microbial growth.
  3. Sweat-contains lysozymes, which are enzymes that break down bacteria.
  4. Desquamation-shedding of skin cells helps remove microbes.
  5. Nerve sensors -induce protective reflexes.
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18
Q

Skin Functions: Thermoregulation

A

• Normal body temperature is 36.5 –37.5°C (98–100°F).
• Changes in the evening, during ovulation & exercise.
• Temperature control centres are the hypothalamus & medulla oblongata (brain stem).
Temperature regulation by the skin occurs via:
1. Activity of sweat glands (water evaporates off skin).
2. Activity of blood vessels (vasodilatation/vasoconstriction).
High body temperature -> vasodilation of peripheral blood vessels to promote heat loss
Low body temperature -> vasoconstriction of peripheral blood vessels to prevent heat loss

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19
Q

Hypothermia

A

<35oC
When core temperature drops below that required for normal metabolism & body functions
Death usually below 25oC

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20
Q

Hyperthermia

A

> 38.5°C
When core temperature elevatesabove 38.5oC
40oC -life threatening. 41oC -brain death. 45oC –death.

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21
Q

Vitamin D Formation

A
  • UV light activates a vitamin D precursor in the skin.
  • The kidneys convert the precursor to calcitriol.
  • Calcitriol acts as a hormone to increase uptake of calcium and phosphorus from food into blood, thus, ultimately supporting bone density.
  • Vitamin D is stored in the liver.
22
Q

Absorption

A 
Lipid-soluble molecules:
• VitA, D, E, K.
• Some medications.
• Essential oils.
• O2 and CO2.
Toxins:
• Acetone, carbon tetrachloride, lead and mercury, arsenic, poison oak and ivy
23
Q

Excretion

A
  • Salt (sodium chloride).
  • Water.
  • Urea.
  • Ammonia.
24
Q

Superficial Wound Healing

A
  • Includes abrasions and burns.
  • Basal cells move across the gap until contact inhibition occurs.
  • Epidermal growth factor causes multiplication of the basal cells until space is filled.
25
Q

Deep Wound Healing

A 
Deep wound: affects dermis and subcutaneous layer.
Phases: 
Inflammatory Phase
Proliferative Phase
Remodelling Phase
26
Q

Inflammatory Phase

A
  • Migration of leukocytes to clean up any microbes & foreign tissue.
  • Blood clot forms & becomes a scab. Epithelial cells migrate to repair the basement membrane.
27
Q

Proliferative Phase

A
  • Granulation tissue is formed with the laying of collagen & blood vessels.
  • Extensive growth & repair of epithelial cells.
28
Q

Remodelling Phase

A
  • Can take 3 weeks to 6 months.

* Scab sloughs off and scar tissue remains (fibrosis).

29
Q

Scar Tissue

A
  • A mark left on the skin or other body tissues where a wound, burn or sore has not healed completely and fibrous connective tissue has developed.
  • Contains denser collagen fibres, fewer hairs, glands, nerve endings and blood vessels (hence whiter).
30
Q

Types of Scar Tissue

A

Hypertrophic

Keloid

31
Q

Hypertrophic Scar

A

Stays within in the boundary of the wound

32
Q

Keloid Scar

A

Takes up a larger space than the wound (normally raised)

33
Q

The Lymphatic System

A
  • The lymphatic system is closely allied to the cardiovascular & immune system.
  • The lymphatic system consists of thin-walled vessels that transport fluid throughout the body, resembling veins.
  • Lymph travels from lymphatic capillaries, which unite to form larger lymphatic vessels.
  • Lymphatic vessels ultimately drain into the thoracic duct or the right lymphatic duct.
34
Q

The Lymphatic System: Functions

A
  1. Return proteins, lipids and water from the interstitial fluid to the blood.
  2. Immunity against harmful organisms.
35
Q

The Lymphatic System: Components

A
  • Lymph fluid (lymph)
  • Lymph vessels
  • Lymph nodes
  • Lymph organs (spleen & thymus)
  • Lymphoid tissue (e.g. tonsils)
  • Bone marrow
36
Q

Lymph

A
  • Lymph is a watery fluid similar to blood plasma but with less plasma proteins.
  • Same composition as interstitial fluid, which is found between cells & lymph is in lymphatic vessels, tissues & between organs
37
Q

Lymph Components

A
  • Water.
  • Leukocytes.
  • Plasma proteins (seeped out of capillaries).
  • Fats absorbed from the small intestine.
  • Bacteria and cell debris from damaged tissue.
38
Q

Lymphatic Vessels

A 
CAPILLARIES:
• Located in spaces between cells.
• Blind end tubes -one way structure.
• Recall: lacteal is a blind ended lymph vessel in the small intestine.
LARGER LYMPH VESSELS:
• Have 3 layers like veins.
• Numerous cup shaped valves.
• Vessels unite to form lymph trunks.
39
Q

Lymphatic vs. Cardiovascular System

A
  • The cardiovascular system is a circular and closed system in which the fluid (blood) leaves from and returns to the heart.
  • In comparison, the lymphatic system is a linear system in which the lymphatic capillaries at the peripheral tissues drain lymphatic fluid.
  • Lymphatic fluid contains cells, proteins and macromolecules and transports it back to the vascular system.
40
Q

Lymphatic Nodes

A
  • Lymph nodes filter lymph and remove foreign matter such as microbes, cell debris and tumour cells.
  • Lymph passes through many lymph nodes before returning to the blood.
  • 600 Bean shaped structures located in groups along lymph vessels throughout the body.
  • Generally follow same route as veins.
  • Filled with immune cells (lymphocytes & phagocytes).
41
Q

Lymphatic Nodes: Process

A
  • Lymph enters via afferent vessels.
  • Foreign substances are trapped in irregular channels by reticular fibres.
  • Macrophages destroy foreign substances by phagocytosis.
  • Whilst lymphocytes destroy remainder by immune response.
  • Filtered lymph leaves via efferent vessels.
  • Many afferent vessels, very few efferent. This slows down the flow of lymph.
42
Q

Lymph Nodes: Location and Function

A
  • 5 locations contain many: Cervical, axillary, inguinal, vertebral column, mesenteric (intestinal).
  • Lymph nodes develop during childhood; atrophy begins in adolescence.
  • Material not filtered passes on to the next node so by the time the lymph returns to the blood it should be ‘clean’.
  • During the early stages of infection, incomplete phagocytosis of microbes can cause swelling of the lymph nodes –lymphadenopathy.
43
Q

Spleen

A
  • The largest lymph organ –same size as heart.
  • Between the stomach and diaphragm on the left.
  • Similar in shape & structure to lymph nodes.
  • Contains white pulp and red pulp:
  • White pulp contains lymphocytes & macrophages.
  • Red pulp contains all the components of circulating blood.
44
Q

Spleen: Functions

A
  1. Haematopoesisin foetus.
  2. Blood reservoir.
  3. Phagocytosis of worn out of defective erythrocytes.
  4. Immunity: matures T & B lymphocytes.
45
Q

Spleen Rupture

A
  • Spleen rupture can occur following trauma.
  • Damage to the thin-walled veins (sinuses) can cause significant haemorrhage and shock.
  • Removal is needed to prevent death.
  • Liver and red bone marrow can take over some function, however, immune function is compromised.
46
Q

Thymus

A
  • A bi-lobed organ that plays important role in immune development & antibody production in early life.
  • Contains epithelial cells, T-lymphocytes and macrophages.
  • Epithelial cells produce ‘thymosin’ which promotes the maturation of T-lymphocytes (produced in the red bone marrow).
  • T-cells that leave the thymus via the blood migrate to lymph nodes and other lymphatic tissueswhere they colonise.
  • Atrophy begins in puberty (age 12), declining throughout life –tissue is replaced by fat.
47
Q

Mucosa Associated Lymphoid Tissue (MALT)

A
  • Small aggregations of lymphoid tissue found in areas of the body exposed to the external environment –‘first line of immune defence’.
  • MALT that is found in the digestive system is also called GALT(‘Gut Associated Lymphoid Tissue’).
  • Some examples where MALT can be found:
  • Adenoids (MALT but not GALT as found in nasal cavity not GIT).
  • Tonsils.
  • Small intestine and large intestine.
48
Q

Lymphatic System Functions

A
  1. Tissue Drainage
  2. Absoption
  3. Immunity
49
Q

Lymphatic System Functions: Tissue Drainage

A
  • Blood arrives at the tissue at high pressure so some of the fluid & nutrients are forced out of the capillaries into the interstitial fluid.
  • The remaining cells & plasma proteins in the blood create an osmotic pressure which maintains blood volume. Tissue fluid is at lower pressure.
  • Interstitial fluid contributes to the nourishment of tissues. 90% returns to circulation via veins.
  • The lymphatic system is responsible for draining and recirculating this extra fluid and returning it to the blood stream
  • Lymphatic fluid is drained with assistance of this following:
  • Mild, rhythmical contractions of the lymphatic vessels (lymphatic pump).
  • Skeletal muscle pump: Movement/exercise drains fluid. Especially the calf muscles (gastrocnemius & soleus).
  • Respiratory pump: During inhalation air pressure drops in the thoracic region. Lymph moves from high to low pressure.
50
Q

Lymphatic System Functions: Absorption

A
  • Lacteals absorb fat-soluble substances/nutrients from the small intestines in to the body:
  • Dietary fats.
  • Fat-soluble vitamins (A, D, E & K).
51
Q

Lymphatic System Functions: Immunity

A
  • Lymph organs are concerned withtheproduction and maturation of lymphocytes:
  • Lymph nodes.
  • Spleen.
  • Thymus and Bone marrow.

Biomedicine I (18 decks)

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