term test 2 Flashcards

1
Q

kidney location

A
  • located at dorsal lumbar area outside of the abdomen , between peritoneum and dorsal abdominal muscles outside the peritoneal cavity
  • right kidney more cranial than the left in most domestic animals
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

gross anatomy of kidney

A
  • bean-shaped structure
  • in cattle , it is lobulated
  • hilus
  • renal pelvis
  • renal cortex
  • renal medulla
  • calyx
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

hilus - kidney

A
  • indented area in medial side
  • where ureters , nerves , blood and lymph vessels enter and leave the kidney
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

renal pelvis - kidney

A
  • funnel-shaped area
  • beginning of ureter
  • collects urine produced by renal cortex before it travels through the ureter into the bladder
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

renal cortex and renal medulla - kidney

A

renal cortex ;
- outer portion of kidney

renal medulla ;
- inner portion around renal pelvis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

calyx / calyces - kidney

A
  • cup-like structure
  • formed when renal pelvis extends into the medulla pyramid
  • directs and collects fluids into renal pelvis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

microscopic anatomy of kidney

A
  • basic functional unit : nephron

each nephron consists ;
- renal corpuscle
- proximal convoluted tubule (PCT)
- loop of henle (LOH)
- distal convoluted tubule (DCT)

renal corpuscle -> PCT -> LOH -> DCT -> urine

  • some parts of a nephron eg renal corpuscle are only in the cortex while others eg loop of henle is only in the medulla
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

renal corpuscle

A
  • located in renal cortex
  • glomerulus / glomerular tuft ; cluster of capillaries
  • bowman’s capsule ; surrounds the glomerulus to hold the capillaries
  • capsular space / bowman’s space ; between capsule and glomerulus , there is a space
  • filters blood in the first stage of urine formation
  • fluid that is filtered OUT of blood through capillaries and into capsular space = glomerular filtrate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

blood supply into glomerulus

A
  • renal artery enters kidneys at the hilus , dividing into smaller arteries and even smaller arterioles
  • afferent glomerular arterioles carries blood into glomerular capillaries of renal corpuscle
  • glomerular capillaries filters some plasma out of the blood into the bowman’s space and it becomes glomerular filtrate
  • efferent glomerular arterioles receives blood from glomerular capillaries
  • A goes in , E goes out
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

proximal convoluted tubule (PCT)

A
  • continuation of capsular space
  • twisting path through the cortex
  • when glomerular filtrate enters the PCT from the capsular space , it becomes tubular filtrate
  • where 65% of reabsorption takes place
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

loop of henle (LOH)

A
  • long , u-shaped portion of the tubule
  • descends from PCT into medulla (descending LOH)
  • turns and heads upwards back into the cortex (ascending LOH)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

distal convoluted tubule (DCT)

A
  • DCT is the continuation of the ascending LOH
  • DCT of all nephrons will drain urine into collecting ducts
  • collecting ducts carries tubular filtrate (which is now waste products only / urine) through the medulla and empties into renal pelvis
  • primary site of action of ADH (antidiuretic hormone)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

reabsorption in the tubules is possible because …

A
  • efferent glomerular arterioles divide to form peritubular capillaries (small capillaries that surround the tubules)
  • allows oxygen supply to the tubules , tubular reabsorption , tubular secretion
  • peritubular capillaries will converge at the end to form a larger vein (renal vein)
  • renal vein leaves the kidney at the hilus to join the caudal vena cava
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

3 steps of urine formation

A
  • kidney filters unwanted substances to excrete them
    1. glomerular filtration
    2. tubular reabsorption
    3. tubular secretion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

glomerular filtration

A
  • glomerular capillaries are permeable (not enough to allow blood cells and large proteins to pass through)
  • plasma proteins and substances such as calcium that are bound to them are unable to pass
  • fluids leave bloodstream into capsular space
  • in glomerular capillaries , blood pressure is very high and forces some plasma out into capsular space
  • glomerular filtrate = primitive urine (first stage)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

glomerular filtrate

A
  • fluid that passes through glomerular capillaries into capsule space
  • any product that is smaller than plasma protein or freely dissolved in plasma appears in glomerular filtrate
  • eg sugars , amino acids , toxins
  • glomerular filtrate in the capsule space will move on to the next section of the renal tubule (proximal convoluted tubule PCT)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

reabsorption

A
  • ensures the body gets back small useful molecules from the filtrate
  • eg amino acids , peptides , glucose , water , Na+ , Cl-
  • substances to be reabsorbed pass through the tubular lumen , tubular wall and capillary wall back into the bloodstream
  • 65% of reabsorption takes place in the PCT , and remaining in the DCT / LOH
  • 80% of water , sodium chloride & bicarbonate are reabsorbed
  • 100% of glucose & amino acids are reabsorbed [if they are detected in the urine , it could suggest problems]
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

sodium / glucose & amino acid / potassium & calcium / chloride / water reabsorption

A

sodium ;
- PCT , LOH , DCT

glucose & amino acid ;
- PCT

potassium & calcium ;
- PCT

chloride ;
- diffuses through in response to an imbalance created by sodium reabsorption
- moves with sodium

water ;
- follows ions through osmosis
- once sodium , glucose , amino acids & chloride have left tubular filtrate , water molecules follow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

antidiuretic hormone (ADH) - urinary

A
  • ADH from pituitary gland
  • acts on DCT to promote water reabsorption
  • tells DCT to reabsorb more water
  • concentrates urine
  • released when an animal is dehydrated or hypotensive to increase water content in the blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

alosterone

A
  • from adrenal cortex
  • acts on DCT to increase reabsorption of sodium
  • tells DCT to reabsorb more sodium
  • more sodium reabsorbed = osmotic imbalance = water molecules follow
  • concentrates urine
  • Na+ reabsorbed = K+ secrete
  • if sodium is taken in, must be replaced by potassium to maintain salt balance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

tubular secretion

A
  • substances from blood capillaries move into tubules / urine
  • substances not filtered in the glomerulus eg urea , ammonia OR due to reabsorption of sodium eg potassium , hydrogen for salt and acid-base balance
  • occurs in PCT , LOH and DCT
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

renin - osmoregulation

A
  • hormone secreted in glomerulus in response to low arterial pressure
  • if pressure is low , glomerulus cannot filter blood to form glomerular filtrate
  • converts angiotensinogen into angiotensin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

angiotensin - osmoregulation

A
  • vasoconstriction to raise blood pressure
  • the constriction stimulates the release of aldosterone from adrenal cortex , causing water to be reabsorbed into the bloodstream
  • more water = higher pressure = glomerulus able to filter blood to form glomerular filtrate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

ureters

A
  • leavers kidney at the hilus
  • has 3 layers :
    1. outer fibrous
    2. middle smooth muscle (propels urine by peristaltic contractions)
    3. inner layer lined with transitional epithelium (allows ureters to stretch as urine passes through)
  • enters urinary bladder at oblique angle , forming a valve to prevent back flow
  • when bladder is full , urine presses on the entrance to close the valve
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
urinary bladder
- lined with transitional epithelium , can stretch as it is filled - wall of the urinary bladder has smooth muscle - around the neck of the urinary bladder , there are sphincter muscles
26
sphincter muscles
- internal sphincter : smooth muscles under involuntary control - external sphincter : skeletal muscle under voluntary control , allows control of urination - when the bladder is full , it sends a signal to the spinal cord which tells the smooth muscle / internal sphincter to tract - the contraction of the smooth muscle when the bladder is full , we get the urge to pee
27
urethra
- continuation of the neck of urinary bladder - carries urine from bladder to the external environment - lined with transitional epithelium that allows it to stretch - female ; shorter , straighter , only urinary function - male ; longer , curved , runs down centre of the penis and also carries semen
28
control of urination process
- urination = excretion of urine from urinary bladder to urethra to external environment - build-up of pressure in the bladder activates stretch receptors (senses pressure) in the bladder wall - stretch receptors activate spinal reflex that cause smooth muscles of the bladder to contract - contraction gives the sensation of needing to urinate - voluntary control of the external sphincter (skeletal muscle) around the neck of the bladder allows temporary control of the urination - house-trained animals exercise some form of voluntary control and temporarily hold urine (eg grass trained dogs) - however , beyond a certain pressure limit , the sphincter must relax to release the urine
29
formation of urine
filtration -> reabsorption -> secretion -> concentration -> excretion
30
mitosis
- cell division that results in 2 daughter cells each having the same number and kind of chromosomes as the parent cell - aka diploids - daughter cells are identical to each other and parent cell - typical form for tissue growth , but NOT for sperm and ovum .
31
meiosis
- cell division that results in daughter cells each with half the number of chromosomes as the parent cell - aka haploids - daughter cells are not identical to the parent cell - sex cells eg sperm and ovum are produced this way - this ensures the fertilised egg from the union of sperm and ovum has the same number of chromosomes as a parent cell (half + half = one)
32
components of male reproductive system
- testes - dust system (epididymis , vas deferens , urethra) - external genetalia (penis , scrotum) - accessory glands (prostate gland , bulbourethral gland that dogs do not have , vesicle glands in rats only)
33
testes
- produces sperm cells and testosterone - "held" inside the scrotum , outside the abdomen as normal internal body temperature is too high for sperm development - concentration of testosterone influences the development of sperm and other male secondary sexual characteristics (eg bigger body, having penis and testes)
34
testes microscopic
- seminiferous tubules ; coiled mass of tubules , produces sperm - seminiferous tubules eventually combine / join to form epididymis (a long convoluted tubule) - interstitial cells ; between the tubules , secretes testosterone
35
scrotum
- skin pouch that houses testes - regulates temperature of testes - maintains testes at 3 degrees celsius lower than normal body temperature to protect sperm's viability - 2 muscles attached to the scrotum : cremaster and dartos , pull scrotum close to the body when it is cold and relax when it is warm
36
epididymis
- highly convoluted duct , caudal to testes - tail of epididymis continues as vas deferens (epididymis eventually converge to form vas deferens . sperm goes from epididymis to vas deferens to prostate , urethra and out) - sperm that is formed in the seminiferous tubules will mature as they pass into the epididymis - sperm is stored in the epididymis before they are propelled along vas deferens during ejaculation
37
vas deferens
- aka ductus deferens - carries sperm quickly from epididymis to urethra during ejaculation
38
penis
- urethra surrounded by layers of erectile tissue , muscle and connective tissue - erectile tissues have many holes where blood can enter to erect the penis , enabling entry to the vagina - penis has rich blood supply with many nerve endings - delivers semen (sperm + fluids) from the testes into the female reproductive tract during mating - also expels urine from the bladder to the outside via urethra
39
os penis
- embedded in erectile tissue close to the tip is the os penis - os penis allows the entry of the penis into the vagina before erection is fully complete
40
accessory glands
- semen = sperm + fluid - fluid = secretions from various accessory glands - alkaline fluid (includes electrolytes, etc) to protect the sperm by counteracting the acidity of the female reproductive tract * vagina = acidic , good for female's health but hard for sperm to survive . alkaline fluid counteracts that - different species have different combinations of accessory glands
41
prostate gland
- present in all domestic animals - particularly large in dogs
42
bulbourethral glands
- only in cats and a few other animals
43
seminal vesicle glands
- not present in dogs and cats - rats have
44
components of female reproductive system
- ovary - uterine tube - uterus (uterine horns , uterine body) - cervix - vagina - vulva
45
ovaries
- lies on each side of the dorsal part of the abdominal cavity (very close to kidneys) - produces ova/eggs - produces oestrogen during follicle development stage and preparing for mating - products progesterone to prepare for and maintain pregnancy by creating a comfortable environment in uterine lining - contains primary follicles which develop into mature follicles - number of follicles in a female is fixed from birth
46
primary follicles
- within ovarian connective tissue - contains an immature ovum surrounded by a single layer of follicular cells - each follicle has only one egg cell - can develop into a mature follicle
47
mature follicle
- contains small amount of fluid and an ovum - each follicle has only one egg cell
48
oviduct
- aka uterine tube / fallopian tube - small tubes that extend from the tips of uterine horns - finger-like projections at the tip known as fimbriae which capture the ovum released from ovaries - also a site for fertilisation (sperm -> vagina -> cervix -> uterus -> oviduct -> meets ovum) - cilia inside the oviduct move the fertilised ova slowly through uterine horns towards the uterus - fertilised = embeds in uterus = pregnant - not fertilised = still pushed eventually - collects ova as they are released from ovaries - conveys ova from ovaries to the uterine horns - provide correct environment for the survival of both ova and sperm to aid fertilisation
49
uterus
- Y-shaped (horns and body) 3 walls ; 1. endometrium 2. myometrium 3. perimetrium - provides a new site where embryos can develop into a baby - provides means for developing embryos to receive nutrients from the mother via placenta / umbilical cord
50
endometrium - uterus
- inner mucosal layer - a lot of blood supply - secretes mucous and other substances - allows implantation of a fertilised egg - this layer thickens during pregnancy to provide nutrition to the embryo and support the development of the placenta - nutrients from mother's blood vessels -> placenta -> embryo
51
myometrium - uterus
- middle layer , smooth muscle - strong contractions during parturition - assists in pushing the baby out
52
perimetrium - uterus
- outer visceral layer of peritoneum - suspends uterus from the dorsal body wall - fixes uterus in its position
53
cervix
- short , thick-walled muscular sphincter - connects uterine body with vagina - lumen / inside space = cervical canal - it is normally tightly closed to prevent uterine infections , only dilating to allow sperm or foetus to pass - during pregnancy , cervical canal is blocked by a mucous plug which ensures bacteria and foreign particles cannot go in , protecting the embryo from infections
54
vagina
- a tube that leads to the external opening - receives the penis at breeding - serves as birth canal at birth
55
vulva
- external part of the female reproductive system - guarded by a pair of vertical labia - lying between the labia is a knob of erectile tissue aka clitoris
56
uniparous species
- one mature ovum produced per cycle only - rare to have more - humans , horses , cows
57
multiparous species
- multiple ova produced per cycle - big litters - cats , dogs , sow
58
ovarian cycle
- starts with primary follicle with an immature ovum in the centre - follicle stimulating hormone (FSH from pituitary gland) stimulates selected follicles to mature - as follicle grows , fluid holes form and continue to "merge" and get larger (more fluid) - when the follicle and ovum have reached the maximum size , it is considered fully mature . - oestrogen will be produced by follicular cells to assist in stimulating the release of the ovum - luteinising hormone from pituitary gland is released and ovulation occurs as a result - the surface of a mature follicle will weaken and rupture , releasing the ovum along with fluid into the oviduct - empty follicle fills with blood after the ovum is released - after an ovum has left the follicle , the empty follicle develops into corpus luteum - if there is pregnancy , the corpus luteum is maintained through an endocrine signal - if no pregnancy , the corpus luteum regresses - cycle ends when corpus luteum has regressed.
59
corpus luteum
- after an ovum has left the follicle , the empty follicle develops into corpus luteum - the process is influenced by the stimulation of luteinising hormone - produces progesterone - if there is pregnancy , the corpus luteum is maintained through an endocrine signal - if no pregnancy , the corpus luteum regresses
60
progesterone
- necessary to maintain pregnancy - thickens uterine lining and prepares for the implantation of fertilised egg - allows fertilised egg to grow comfortably - lack of progesterone may cause an unfavourable condition for the egg and may result in miscarriage
61
4 stages of estrous cycle - bitches
- proestrus (approx 9 days) - estrus (approx 9 days) - metestrus / diestrus (if not pregnant , 90 days. if pregnant , 50-60 days , delivery at approx 63 days after ovulation) - anestrus (5 months)
62
proestrus - bitches
- initial phase, approximately 9 days - body prepares for potential mating and pregnancy - females release pheromones to attract males , but mating does not take place yet - increased oestrogen in the blood (relate to maturation of follicles and ovarian cycle) - oestrogen helps the body to prepare - swelling of vulva - bloody vulval discharge
63
estrus - bitches
- when follicle is mature enough to release the ovum - approximately 9 days - females become receptive to mating - may actively seek out males and exhibit behavioural changes eg restlessness , changes in appetite , and increased frequency of urination - oestrogen declines and luteinising hormone reaches its peak level - triggers ovulation (releasing ovum) - if a female mates with a male , fertilisation can take place - corpus luteum forms in place of the empty follicle - regress if not pregnant - maintain and secrete progesterone if pregnant
64
metestrus / diestrus - bitches
- approximately 60-90 days - if fertilisation has occurred , corpus luteum maintains and produces progesterone - if no fertilisation has occurred , corpus luteum regresses and the female will enter a non-pregnant diestrus phase where uterus returns to the normal state
65
anestrus - btiches
- several months - lack of ovarian activity , reproductive system rests before the next cycle begins - if not pregnant , progesterone level gradually declines - when a new cycle is about to start , some primary follicles will begin to develop
66
fertilisation
- ovum + sperm = fertilisation = zygote - sperm is propelled up the ductus deferens into the urethra , through the penis and into the female reproductive tract - sperm "swim" from the vagina through the cervix into the uterus - once a sperm penetrates the ovum , further sperms are prevented from entering due to a rapid chemical change that thickens the ovum's surface - zygote = diploid = ready for mitosis
67
pregnancy
- after fertilisation , zygote undergoes mitosis - as it is dividing , it also moves along the oviduct - once it reaches the uterine horn , it has many cells and a fluid cavity ; it is now known as a blastocyst - blastocyst implants in the uterine horn and continues to divide - endometrium and myometrium are thickened by progesterone = new blood vessels grow and mucous secretes = more nutrients and comfortable for blastocyst to maintain pregnancy - increased progesterone - physical changes eg weight gain , enlargement of abdomen and development of mammary glands
68
stage 1 of parturition
- can last up to 24 hours - restless , nesting behaviour - decreased body temperature - uterine contractions - cervix gradually dilates to allow the passage of puppies
69
stage 2 of parturition
- can last up to a few hours to a full day - active delivery - uterine contractions intensify and female dog must push to deliver each puppy - puppies are enclosed in individual amniotic sacs which may rupture during delivery - mother typically breaks the sac , cleans the puppies and stimulates their breathing - interval between each puppy can vary , but it usually ranges between 10 minutes to an hour
70
stage 3 of parturition
- involves the delivery of the placenta - placenta nourished and protected puppies during gestation - female dogs may eat the placenta which is natural as it can provide nutrients and clean the whelping area
71
major endocrine glands in cats
- pituitary gland - thyroid gland - parathyroid gland - pancreas - ovaries - testes - adrenal glands
72
mechanisms controlling hormone secretion
- nerve impulses (eg adrenaline from adrenal gland in response to nerve impulses from sympathetic nervous system) - stimulating or releasing hormone (eg secretion of thyroid hormone is controlled by thyroid stimulating hormone from pituitary gland) - levels of certain chemicals in the blood (eg glucose high , pancreas releases insulin) - negative feedback system (eg oestrogen secreted after the follicle has matured prevents further secretion of FSH from pituitary gland)
73
pituitary gland
- small , ventral to the hypothalamus 2 portions with different functions and structure : - anterior pituitary (cranial portion) ; produces hormone - posterior pituitary (caudal portion) ; stores and releases hormones produced in the hypothalamus , does not produce any hormone
74
hormones released by pituitary gland (anterior pituitary)
- growth hormone - prolactin - thyroid-stimulating hormone (TSH) - adrenocorticotropic hormone (ACTH) - follicle-stimulating hormone (FSH) - luteinising hormone (LH) - interstitial cell stimulating hormone
75
growth hormone (GH)
- aka somatotropin hormone - promotes body growth in young animals - helps to regulate metabolism of proteins , carbohydrates and lipids
76
prolactin
- triggers and maintains lactation (secretion of milk from mammary glands) - if nipple is stimulated by nursing , prolactin will continue to be released
77
thyroid-stimulating hormone (TSH)
- stimulates the development of the thyroid gland - stimulates the thyroid gland to produce thyroid hormone
78
adrenocorticotropic hormone (ACTH)
- stimulates the growth and development of the adrenal gland - stimulates the release of hormones from the adrenal gland (eg cortisol) - in sudden stress , hypothalamus is stimulated and ACTH is released very quickly (cortisol -> signs of nervousness eg heart beating fast)
79
follicle stimulating hormone (FSH)
- female : growth and development of ovarian follicles (source of ovum) - also stimulates follicular cells to secrete oestrogen (more oestrogen = negative feedback = less FSH) - male : acts on tubules of the testis to aid sperm production
80
luteinising hormone (LH)
- stimulated by the presence of oestrogen in the blood - stimulates mature follicles to rupture and release their ovum - signals the empty follicle to form yellow body / corpus luteum
81
interstitial cell stimulating hormone (ICSH)
- stimulates the interstitial cells in the testes to secrete testosterone when concentration is low in the body
82
hormones stored and released by the pituitary gland (posterior pituitary)
- does not produce hormones - only stores and releases hormones produced by the hypothalamus - antidiuretic hormone (ADH) - oxytocin
83
antidiuretic hormone (ADH) - endocrine
- acts on kidney - reabsorbs more water from the urine and returns it to the bloodstream (more concentrated urine) - released when the receptor in the hypothalamus detects a change of osmotic pressure in the blood due to dehydration
84
oxytocin - endocrine
- acts on mammary glands during late pregnancy - causes milk to be released in response to a neonates suckling - at the end of gestation , oxytocin causes the contraction of the smooth muscle of the uterus which results in parturition of the foetuses
85
thyroid gland
- ventral to first few rings of the trachea - triiodothyronine (T3) - thyroxine (T4) - they regulate metabolic rate of body cells and are essential for normal growth - allows animal to generate heat , maintain a constant internal body temperature and maintain blood glucose * if metabolic rate is too high , nutrients are used too fast , body produces a lot of heat ** if metabolic rate is too low , nutrients are used too slow and body weight will increase with just a bit of eating . body doesn't produce enough heat - calcitonin
86
calcitonin
- regulates calcium level in the blood (together with parathyroid hormone) - lowers calcium levels by inhibiting the rate of decalcification of bone and stimulating bone growth - tells bone not to release calcium into the blood and absorb more calcium from the blood
87
hypothyroidism
- undersecretion of thyroid hormones (especially T3 and T4) - stunted growth - hair loss - slow heart rate - fat - sluggish
88
hyperthyroidism
- oversecretion of thyroid hormones (especially T3 and T4) - hyperactive - aggressive - increased appetite - fast heart rate
89
parathyroid gland
- small nodules in , on or near the thyroid glands - parathyroid hormone (PTH / parathormone)
90
parathyroid hormone (PTH)
- maintain blood calcium levels - along with calcitonin - calcitonin deposits calcium from the blood into the bone when blood calcium levels are too high - parathyroid hormone reabsorbs calcium from the bone into the blood when blood calcium levels are too low
91
pancreas
- located in the curve of the duodenum - small islets inside the endocrine component have cells that secrete 3 hormones - beta cells : insulin - alpha cells : glucagon - delta cells : somatostatin
92
insulin
- produced by beta cells of the pancreas - response to high blood glucose - decreases blood glucose by increasing the uptake of glucose into the blood cells and storing excess glucose as glycogen in the liver - lack of insulin = diabetes mellitus , unable to lower blood glucose
93
glucagon
- produced by alpha cells of the pancreas - response to low blood glucose - signals liver to break down glycogen to release glucose
94
somatostatin
- produced by delta cells of the pancreas - inhibits the secretion of insulin and glucagon - if insulin / glucagon has finished their jobs and blood glucose has returned to regular levels , somatostatin inhibits their secretion
95
adrenal gland
- in a pair , at cranial ends of the kidneys - adrenal cortex (outer) and adrenal medulla (inner)
96
adrenal cortex (outer)
produces : - aldosterone - glucocorticoids - sex hormones
97
aldosterone - endocrine
- acts on the kidney at the distal convoluted tubule (DCT) - increases reabsorption of sodium ions (water molecules follow to maintain balance) - more concentrated urine - regulates acid-base balance
98
glucocorticoids
- cortisone - corticosterone - low levels that increase in response to stress - increases blood glucose levels (that's why there may be hyperglycaemia during stress) - when present in large quantity , it depresses inflammation reactions
99
sex hormones
- androgens (male) - oestrogen (female) - both are present in all animals , but the opposite sex hormones will be in small quantities with minimal effect - concentration is important : low testosterone will cause tiredness
100
adrenal medulla (inner)
produces : - epinephrine - norepinephrine - prepares the body for emergency action / fight or flight - secretion is controlled by the autonomic / sympathetic nervous system (involuntary)
101
functions of epinephrine and norepinerphrine
- raise blood glucose levels by breaking down glycogen in the liver (increases energy levels) - increase heart rate and respiration (meet high demand of oxygen in times of stress) - dilate blood vessels (increase supply of glucose and oxygen) - decrease the activity of the GI tract and bladder (as they are less important in stress)
102
ovaries - endocrine
- oestrogen - progesterone - relaxin
103
oestrogen
- prepares animal for mating - prepares body to produce follicles and release ovum - causes behaviour associated with estrus cycle - prepares reproductive tract and external genetalia for mating
104
relaxin
- produced by ovaries in later stages of pregnancy - softens and relaxes ligaments around the birth canal - prepares for parturition and foetus delivery
105
testes
- testosterone
106
testosterone
- produced in response to ICSH (interstitial cell stimulating hormone) from anterior pituitary gland - leads to the development of male characteristics - muscle development - male behavioural patterns - development of sperm
107
nervous system
- brain , spinal cord , sensory organs and all of the nerves that connect these organs with the rest of the body - allows an animal to respond in coordinated manner to both the demands of the external environment and internal changes within the body
108
3 functions of the nervous system
- receive information / stimuli from external and internal environments via sensory nerves - analyse and integrate these stimuli from the sensory pathway to the central nervous system (CNS) - after a response has been decided , motor nerves send a signal to initiate response of effector
109
movement of nerve impulses
sensory nerves receive stimulus -> CNS analyse stimulus -> makes decision what to do -> motor nerves initiate response according to CNS decision
110
peripheral nerves
- cranial nerves - spinal nerves (sensory and motor) - autonomic nervous system (sympathetic and parasympathetic)
111
central nervous system
- brain - spinal cord
112
sensory nerves
- carries information into the central nervous system - has 2 types - somatic : receives stimuli from external environment ; skin , muscle , joints , eyes , voluntary control (eg seeing a snake) - visceral : receives stimuli from internal environment ; internal organs , glands , blood vessels , involuntary control (eg stomach sends message to CNS that more gastric juice is needed when food is consumed , prompting gallbladder to prepare to release bile and liver to prepare for digestion)
113
motor nerves
- carries information from the central nervous system - somatic nervous system : voluntary , skeletal muscles (eg hand movements) - autonomic nervous system : involuntary , cardiac muscles , smooth muscles , glands (eg make heart beat faster) - autonomic nervous system has 2 divisions ; sympathetic and parasympathetic
114
sympathetic nervous system
- controls body in times of stress (eg seeing a snake = stimulates adrenal glands to secrete adrenaline) - opposite effect on organs compared to parasympathetic nervous system - dilate pupils - inhibit saliva - increase heartbeat - relax airways - inhibit stomach activity - stimulate release of glucose - inhibit gallbladder - inhibit intestinal activity - relax bladder - promote ejaculation and vaginal contraction
115
parasympathetic nervous system
- controls body in times of rest (eg during sleep) - opposite effect on organs compared to sympathetic nervous system - constrict pupils - stimulate saliva - slow heartbeat - constrict airways - stimulate stomach activity - inhibit release of glucose - stimulate gallbladder - stimulate intestinal activity - contract bladder - promote erection of genitals
116
cells of the nervous system
- neurons / nerve cells - gila / glial cells are support and protect neurons
117
structure of neurons
- dendrite branch out from dendron to receive stimuli - cell body : soma ; has nucleus , cell membrane - long structure / tail : axon - bundle of axons is called a nerve fibre - schwann cells protect the axon by secreting myelin - forms a myelin sheath
118
glial cells
- many types - schwann cells (PNS) - oligodendrocytes (CNS) - both are responsible to myelin sheath that facilitates impulse transmission in an axon - multiple glial cells cover the length of an axon - there are small gaps between each glial cell (nodes of ranvier) - myelin is insulating and thus nerve impulses jump from node to node and are conducted through the axon at a much faster speed
119
grey and white matter - nervous system
- myelin wrapped axons appear white - unmyelinated axons , dendrites and cell body will appear grey
120
action potential
- electrical signal that allows nerve impulses to spread along the axon of a neuron - generation process involves several membrane mechanisms : - resting membrane potential - depolarisation - resting phase - repolarisation - hyperpolarisation
121
resting membrane potential
- resting status , no need for action potential - charge inside of the neuron is negative relative to the outside (mainly due to the distribution of different ions on each side) - the difference between the charges on the inside and outside = resting membrane potential - typically around -70 mV - outside of cell : positive , a lot of positively charged sodium ions - inside of cell : negative ; some positive ions (eg potassium) but much less than outside , negatively charged proteins - ion channels ; voltage-gated (important in nervous system context) , Ligand-gated , mechanically gated
122
depolarisation
- polar = outside positive , inside negative - depolarisation = remove polar situation / difference in charge between the 2 sides - positive must enter and negative must leave - when a neuron receive a strong enough signal or signal from a neighbouring neuron , sodium ion channels open temporarily and allow sodium ions to rush into the neuron - influx of positive charge in the neuron (less negative inside , depolarising) - charge inside the neuron will reach a peak (30 - 40 mV) and sodium will stop coming in. - depolarisation leads to activation of the neuron - as ion channels along the axon receive stimulus , they open - thus , the signal can pass to the end of the axon (depolarisation excites node of ranvier 1 , action potential , excites node of ranvier 2 , etc)
123
rising phase , generating action potential
- rapid influx of positively charged sodium ions leads to a sharp rise in membrane potential - reverse polarity - inside becomes more positively charged than the outside - creates action potential (AP) - depolarised neurons have AP which generates electrical impulse that travels along the axon
124
repolarisation
- after the charge inside the neuron reaches its peak of 30 - 40 mV - potassium ion channel opens - potassium ions inside the cell go out - positive charge ions go out and the inside becomes more negative - sodium ions inside the cell may also be used by the cell after some time - cell goes back to its negative resting potential
125
hyperpolarisation
- in some neurons , the escape of potassium ions can briefly cause membrane potential to be more negative than resting membrane potential - usually short lived
126
conduction of action potential between the neurons
- happens at synapse : end of an axon / start of another neuron (gap between 2 neurons) - when action potential reaches the end of the axon (terminal) , translated to chemical signals / neurotransmitters - receptors on the dendrite of the next neuron are stimulated by neurotransmitters - the next neuron is activated , and a new AP would be generated in the next neuron
127
types of neurotransmitters
- excitatory neurotransmitters - inhibitory neurotransmitters
128
excitatory neurotransmitters
- causes influx of sodium so that neurons will be depolarised - acetylcholine - norepinephrine - epinephrine - dopamine - serotonin - glutamate
129
inhibitory neurotransmitters
- causes entry of chloride ions which lead to hyperpolarisation (when hyperpolarised, cell will not pass a signal) - gamma-aminobutyric acid (GABA) - glycine
130
brain - central nervous system
- cerebrum (typically left and right cerebrum , cerebral cortex) - diencephalon (thalamus , hypothalamus) - brain stem (very important for life , midbrain , pons , medulla oblongata) - cerebellum (caudal to cerebrum)
131
cerebrum - brain
- controls conscious activities , intelligence , memory , language and muscles
132
cortex - brain
- organised into different functional regions - highly developed (especially in humans) - in higher species (eg humans) , the cortex has a bigger surface area due to folds - functional regions : sensory , motor areas , auditory areas , visual areas , higher functional areas (eg prefrontal cortex in humans)
133
functional regions in the cortex - brain
- sensory : receive somatic sensory information from different parts of the body - motor : initiate / coordinate motor activity in the muscles - auditory : receive hearing information from the ears - visual : receive visual information from the eyes - higher functional areas (eg prefrontal cortex in humans) : solving complex tasks
134
cerebellum - brain
- responsible for coordination of movement , balance and posture - if damaged , may not be able to move in a straight line and movements become jerky
135
brain sterm
- medulla oblongata , pons , midbrain - responsible for vital life functions - breathing , heartbeat , blood pressure - many cranial nerve pairs originate from the brain stem
136
diencephalon
- below the cerebrum - relay station between brainstem and cerebrum - thalamus : relay station for sensory inputs to the cerebrum - hypothalamus : interface between nervous system and endocrine system
137
protection of the CNS
- CNS protected by cranium , vertebral column and meninges
138
cranium
- bones of the skull - hard outer covering to the brain
139
meninges
- coverings of the brain and spinal cord - 3 layers of membrane (surface , middle , deep) - dura mater : double-layered , periosteal and meningeal , external covering blow the bone of skull - arachnoid layer : middle , web-like layer - pia mater : internal layer
140
brain ventricles and fluid
- network of cavities within the brain - filled with fluid (CSF - cerebrospinal fluid) - CSF is in both the brain and spinal cord
141
cerebrospinal fluid (CSF)
- cushions the brain within the skull - shock absorber - circulates nutrients and chemicals - removes waste products from CNS - similar function to blood except it doesn't contain blood cells - composition is similar to blood plasma but without blood cells - circulated in brain ventricles and spinal cavity in the arachnoid space (space below the arachnoid layer of meninges)
142
cranial nerves
- 12 nerve pairs that originate from the brain stem - each nerve may contain axons of motor neurons , sensory neurons or a combination of both I - olfactory II - optic III - oculomotor IV - trochlear V - trigeminal VI - abducens VII - facial VIII - vestibulocochlear IX - glossopharyngeal X - vagus XI - accessory XII - hypoglossal
143
cranial nerve I
- olfactory - smell
144
cranial nerve II
- optic - sight
145
cranial nerve III
- oculomotor - moves eye and pupil
146
cranial nerve IV
- trochlear - moves eye
147
cranial nerve V
- trigeminal - face sensation
148
cranial nerve VI
- abducens - moves eye
149
cranial nerve VII
- facial - moves face - salivation
150
cranial nerve VIII
- vestibulocochlear - hearing - balance
151
cranial nerve IX
- glossopharyngeal - taste - swallow
152
cranial nerve X
- vagus - heart rate - digestion
153
cranial nerve XI
- accessory - moves head
154
cranial nerve XII
- hypoglossal - moves tongue
155
spinal cord
- consists of well-organised nerve fibres running in tracts - uniform structure throughout entire length - myelinated outer white matter surrounding central unmyelinated grey matter - enveloped by meninges and surrounded by cerebrospinal fluid (CSF) - CSF also flows within the central canal
156
cross-section of the spinal cord
- grey matter displays a distinctive "butterfly" shape - dorsal horns / nerve roots ; houses cell bodies of the sensory neurons (smaller than motor) - ventral horns / nerve roots stand out ; houses cell bodies of the large motor neurons - central canal : continuation of brain ventricle , filled with CSF (cushioning , shock absorber , etc)
157
reflexes
- involuntary and nearly instantaneous movement in response to a stimulus - eg pulling your finger back from a hot object - reflex arcs which are organised at spinal cord level without involvement of the brain - response is very fast and doesn't go through the brain , protecting the body from potential harm due to the short neuronal circuit
158
neuronal circuit in reflexes
- when your hand touches something very hard , - sensory neurons forward sensory information to the spinal cord via dorsal nerve root - motor neurons in spinal cord forward information to the muscle via ventral nerve root - muscle are effectors that quickly remove the hand from the hot object.
159
reflex arc
- receptor , nerve endings in the skin that receive the sensation - sensory neuron passes information to the spinal cord via dorsal nerve root - spinal cord quickly decides what action to take - motor neuron passes information to the muscles via ventral nerve root - muscles are effectors that perform the action
160
taste buds
- organs responsible for taste - chemical receptors on dorsal side of the tongue receive chemical signals from food - chemical signals stimulate taste cells to produce a signal - connected to nerve endings / sensory nerves , which send the signal to CNS - 2 types : taste cell , surrounded by supporting cell
161
which nerves carry taste information to the brain?
- cranial nerves IX (9 - glossopharyngeal) and VII (7 - facial) - facial nerve carries taste information from the FRONT of the tongue to the brain - glossopharyngeal nerve carries taste information from the BACK of the tongue to the brain
162
sense of smell
- made possible by olfactory epithelium covering the naval cavities - odour molecules move in the air - when the molecules contact their specific receptors , it can be translated into a signal - odorant -> receptors that match its shape -> chemical reaction within the receptor cell - activated receptor cell sends nerve impulse - impulse travels through olfactory nerve (I) to the olfactory bulb
163
structure of the eyes
- outer fibrous layer (sclera - consists of sclera and cornea) - middle layer (uvea - consists of iris , ciliary body , choroid) - inner nervous layer (retina - consists of retina)
164
sclera
- white layer surrounding the eyes - connects with cornea to form outer sclera layer
165
cornea
- dome-shaped structure covering the pupils / iris area - connects with sclera to form outer sclera layer
166
iris
- controls amount of light entering the eye - contraction of radial and circular smooth muscles to control the size of pupil (circular contract = smaller , radial contract = dilated) - coloured part of the eye
167
ciliary body
- contains ciliary muscles muscles that attach the suspensory ligaments of the lens - pulls the suspensory ligament attached to the lens to control thickness and shape - contract = lens thinner , relax = lens thicker
168
suspensory ligaments
- continuation of ciliary body - suspends the lens
169
choroid
- pigmented vascular layer - layer right beneath the sclera - presents light from escaping the retina by bouncing it back to the retina - ensures retina receives most of the light
170
retina
- receives light / image signal - contains photoreceptor cells (rods and cones)
171
rod cells (in retina)
- functions well under dim light - not sensitive to colour - responsible for light of different intensity (black and white , night vision)
172
cone cells (in retina)
- functions well under bright light - responsible for colour vision
173
image formation
- light rays pass through the cornea , iris , lens and vitreous body - lens helps to focus the light rays onto the retina by adjusting the thickness of the lens (inverted image) - photoreceptor cells on the retina generate nerve impulses - image signal is sent to the optic nerve (cranial nerve II) - optic nerve sends it to the brain's visual cortex where the image is interpreted
174
vitreous body
- very clear , jelly-like structure in the middle of the eye that gives the eye its shape - works with aqueous humour to provide nutrients to the structures in the eye and maintain the shape of the eye
175
conjunctiva
- a very thin , transparent layer surrounding the outer surface / sclera - squamous epithelium - also the inner layer of the eyelid
176
limbus
- connection point between the cornea and sclera
177
anterior / posterior chambers
- iris divides the space between the lens and cornea into anterior and posterior chambers - posterior = very small (between iris and lens) - anterior = bigger (between iris and cornea) - chambers are filled with aqueous humour
178
aqueous humour
- fluid secreted by the ciliary body - works with vitreous body to provide nutrients to the structures in the eye and maintain the shape of the eye
179
circulation of aqueous humour
- watery fluid produced by ciliary body and secreted into posterior chamber - flows over the surface of the lens - circulates through the pupil - drains into canal of Schlemm in the anterior chamber - important to maintain the pressure of the eye and provide nutrients for the lens and cornea that have no blood vessels
180
myopia
- short-sightedness - image falls in front of the retina - cannot see objects that are far away clearly - due to abnormality in the lens that could be caused by any factors e.g. age or injury
181
hyperopia
- long-sightedness - image falls behind the retina - cannot see objects that are nearby clearly (far away objects appear more clear) - due to abnormality in the lens that could be caused by any factors e.g. age or injury
182
eyelids
- protects the eye - external surface covered by a thin , folded skin - internal surface covered by a smooth conjunctiva (a very thin membrane)
183
meibomian glands / tarsal glands
- opening is directly on the edge of the eyelid - produces oily tears (not watery tears) - these tears float on the surface of watery tears , preventing evaporation and making sure eyes do not dry out
184
tear apparatus and pathway of tears
- tears are produced in the tear (lacrimal) gland - disperses across corneal surfaces - enters the tear duct (lacrimal canaliculi) at punctum - enters nasal cavity via nasolacrimal duct
185
external / outer ear
- pinna - external auditory canal
186
pinna
- outer portion of the ear - the part we can see - mainly elastic cartilage and skin
187
external auditory canal
- carries sound waves to tympanic membrane / eardrum
188
middle ear
- air filled cavity - ear drum - 3 small ossicles in the cavity behind the ear drum (malleus , incus , stapes)
189
ear drum
- paper-thin membrane - vibrates when a sound wave strikes it
190
3 small ossicles
- malleus , incus and stapes - amplify and transmit sound vibrations from external to inner ear - when the sound from the external ear reaches the middle ear , the ear drum starts vibrating and this vibration is passed to the ossicles
191
inner ear
- eustachian tube in a small , fluid filled cavity deep within the skull : - cochlea - vestibular system
192
eustachian tube
- connects middle ear cavity with the pharynx - balances air pressure on the 2 sides of the ear drum
193
cochlea
- coiled , snail-shell-shaped structure - lined with sensory cells called hair cells - hair cells convert sound vibrations into electrical signals - sensitive to different sound frequencies - information is transmitted via auditory nerve (cranial nerve VIII / vestibulocochlear)
194
sound perception
- sound vibrations travel through the external auditory canal to the ear drum - ear drum vibrates - vibration transfers to 3 ossicles which amplify vibrations to oval window on inner ear - when a vibration enters the cochlea from the middle ear , fluid in the cochlea vibrates - vibration of fluid causes hair cells to bend - bending of hair cells sends a signal to the cochlear nerve (cranial nerve XII / vestibulocochlear) - vestibulocochlear nerve sends the signal to the brain's auditory cortex where it gets translated to a sound
195
vestibular system
- responsible for balance and equilibrium - 3 semicircular canals (tiny fluid filled tubes) and otolith organs (utricle and saccule) - they contain fluid and sensory hair cells - fluid shifts when head shifts - movement of fluid bend hair cells - hair cells predict loss of balance and position of the head - sends signal to the cranial nerve XII vestibulocochlear nerve - the brain sends signal and the body adjusts movement - helps to stay balanced and oriented
196
integumentary system
- outer covering of the body - skin - hair - claws - footpads
197
skin
- largest organ of the body - barrier against external environment - perforated (where skin blends with mucous membrane) by mouth , anus , urinary orifice and vulva - 3 layers : epidermis , dermis and hypodermis
198
epidermis
- outermost layer - stratified epithelial cells - new cells are produced on the basal layer and reach the outermost layer as they get older , thus cells on the epidermis are usually already dead and contains a lot of keratin - no blood vessels - no nerves - 4 layers of cells : stratum basale , stratium spinosum , stratum granulosum , stratum corneum
199
stratum basal
- lowest / basal layer - newest cells
200
stratum spinosum
- 2nd lowest layer - spinous layer
201
stratum granulosum
- 2nd highest layer - granulated = older - granular cell layer
202
stratum corneum
- highest. layer - contains keratin , slightly hard - most cells are already dead
203
dermis
- dense connective tissue , collagen and elastin fibres - rich in blood vessels and nerve endings - includes hair follicles (a channel that hair grows from) , sebaceous glands and sweat glands
204
functions of the skin
- sensory (nerve endings to detect temperature , pressure , touch and pain) - protection (barrier between external environment and internal structures ; prevents entry of microorganisms and injury of organs , protects against damage from UV light and water loss , prevents absorption of harmful substances) - production (glands to produce secretion) - storage (fat ; important as it provides energy and keeps warm . mainly stored in the hypodermis layer) - thermoregulation (heat loss ; dilation of surface blood vessel = more blood flow = heat escapes quickly / sweating = loss of water = evaporation = cools skin surface . heat gain ; constriction of surface blood vessel = not much blood passes = heat cannot escape quickly = conserve heat . insulation ; fat under the skin prevents heat loss and hair traps warm hair) - communication ; skin produces pheromones for intraspecific communication , colour also provides communication eg when attracting a mate
205
sensory - skin function
nerve endings to detect temperature , pressure , touch and pain
206
protection - skin function
- barrier between external environment and internal structures - prevents entry of microorganisms and injury of organs - protects against damage from UV light and water loss - prevents absorption of harmful substances
207
production - skin function
- glands to produce secretion
208
storage - skin function
- fat ; important as it provides energy and keeps warm - mainly stored in the hypodermis layer)
209
thermoregulation - skin function
- heat loss ; dilation of surface blood vessel = more blood flow = heat escapes quickly - sweating = loss of water = evaporation = cools skin surface - heat gain ; constriction of surface blood vessel = not much blood passes = heat cannot escape quickly = conserve heat - insulation ; fat under the skin prevents heat loss - hair traps warm air
210
communication - skin function
- skin produces pheromones for intraspecific communication - colour also provides communication eg when attracting a mate
211
sebaceous glands
- surrounds the hair follicles and secretes sebum - forms a thin , oily , water-repellent layer over the skin surface - gives coat hair a shiny appearance - prevents bacterial growth on skin surface (has an aseptic function and can kill some microorganisms)
212
sweat glands (2 types)
- 1 type opens into hair follicle - other type opens onto skin surface - sweat evaporates to cool the body - sweat removes some waste from the body
213
tail glands
- dorsal surface at the base of the tail - rich with sweat and sebaceous glands - release of sweat and sebum give off a unique scent that allows for recognition and identification of individual animals
214
anal glands
- pair of glands on either side of the anus - has a small duct that opens into the anus - powerful smelling secretions - secretions coat faeces to cover it with a unique smell for territory marking and attracting a mate
215
structure of hair
- everything outside that can be seen = hair shaft - everything inside that cannot be seen = hair root - surrounding the hair root = hair follicle - deepest part of hair follicle = hair bulb - 2 layers holding the hair root = inner and outer root sheath - bottom of hair follicle where there is a cluster of dermal cells and blood vessels , provides nutrients to hair = hair papilla - pulls hair so it can erect = arrector pili muscle - nerve endings
216
arrector pili muscle
- small , smooth muscle - attached to each hair follicle - controlled by sympathetic nervous system (involuntary) - muscle contraction pushes the hair to an erect position (can be due to temperature , fear , aggression , etc)
217
growth cycles of hair (4 phases)
- anagen (growing) - catagen (transitional) - telogen (resting) - return to anagen
218
anagen phase
- growth phase - young hair cells divide to build hair - shaft lengthens - papilla attached to blood vessels provides nutrients
219
catagen phase
- transitional phase - hair is grown - hair follicle shrinks - hair follicle begins to detach from the blood vessels
220
telogen phase
- resting phase - hair stops growing - fully detaches from blood vessels
221
return to anagen
- new hair grows - papilla attaches to blood vessels - new hair shaft pushes out old hair shaft - sheds old hair
222
types of hair
- guard hairs - wool hairs - sinus hairs
223
guard hairs
- longer and coarser - prevent water from soaking into the coat - protect against mechanical damage
224
wool hairs
- softer and wavy - close to body surface - insulating layer to regulate body temperature
225
sinus hairs
- long , coarse hairs that extend beyond the body outside - e.g. whiskers - whiskers have nerve endings and are sensitive - they are connected to blood-filled sinuses with rich nerve supply - when they move , they stimulate nerve fibres and send a nerve impulse to the brain
226
claws
- beak shaped - 2 layers of epidermis - keratinised epidermis forms a hard outer covering of each claw - protects distal phalanges during walking and weight bearing - provides grip
227
claws of dog
- thick and strong
228
claws of cat
- fine - much sharper than a dog's - can be retracted into pockets of skin by an elastic ligament - used as a defensive weapon
229
forelimb footpads
- dog forelimb = 6 pads (4 digits , carpal pad , metacarpal pad) - cat forelimb = 7 pads (5 digits , carpal pad , metacarpal pad)
230
hindlimb footpads
- dog hindlimb = 5 pads (4 digits , metatarsal pad) - cat hindlimb = 5 pads (4 digits , metatarsal pad)
231
footpads
- contains thick layers of fat and connective tissue - outer surface has the toughest and thickest skin in the body - protects underlying joints - acts as shock absorbers